Materiology: The Creative Industry's Guide to Materials and Technologies 9783038210801

Table of contents :
Contents
Introduction
01 Material Families
02 Catalogue of Materials
03 Processes
& Think Different
Index
Credits

Citation preview

00 materiology the creatives guide to Materials and Technologies by matÉrio Authors: Daniel Kula and Élodie Ternaux Associated author: Quentin Hirsinger Graphic designers: Général design, Maroussia Jannelle with Benjamin Gomez Publishers: Frame Publishers amsterdam and Birkhäuser Basel

CONTENTS

Introduction p.7

01 FAMILIES OF MATERIALS

p.9

This first chapter explores 11 familiar families of materials, including wood, metal and plastic. Following a short introductory text, the future of each family is discussed alongside a detailed analysis of their physical, chemical and technical properties.

02 CATALOGUE OF MATERIALS

p.117

A catalogue of 127 ‘every day’ materials, presented as index cards and arranged in alphabetic order. Each card includes a picture, a description, the classical uses and points out the advantages and disadvantages of the material.

03 PROCESSES

p.255

How to deal with materials? The major techniques for processing and adapting materials are described.

& THINK DIFFERENT

p.335

As well as feeling, evaluating and processing materials, you can also reflect on them. This last part gathers a series of theoretical articles placing materials and technologies into historical, economical, social and political perspectives. The main debates within the field are covered and lead us to present issues which will, without a doubt, influence the role of tomorrow’s materials.

INDEX p.367 / Credits p.375

Pleasure and frustration have both pervaded the writing of this book. The simple pleasure of a material and contact with it, the desire to understand it and, above all, to consider it as a great way to set about creating designs and sharing ideas. To enter this world, the recurrent frustration of generally finding tomes of forbidding complexity, which require substantial background knowledge and are too often inaccessible to the non-specialist, frequently leading them to abandon their search. This book is therefore intended for all young, or not so young, creators – designers, architects, artists – who do not, on the face of it, have a vocation as technicians but who will on the other hand need to talk to them. The objective is not to aim at specialists – who will very likely find approximations or omissions – but to go some way to stirring curiosity and interest, to bring a first level of understanding of materials and fabrication techniques, to offer aids to making straightforward choices, which will eventually lead to searching in more specialised works. Deciding on the level of information to include is always very difficult and subject to caution. On our part, it was, from the outset, guided by a desire not to overburden, to go for the essentials, maintaining a flow and making it an easy read. We give a general view, which allows a dip into the book without losing the overall perspective. Above all, we bring together, in one manual, all the materials and major working techniques, to make a search for information direct and practical. The book is organised in four distinct parts: the major families of materials (concrete, wood, composites, leather and skin, light, metal, paper and cardboard, stone, plastics, textiles and glass and ceramics) are studied first; then a catalogue of more than a hundred index cards quickly allows you to find the key elements of materials in our daily life, from cardboard and plywood to copper, polystyrene, incandescent light sources or safety glass; the major techniques for processing or conversion of the material are then described: assembly methods, cutting, stamping or injection; finally, some items for reflection, allowing the reader to put questions of materials and technologies into a wider context. Special attention has been given to the quality of the illustrations which, for us, constitute an intu­itive and effective means of explanation, limiting the need for tedious explanation. The book can be read straight through, in the normal way, but the arrangement of the book also invites the reader to dip in anywhere. At the end of each of the major families of materials there is a system of cross reference to the material catalogue and the processing or conversion techniques linked to the family. This encourages the reader to go in and out, here and there and if possible, to penetrate this detailed universe of materials and technologies, where everything exists and evolves in a perpetually intertwined manner.

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01 material families

WOOD p.10 / PAPER, CARDBOARD p.24 / LEATHER, HIDE p.32 / METAL p.40 / GLASS, CERAMICS p.52 / PLASTICS p.64 / COMPOSITES p.72 / TEXTILES p.82 / STONE p.90 / CONCRETE p.98 / LIGHT p.106.

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Wood Wood: a material that grows Unique in its ability to self-propagate under our very eyes, with ever reassuring familiarity, wood sets itself apart from other materials that often require human intervention to make them suitable for use. Spread over more than a third of our planet, with hundreds of species co-existing on it (broad-leaved trees [angiosperms] and coniferous trees [gymnosperms]), forests – subject to changing climates and soil types – provide today’s designers with a range of fine domestic woods and countless imported species. Amongst one of the oldest construction materials, wood never actually played a leading role in the industrial revolution. Ironically, its inability to guarantee the uniformity, reproducibility and accuracy that industry demands – which could have seen it disappear from the market – have proven to be its strengths, helping to carve a niche market with a refreshing appeal in our modern age. Primarily and quite simply because history and advances in technology do not prevent trees from growing. During this era of sustainability, wood is able to claim a truly competitive ecological advantage, non-chemical treatments recently perfected ensuring it is fully recyclable. As a natural composite material, an organised set of bio-polymers, wood is lightweight yet by comparison extremely advanced. Admittedly, steel, for example, is ten times stronger than high-quality spruce but it is also twenty times heavier. The anisotropy of the wood (different behaviour depending on the effective orientation of the material), a quality which hindered its industrialisation, has now been highlighted as a definite advantage reflected in the increased demand for composite, honeycomb and other resin-reinforced materials. In a modern world that is far from perfect, wood remains the material that is available, immediate, obvious. It is the poor man’s material: accessible, taken for granted, ready for gathering. The real survival material, it warms, helps to build and is interchangeable: the all-consuming exploitation of the Amazonian jungle bears witness to this. Reigning supreme, wood is irreplaceable for a number of applications, with advances in the field slow but worthy of note. Other than solid timber, which can now be heat treated at the core by the process of retification – the chemical pollution from components used up to now being eradicated – the world of wood broadly opens to all of its derivatives, some of which are extremely refined. The line of products incorporates carefully designed timber products such as OSB (Oriented Strand Board), heat treatments to achieve pliable wood (that can be worked like leather or even fabric), air foam wood, plywoods that can be creatively moulded in three dimensions, right through to wood polymers, ‘liquid’ woods, which mix wood waste and plastic resins that can be extruded or injected. If wood has not followed in the footsteps of competing materials and is not caught up in the unbridled onset of thundering innovation, it serves as a perennial reminder to us that no mat­erial is ever intrinsically obsolete and continues, unassumingly, to grow under the watch of Robin (w)hood!

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silhouettes of A variety of tree species within the broad-leaved tree family: 1 acacia 2 maple 3 bird’s eye maple 4 Oregon alder 5 birch 6 Australian or she oak 7 pecan 8 box 9 sweet chestnut 10 black bean 11 Ceylon lemon 12 violet wood (Jacaranda – Dalbergia genus) 13 cocobolo (Dalbergia retusa) 14 Ceylon Ebony (Diospyros ebenum) 15 jelutong (Dyera costulata) 16 walnut

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silhouettes of A variety of tree species within the coniferous tree family: 1 European silver fir 2 kaori tree (New Zealand) 3 Panama pine 4 Australian pine 5 cedar of

Lebanon 6 cypress 7 rimu (or red pine) 8 European larch 9 European spruce 10 Sitka spruce 11 Californian sugar pine 12 plum-fruited yew 13 Ponderosa pine 14 Weymouth pine 15 Scots pine 16 Oregon pine 17 sequoia 18 silver pine 19 cedar 20 Californian hemlock

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FORESTS Today man is connected with the forest by three links: The social: Careful stewardship of one of the final landscapes to offer city dwellers adventure, leisure, mystery, exploration, history and the imaginary, for man, the forest is a space in which to come face to face with nature. It is part of landscape planning, shap­ ing the contours and the natural environment. • The ecological: The true ‘global air conditioning unit’, a machine for ‘recycling’ CO2 by photosynthesis (1.6 tonnes per tonne of wood), a machine for producing oxygen, the forest plays an essential role in the equilibrium of our planet. Uncertainty arises from the current imbalance. We are actually producing more CO2 today than the plants are able to absorb – this leads to greenhouse effect. The consequences of large-scale deforestation – as in the Amazonian jungle – can be felt far and wide. Deforestation is responsible for approximately 20% of the world’s emissions of greenhouse gases, which contribute to global warming and the decline of a number of endangered species. • The raw material: The forest provides us with ‘wood’ as a raw material, a material that has the special qual­ ity of being renewable (renewable in the short term compared with fossil fuels) and recyclable. The transformation and processing of wood consumes little energy and in some cases is self-sufficient. Wood is, potentially, as much a material as a fuel source. Our forests represent an enormous repository of raw materials. Throughout our planet, they take up roughly 30% of the earth’s land surface (4.1 billion out of 12.7 billion hectares of land surface area). If the distribution of the forest is not completely uniform between all countries, varying between 1% and 98% of a country (in the case of Guyana, for example), forested areas are actually distributed relatively equally between the North and the South of the planet. The large clumps of forested area include: ex-USSR and North America, which rep­ resent 40% of the forested land mass, followed by the Amazon and Africa. •

The uncontrolled exploitation of forested areas – long considered to be an inexhaustible repository of materials – has in history led to very serious and hazard­ous imbalances (the near complete disappearance of the English forest in the nineteenth century, when wood was widely used as fuel in the manufacture of steel). The well-ordered management of our woodland herit­ age has given rise to the development of controls other­ wise referred to as silviculture. The purpose of these controls is to regenerate the forested areas which exist and to artificially create new ones, making it possible to achieve ecosystems that can be exploited in rela­ tively short periods of time and can be maintained in

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a state of equilibrium. Silviculture plants, selects, adds and replaces, permanently maintains and manages the extremely sophisticated and subtle balances of the for­ est, detects parasites and diseases and is continually intervening to safeguard the healthy condition of the forested land mass until it is ready to be exploited. Such exploitation starts with felling often­completed by humans and very heavy mechanical tools.­Exploit­ation of the forests is a veritable industry. France, for example, employes more people in that sector than in the automotive industry. In 2000, global employment amount­ed to 13 million people. The total volume for worldwide annual production of timber is around 3.4 billion m3. Half of this production is consumed in the form of firewood (in developing countries amongst others, where this may represent up to 80% of the volumes being exploited).

 10

To differing degrees, more than 1.6 billion people extract their means of existence from the forest, from medicinal plants and food, to removing it for firewood.

TREES Wood is a natural material, which provides an extensive range of species and grades. There are several thousand different species in the natural environment. In the West, more than about a hundred species are currently commercially available. Choice is determined by mechanical properties, density or durability and by aesthetic properties, which within a species can vary depending on the place of origin or the tree itself. As a result, when working with solid timber, pieces have to be carefully selected (gen­erally, professionals buy a batch of complete logs – complete trunks – to guarantee a certain degree of uniformity in production). A distinction must be made between two large families, broad-leaved trees and coniferous trees: • In the case of coniferous trees (gymnosperms), you will find approximately 400 species which essential­ ly come from the northern hemisphere (Canada, the Black Forest, Nordic Countries, the west of France). These are evergreen trees that are fast-growing (on average 60 to 80 years). They are essentially used for construction and structural framework. • In the case of broad-leaved trees (angiosperms), you will find several thousands of species, which essentially come from temperate and tropical forests (Africa, South America, central France). These are decid­ uous trees that are slow-growing (on average 120 to 200 years). They are essentially used for furniture.

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 2 cross-section (end grain)

tangential section (wood grain)

radial section (wood grain)

bark cambium annual growth ring rays pith heartwood sapwood

TREE TRUNK SECTION

 4

crown 3

 

top log

annual growth ring

trunk

log

base root

summer wood

spring wood

MICROSCOPIC TRANSVERSE SECTION OF A SOFTWOOD

FELLING AND PROCESSING

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Wood is also classified as hardwood (often broadleaved trees) or softwood (often coniferous trees) and can also be broken down into three categories, accord­ing to their density: lightweight wood (from 0.4 to 0.8, usually softwood), semi-heavyweight or heavyweight (in excess of 1, usually hardwood).

 2

A tree grows externally each year adding a layer to its periphery: the annual growth ring. The cross-section of a tree will reveal its history. You can distinguish, particularly in climates with distinct seasons, between spring wood and summer wood – a light layer as opposed to a dark layer. Only perfect wood (heartwood) – wood that has reached maturity – is used in the commercial exploitation of wood. Sapwood is eliminated. It is wood that is ‘too young’, saturated with all of the tree’s nutrients, which usually neither has the colour nor the properties of the heart­wood and which quickly decomposes and also represents an attractive home to parasites. Some sapwoods, however, are not ‘characteristic’ and cannot be distinguished from heartwood. The thickness of sapwoods also varies greatly according to the species. The inner bark – or liber, which transports the processed sap (descending), is no longer used; nor is the bark nor the heart centre (often weak, very irregular and vulnerable to insects and fungi). However, nothing goes to waste from the tree. Anything that is not destined for the saw mill will be used for firewood or for pulpwood, for (paper) pulp and some fibreboards and chipboards.

MICROBIOLOGY

 3

Wood is a composite organic and natural material, a sophistication that man rarely achieves when applying himself to manufacture composite materials. Its microscopic structure reveals this. Mainly made up of three polymers (that is, ‘plastic’ materials), wood derives its unique prop­ erties from an intelligent layout of the cellulose, hemicellulose and lignin, in the approximate ratio of 50/25/25, depending on the species and biological variations: • The cellulose: Common to all plant species, is the source of the fibrous structure of wood cells and pro­ vides it with its strength and rigidity. It can be found as a basic constituent of paper, plant textile fibres and even some foods. • Hemicellulose: Surrounds it. Absorbent and able to swell, hemicellulose is otherwise responsible for the dimensional variations of wood. • Lignin: Acts as a cement between the fibres of the wood and as a stiffening agent inside the fibres. Acting as a thermoplastic polymer, it is this amongst other things that will allow deformation of the wood by stoving.

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Different species of wood also contain numerous ex­­­­ -t­reme­­ly useful substances, like resins such as turpentine and pine oil, tannins (in heartwood or in bark), rubber (in inner bark in the form of latex) and cedar oil or maple sugar. These organic materials combine to form different plant tissues: • A fibre bundle: oriented axially, is the main configuration that determines the direction of the wood, or its ‘grain’. The fibres also run radially. • Vascular tissue: which allows the unrefined sap to be transported from the roots to the leaves (through the sapwood). • Spare cells (wood parenchyma). The arrangement of the tissue, the size and the shape of the cells are characteristics of each species. Wood, as it is used by all, is in fact the ‘dead’ part of the tree, the part where the sap no longer circulates. Given the physico-chemical complexity of wood, each part of wood has a behaviour significantly different to others, which explains the difficulties encountered in its industrial production. This sophisticated layout is also the source of the wood’s anisotropy – a quality or defect? In fact, wood does not demonstrate identical characteristics accord­ing to its respective grain or direction. In each direction, shrink­age, mechanical and aesthetic properties can vary extensively. A distinction is made between flat-grained wood, cross-grained wood and end-grained wood. The way in which wood is milled is therefore a critical factor.

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Cutting In a tree, the commercially exploitable part of the joinery timber is relatively limited. It comes down to the flitch, (log) the most rectilinear and uniform part of the trunk. This inevitably determines the final dimensions of the sections of wood that will be made from it. There is no way of obtaining a plank three metres in length if the tree only measures two. Depending on the species, the foot (stump) and the second log (fork or crutch) can provide sections with surprising aesthetics, such as the burr, a wood that is leafy and twisting. Otherwise, they will be used, in the same way as the branches, as pulpwood. Milling a trunk causes the internal tensions to be released that were hitherto ‘locked away’. The behaviour and the quality of each piece of wood is dependant on the chosen method of conversion.

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CLASSIC WOOD CUTTING METHODS

1 flat sawing 2 plain or slash sawing 3 rift sawing 4 quarter sawing

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tangential (major)

transverse (minor)

WOOD SHRINKAGE ALONG THREE AXES OF WOOD

SHRINKAGE AND DEFORMATION ACCORDING TO CUT

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The most popular and economical methods of milling are plain or slash sawing and flat sawing. The quality of the wood is very irregular here but losses are limit­ ed. Rift sawing or quarter sawing, for example, ensure that a more uniform, strong and consistent flat-grained wood is produced. To optimise this process, nowadays milling is complet­ed using sophisticated computer-controlled saws. Different parts are sawn depending on their use: planks (construction); flitches and strips (furniture); joists, slats and studding (structural framework); wall posts (masonry); veneer (by means of fine slicing or rotary cutting – modelled on the ‘pencil sharpener’, for furniture, packaging)

SHRINKAGE

generally, to be used outside, it needs to be treated. To make things even easier, each species will of course have its own unique behaviour in terms of these treatments. They can be applied as a preventive or curative measure. Preventive treatments are basically applied: • either by dip coating (dipping the wood in a bath) • or by impregnation (wood placed in an autoclave and pressurised) Curative treatments are applied: • either by a paint-on treatment (brush-on or with a roller) • or by spray (spray gun, air sprayer) • or by injection (using types of syringe) There are four major types of treatment: Insecticide treatments: To protect against insects. Two to three hundred species of insects throughout the world are responsible for extensive damage to all types of wood: dry wood, hardwood, softwood, inside the sapwood, heartwood and even paper. Amongst the most formidable are: the house longhorn beetle, which is able to reduce a joist to sawdust within 10 years; death watch beetles, which also effectively eat away at floors and cupboards; termites, a veritable curse in the tropics, which are even present in urban environments. • Fungicidal treatments: To protect against fungi. If wood retains more than 22% water, rotting processes take hold. The growth of fungi occurs intensively between 25°C and 35°C. Interior and residential work can suffer the attacks of trametes and polyporus, for example, but the most formidable remains dry rot, otherwise called ‘house fungus’. It causes so-called ‘cubic’, dry, red rot and reduces wood so that it is similar to semicarbonised wood. At the outset it manifests itself in the form of thick, white cotton wool. There is a wide range of ready-to-use, commercially available products for treating these pests, phenol-, chlorine-, fluorine-, creosote-, copper-based. • Dampproofing treatments: To protect against damp. In order to guarantee the highest possible degree of dimensional stability and also to avoid rot, the wood is soaked by means of dipping or injection, with resin, which saturates the wood and is able to go as far as to remove any reaction causing shrinkage or swelling. There is currently a heat treatment called retification, an ecological alternative to the purely chemical, pollut­ing treatments. In an inert atmosphere, at more than 200°C, wood is heated to create a material with improved dimensional stability and durability. A slight brown colour­ation and a minor reduction in its mechanical properties are, however, side-effects of this procedure. • Fire-proofing treatments: To protect against fire. Wood is a combustible material and everyone knows that fire can be made with wood. Paradoxically, wood •

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Wood is constantly shrinking, particularly whilst drying and sections of wood will have a tendency to deform unevenly depending on the three directions in space. Well managed conversion will succeed in minimising the consequences of shrinkage.

DEFECTS  8

Wood may present a number of defects, some directly linked to the phenomenon of shrinkage such as curl­ing, warping and splitting. Knots, frost cracking, ingrown bark are amongst the many irregularities that make this material difficult to work with.

DRYING A tree is saturated with water, sometimes up to 200%, according to the species and the ambient moisture levels. Controlling the degree of moisture is therefore essential for the commercial exploitation of the wood. In fact, wood (ready for processing, sawn up or made into a chair) is constantly behaving like a sponge: upon drying out, it shrinks, when wet, it swells. Drying therefore consists of removing the water content in the wood in order to best stabilise its behaviour. There are two types of drying: natural (in the air, for several months or several years) and artificial (by stoving or in a kiln, for a few days). Commercially, wood is deemed to be dry when it has a degree of moisture that is between 18 and 22%.

TREATMENTS Wood, depending on the species, will have varying durability. It can be used without special treatment but

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DEFECTS IN WOOD 1 curling 2 bending 3 knot 4 crack 5 warping

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PRODUCTION OF VENEER 1 rotary cutting (continuous) 2 slicing (sheet by sheet)

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can effectively counter the effects of fire. It does not deform, it does not release toxic gas, it burns slowly, allowing the necessary time for an evacuation of any people. Its behaviour is predictable. International classifications are in place but, even today, each country has its own standards. Wood and its derivatives can be fire-proofed, allowing it to be granted, in terms of fire performance, the classifications ‘average flammability’ (M3 in France, D for the European standard) to ‘inflammable’ (M1 in France, B for the European standard). This fireproofing process can be superficial by applying coatings or even paints or a barrier-type or intumescent-type varnish. It can be mass-produced by injecting fireproof saline solutions, which is effective but is unfortunately also polluting. The valid service life of fireproofing treatment is limit­ ed in time (between 3 and 10 years depending on the treatments). Fire resistance defines the time during which construc­ tion elements can play the role for which they are intend­ ed in spite of the effect of a fire. There are 4 criteria to take into account: • Mechanical resistance • Flame retardancy • The absence of flammable gas emissions from the exposed surface area • Heat insulation Fire-stable elements are those in respect of which only the first criterion is a requirement; flame-resistant elements are those in respect of which the first three criteria are required; fire-rated elements are those in respect of which all of the criteria are required.

SOLID WOOD / WOOD DERIVATIVES From an industrial perspective, wood is in fact a material whose faults limit its intensive exploitation. That is why the nineteenth century, taking advantage of mech­ anisation, developments in chemistry and the arrival of high-performance adhesives and plastic materials, saw the emergence of a new category of materials, wood derivatives. These allow wood to be adapted to industrial requirements to create a reproducible, reliable and uniform material. Wood derivatives minimise the chronic faults of solid wood: less dimensional limitations, less shrinkage, better surface evenness, less susceptibility to splitting. The arrival of wood derivatives has turned the design of furniture upside-down. Where carcases used to be manufactured and then finished with panels, they are now finished with actual single, contiguous boxes. An entire range of adapted hardware has also been de-

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veloped from derivatives: specific screw fittings and assemblies, inserts and invisibles hinges. If wood derivatives optimise certain qualities of solid wood, each type of derivative still has its advantages and disadvantages (See part 02). Wood derivatives are currently grouped under the classification of EWP (Engineered Wood Products).

PROCESSING Wood is without doubt the most commonly used material for doing ‘odd jobs’, firmly rooted in tradition and common practice. Alive and kicking handicraft woodwork has promoted the development of a whole range of small, portable electric tools, from ‘amateur enthusiast’ to professional in quality, allowing anyone to work on location and directly on building sites. Bordering on outlandish, there is now a tool for every operation. This overspecialisation does, however, contribute to making working with wood something that is familiar and accessible. DIY enthusiasts, equipped with all the attributes of professionals (but to a lower standard) are more and more prolific. On the other hand, the gap widens between heavy industry, equipped with highperformance machinery, computer-controlled, etc. and craftsmen with lightweight equipment. The method of manufacturing wooden objects has evolved greatly. ‘Made entirely of wood’ is a rare thing: wood-metal and wood-plastic combinations are emerging. The compatibility between wood and these various materials does sometimes raise some concerns. The appearance of kit furniture and structural frame­ work has also greatly simplified the process of making things with wood.

WOOD AND INNOVATION Given that man has had a relationship with wood as a material for centuries and has not seen it changing, developments in this field are discrete but without any doubt tangible. As opposed to the creation of new species, innovation focuses on tools, on the transition to computerisation and robotics and on the development of increasingly high-performance derivative wood prod­ ucts. At a time when special attention is being paid to the environment, wood as a material is attracting renewed interest. Retification of wood makes it possible to provide, for example, a treatment that does not involve the introduction of toxic products, allowing clean recycling of the material.

 10 paper and cardboard consumption (0,23 Gm3)

consumption for wood-based panels (0,13 Gm3)

wood used as an energy source (1,8 Gm3)

sawn-wood consumption (1 Gm3) consumption for paper pulp (0,4 Gm3)

other consumption (0,2 Gm3)

industrial round wood (1,6 Gm3)

world production of round timber (3,4 Gm3)

BREAKDOWN OF CONSUMPTION AMONG WOOD INDUSTRIES

(1 Gm3 = 1 billion m3)

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We are also witnessing a veritable elaboration of known principles, such as combinations of PMMA/ Wood, reconstituted veneers. Wood as a material, ‘pushed to the limits’ is capable of producing: flexible wood, the product of ultra-high compression and stoving of end grain, actual wood­ en ‘wallpapers’, three-dimensional plywoods, obtain­ ed by fragmenting veneer sheets, ‘wood-plastics’ or ‘wood-polymers’, which can be injected or extruded using wood shavings (sawdust, powder) or pulpwood in thermoplastic matrices. Further research and development propositions contin­ ue to emerge, with products like wood foam – manufactured from sawdust, stoved like a traditional loaf of bread and wood welding – discovered by chance after forgetting the adhesive in a friction adhesion test.

List of materials examined in part 02: Bamboo p.131 /

Chipboard

Laminates

p.175 /

p.139 /

Veneer

Wood species

p.144 /

p.243 /

p.199 /

p.126

/ Burrs

Laminated timber, glued

Lathboard or coreboard

ed-strand board (Osb) p.209 /

Cork

Plywood

Wood polymers

p.177 /

p.208 /

p.244 /

Mdf

p.191 /

p.174 /

Orient-

Plywood, moulded

Wood, retified

p.245 /

p.246.

List of processes examined in part 03: Assembly p.272 / Bonding p.278 / Cutting p.260 / Digital processes p.316 / Finishes p.324 / Machining p.268 / Printing p.320 / Resin moulding p.300.

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Paper, cardboard PAPERS PLEASE... Up to very recently, no other material will have better captured man’s language and memory than paper. And yet, from a precious and essential material, paper has simply become banal. So readily available that it is almost overlooked. Lightweight, accessible, the obvious choice, humdrum. Serving a society in which the throw-away reigns supreme, it has started to develop into an object in itself, available for a large number of applications: packaging (the vehicle for brand identity, which in some countries is bordering on an art form or a cult object), hygiene, filtration and architecture. With annual global production reaching 400 million tonnes at the start of the twenty-first century, largely due to the United States and areas where Asians remain large-scale manufacturers (China and Japan), the consumption of paper per inhabitant is indexed according to each countries gross national product. Producing revealing statistics. Like regional culinary specialities, there are many different recipes, methods of preparation and consequently styles of paper. The fibres, which form its structure, are not limited to those extracted from wood (where diversity, with all its differences, is still the dominant factor) but also come from recycled paper, from rags or plants such as cotton, linen (flax), bamboo or algae. The non-industrial or industrial production of paper pulp and then paper web leaves its mark. A very wide range of papers and cardboards are now available, by freely varying the bulk, the hand, the formation or the format of the material. The paper industry has in fact only recently been mechanised and yet the craftsman’s knowhow still endures. The pleasure of fine papers is shared by art editors, collectors, artists, designers. Despite being considered a relatively natural material, the organised production of the material is not without environmental impact and the paper and board industry still have some way to go to meet the increasingly stringent environmental requirements. Even recycling, which plays a vital if not central role in some countries, has recourse to use some disputed chemical products. This represents one of the great challenges in this field. However, by nature, paper opens the door to a lighter, more ephemeral, three-dimensional world. The tradition of Origami and the cardboard structures made by Shigeru Ban are testimony of this. These structures are constructed quickly and easily, inexpensive and less greedy in terms of materials than classical architecture. Its indisputable qualities of strength compared to its weight, amongst other things, allow paper to proudly sit alongside the materials of tomorrow, to be used for untold applications. Until last century paper was virtually the only aidemémoire. Today, however, such supremacy is fierce­ly contested by electronic memory. Books are digitised and information technology has taken over. Will the electronic medium be as reliable or more reliable, in time, than paper? There is every chance that the two will endure and combine in some way: paper has not written its last word.

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HISTORY Originating from Egyptian papyrus (which sealed the fate of paper, starting with its very name), the invention of paper goes back to the dawn of time. Replacing the traditional rolls of reeds, Asian parchment was intro­duced – a material of animal origin, fine (vellum – based on the skin of stillborn calves – is the finest) used on both sides. Fragments of parchment, placed together were used to create a codex. Paper, as we still make it today, is of Chinese origin, perfected around the 2nd century, from old rags and vegetable fibres – such as hemp – masticated, sieved then dried. Forced to share their recipe in the eighth century by the Arabs in Samarkand, the knowledge of the paper makers was exported, triggering large-scale manufacture. Thanks to, amongst other things the invention of the printing press by Gutenberg in 1445, production spread from the Middle East to Spain and then throughout Europe. The Industrialisation of the manufacture of paper is only a recent development given its long existence. In fact, the first machines able to complete all of the stages of its manufacture – from pulp to paper web – only appeared in the eighteenth century. From the 19th century paper has been manufactured from wood – an alternative to rags which were in short supply.

COMPOSITION It is cellulose – the basic component of fibres – which governs the existence of paper (like that of textiles, in fact.) A piece of paper mainly consists of fibres (up to 95%), the remainder of its composition is then made up of glues or various bonding agents and pigments. For 90% to 95% of paper today, the cellulose comes from wood. Different species of trees produce fibres, which make it possible to structure paper as a material – long fibres from softwoods, short ones from hardwoods. When the fibres do not originate from wood, they can be obtained by reprocessing rags, amongst other things. This method was used for a long time; and continues today amongst some craftsmen. Long, uniform cotton fibres and flax fibres make it possible to produce high-quality paper, solid, resistant to the on­slaught of time and aesthetically pleasing. Jute, ramie, nettle and mulberry fibres can be used, as well as algae. The fibres of different plants, such as bamboos in Asia, kenaf in the tropical countries, sugar cane (particularly sugar cane bagasse, a by-product from the commercial exploitation of sugar), cereal straw (wheat, rice, rye) are also used. Mineral fibres (glass, amongst other things) and plastics sometimes (in fact increasingly) find their way into

26

the composition of paper. These make it possible to further enhance its qualities of resistance to folding, ripping, water, amongst others, as well as its behaviour over time, which are useful in some applications.

PAPER PULP In order to manufacture paper, you start by making paper pulp, which is full of fibres and then this pulp is converted into webs. There are three distinct methods of obtaining pulp: mechanically, chemically or by means of recycling. We talk about obtaining ‘virgin pulp’ in the case of the first two and ‘recycled pulp’ in the case of the third. Mechanical procedure: Wood, converted into billets and chips, is mechanically defibrated (pulped) through the action of abrasive grinding wheels combined with water and heat. This coarse mechanical defibration or pulping produces pulp, the so-called ‘pulpwood’, with cut fibres and still with a high lignin content (see Wood p.10). With this pulp, you will obtain opaque paper offer­ ing poor durability, which quickly yellows. This paper will be mainly used for newspapers, magazines and the inside of cardboard. • Chemical procedure: Wood, after it has been converted or shredded into small chips, is put into a ‘digester’ where it is baked for several hours at high temperatures (130°C to 180°C) with a chemical curing agent. This type of process makes it possible to obtain a pulp, a so-called ‘non-wood pulp’, with fibres that are less damaged, widely used in America, Sweden and Finland. It is a process offering a lower yield than the mechanical process. The curing agent used is either alkaline, or acidic. With an alkaline curing agent, we refer to the Kraft process (a name with which you are likely to be familiar) from the German and Swedish word meaning ‘force, strength or power’. The pulp that is obtained is a brown or grey pulp, offering a high level of mechanical strength and which can be directly used to manufacture packaging. With an acidic curing agent, the pulp will not be as strong as a mechanical pulp, but it will be more flexible than an alkaline pulp. It will be used to manufacture high-quality writing paper. These two types of treatment have the same disadvantage: the chemical pollution that they cause. Gas­ eous toxic emissions or the disposal of chemical solutions from the digesters are now prohibited. • Recycling: In this case, the pulp is obtained from paper and cardboard, which have already been used. The recycled fibres come from a variety of recycling methods. At an industrial level, it is possible to collect the off-cuts at printing works, packaging, unsold newspapers and magazines and at a domestic level, packaging and •

 1

paper. This source of raw materials is far from being negligible. Today, the share of recycling in the manufacture of paper is as much as 60% in some countries, transforming the paper-making industries into real re­ cycling industries. To obtain pulp from recycled objects, the recycled paper is moistened and stirred. After this it is washed to get rid of glues or inks and to remove unwanted components, such as staples (extracted by magnetisation), certain pieces of plastic, etc. Generally speaking, fibres recovered by recycling will be used in the manufacture of packaging paper. Regardless of the method used to obtain the paper pulp, if it is not really white, it will require bleaching. A purely aesthetic process, which optimises the paper’s qualities of resistance to breaking and weathering. The paper’s level of whiteness is measured in ISO. 100% being the maximum value. The ISO number corresponds to the whiteness of magnesium oxide – the whitest material that we know – which reflects 100% of the light. Once the pulp has been bleached, it will have degrees of whiteness, which generally vary from 70% to 93% ISO. Different bleaching processes are available depending on the (mechanical, chemical) pulp. Hydrogen perox­ ide, chlorine, ozone, oxygen are some of the bleaching agents currently used. It is important to remember that this stage of manufacturing paper is particularly expensive and fairly polluting. Once bleached, the pulp is then refined. The fibres are dipped in water and subjected to mechanical processes to reinforce their structure and to increase contact surfaces. Following the refining process, the pulp is then able to receive additives. Mineral fillers such as Chinese clay, talc, chalk, etc. improve opacity, the glazing of webs and printability. Bonding agents, such as rosin or starch promote improved internal cohesion. Gelatine enhances resistance to solvents. Fungicidal and antibacterial agents inhibit deterioration of the paper and colorants, of course, produce coloured paper. Once all these stages have been completed, the pulp, finally ready, will either be directly transformed into a web in integrated factories, controlling the complete manufacture of paper from start to finish, or dried and compacted to be transported to become paper webs.

The wet stage: The diluted pulp (between 1% and 3% dry matter, the remainder water) is fed into the machine and, similar to the process of plastic extrusion, exits via a crack and runs off along the width of a conveyor belt (a taught metal wire, which can be up to 10-m wide and more than 100-m long.) At this stage, the water immediately starts to drain off. A fibrous mat is formed with a non-uniform distribution of fibres – thick and long / fine and short. The objective is to enhance cross-linking. This mat, guided by a ‘couch’ felt, will then undergo a press procedure. Water is once again removed and by this stage is only between 30% and 40%. The water collected throughout this process, containing fine, short fibres will be reused in the early stages of the manufacturing process. • The dry stage: Upon leaving the presses, a web is obtained that is able to dispense with the ‘couch’ felt and is ready to be subjected to the successive drying stages. The web is guided between large heating then cooling cylinders, which dry both sides at the same time, removing virtually all of the water (approximately 5% will remain). Paper leaving the drying phase is referred to as ‘bulking paper’, as its surface is still uneven. The final stages of physical preparation, such as glazing and then calendering, still between steel cylinders, crush any imperfections and optimise the thickness of the web and the appearance of its surface. For example, you can obtain paper with a shiny surface by means of calendering. This is referred to as supercalendering. After completing all of these processes, the webs are rolled onto a coil, ready for commercial use or are precut in a variety of formats. •

PAPER TREATMENTS It is often necessary to undertake specific treatments to improve the surface of the paper and its printability. A widespread treatment is that of coating, in which an improved feel, enhanced writing quality, less porosity, more attractive whiteness, etc. is produced. This can be attained by depositing pigments (minerals additives) and binding agents onto one or both sides of the surface. Most paper used for printing or writing is coated paper.

characteristics OF PAPER THE PAPER WEB

While the art of manufacturing pulp consists of separat­ ing the fibres, to obtain webs of paper you need to bring them together. Two main stages precede the manufact­ ure of paper webs: the wet stage and then the dry stage.

The mass per unit area (grammage) This is the mass per unit of surface area, measured in g / m2. This ranges from ultra-lightweight and lightweight paper, such as cigarette paper, which has a mass per unit area of 15 g / m2, to 80 g /m2 traditional writing paper all the way up to high-gsm paper.

27

The hand This is the relationship between the thickness of the paper and its mass per unit area. Paper is referred to as having ‘a good hand’ when its thickness is increased in relation to its mass per unit area. The direction of manufacture The manufacturing process of webs has a tendency to orientate the fibres thereby involving different behaviours depending on the paper’s direction of use. ‘Machine’ direction – more rigid and easy to flex – is different to ‘cross’ direction – less rigid and lending itself better to creasing. The surfaces Upon manufacturing the web of paper, one of the surfaces will be in contact with the conveyor belt (the metal wire) and the other with the ‘couch’ felt. The two surfaces will always retain a visible difference in texture, even if it is subtle. The wire side retains some marks, for example. The grain This is the feel of the surface of the paper, a very personal assessment of its roughness. The formation (look-through) By scrutinising a sheet of paper by looking through it, you can discover its method of manufacture, its structure: faded formation for uniform fibres or cloudy formation for non-uniform fibres. Bulking paper Bulking paper, as we have seen, is unfinished paper leaving the machine. It is also an adjective describing the tactile sensation of thick paper and finally a cat­ egory of unsized, printing paper, with lots of hand and fairly absorbent. The paper used in paperback books, for example. Whiteness Measured in ISO, referred to earlier. A luxurious paper will have a level of whiteness of between 88% and 93% ISO, whereas newspaper paper is around 65% ISO. Gloss A paper will be made shiny due to its specific composition (using additives) and as a result of the calendering process.

 2

Format Paper, depending on its location and method of man­ ufacture, has long since come in different formats. Since the Seventies, in the printing sector in particular, an international AFNOR standard (Association Fran-

28

çaise de Normalisation or French Standardisation Association) has suggested designations ranging from A0 to A5. Depending on the orientation of the format, we also refer to portrait format or as the French say, ‘à la française’, or upright format when the long side of the document is vertical; and to landscape format or as the French say, ‘à l’italienne’, when the large side of the document is horizontal. The watermark During the wet stage of manufacturing a web of paper, a single thread of iron or brass of the desired shape is fastened to the screen. This will leave the mark of its imprint on the paper pulp and the design transferred in this way will remain legible when looking through the sheet. You can find watermarks in banknote or safety paper, amongst other types.

PROCESSING A pair of scissors, a tube of glue, a stapler, a cutting tool, a roll of Sellotape® and the adventure begins. The extraordinary ease of working with paper makes it familiar and obvious for us, although we face a powerful and largely mechanised industry.

PAPER AND INNOVATION For the paper-making industry today, one of the great­ est challenges is to stop pollution or at least to minimise its environmental impact. Similar to other sectors, environmental issues are highlighting the need for recycling. As a result the proportion of recycling in the production of paper is increasing. The collection and sorting of used paper is organised in numerous countries, with education about how to reduce packaging and waste products being provided. Dare we dream of closed-cycle production? In addition to wood, alternative fibre sources, are emerg­ ing. As previously stated, pineapple or other fruit pulp, bamboo or hemp can be made into paper, as well as algae, for example, those endemic to the lagoon of Venice and whose harvest had no future other than incineration. Every day new paper or cardboard products are appear­ ing. With the exclusion of ‘creative’ paper, which never ceases to surprise and incorporate new visual experi­ ences (paper with pigments changing in colour; with surface treatments providing the feel of suede or of wetness, powerful deep colours; different surfaces, etc.), paper and cardboard might assume a honeycomb structure,

 1

1

7

6

2

5

4

3

8 11

9

10

PAPER MANUFACTURE 1 debarking 2 chipping 3 washing equipment 4 purification and washing 5 whitening 6 pulp tank 7 cleaning tank 8 pulp 9 pressing 10 drying 11 reel winder

 2 paper for graphic and stationery use (50 %)

1 2

various (4 %)

packaging (40 %)

hygiene paper (6 %)

STANDARD PAPER FORMATS 1 landscape 2 portrait

BREAKDOWN OF PAPER PRODUCTION

29

for example. Constituting the core of laminated materials, they offer properties of lightness and compressive strength for door panels, counters or other furniture components. There are also recycled paper-based (Japanese) foams, replac­ing expanded polystyrene in packaging applications, amongst other things. Papers and plastics enjoy quite an intimate friendship. Indeed, paper can be found in the injection of thermoplastics: here it plays a filler role but it is also possible to find paper whose composition is verging on that of a pure polymer. It is used for unrippable, impermeable, resistant paper… which is still printable, fine and creasable. They are made into Tyvek® envelopes, work boiler suits, bank notes, identity documents, etc. Watermarks, as we have seen, remain a much appreci­ ated mark and security feature (proof of authenticity). In terms of security, inks also play their part. Permanently inseparable from paper, they can now only react to ultra­ violet light and can therefore only be detected under special conditions (once again, the ability to check the authenticity of a document). Inks offer some intriguing visual effects. There are raised or puff inks, to provide an embossed effect to your writing, phosphorescent or fluorescent inks, temperature-sensitive, invisible UVreactive inks. The choice is extensive. Printing techniques are also developing and the speed of production, ease of processing and cost are enhanced. Finally, the word paper has infiltrated the field of electronics and information technology to describe thin, flexible and multi-functional substrates. Some papers with a printed pattern communicate with ‘intelligent’ pens, able to transcribe your scribbles to computerised message boards. We talk about ‘electronic paper’ to describe book screen surfaces of tomorrow, or even ‘luminous paper’ when referring to films, silkscreen printed with electroluminescent ink (see Electroluminescence p.147). If you take a step back from cellulose, in terms of its composition, the idea is there: one of the substrate, the medium for information and memory, the notion of an expressive surface, whatever it might be: vertigo (or anxiety?) of the white page.

List of materials examined in part 02: Cardboard p.133 / Honeycomb p.170 / Paper p.200 / Parchment p.202. List of processes examined in part 03: Assembly p.316

/ Finishes p.324 / Folding p.264 / Machining p.268 / Printing p.320

/ Cutting

/ Sewing p.288 / Stamping p.290.

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p.260

/ Bon-

ding

/ Calendering

p.302

p.272

p.278

/ Digital processes

Leather, hide BETWEEN LEATHER AND FLESH An object of desire, a mark of luxury, with connotations of the illicit, adventure and sometimes decadence, leathers and furs, second skins, create an air of ambiguity. Leathers continue to fascinate, veritable hunting trophies, awakening man’s animal instincts, separated from the animal, changing hands to the highest bidder, even finding its way onto the black market, where the desire for the forbidden becomes overwhelming. A material with a unique character – which is what also gives it its value – each dismembered animal will have its own specific characteristics, its own history. Like the close-fitting jacket, the fetish shoe, polished a hundred times, or the tired club armchair, they too bear the mark of their owners’ past. One of the rare materials for which wear and tear is accepted – indeed marketed – vaunting the imprint and ravages of time, leather is a tactile, contact material, with an almost suspicious familiarity: like our skin, it breaths, lives, gives way to many a whim and all the while emits a sensual sweet scent. The opposite of armour and nonetheless, its uses, for clothing amongst other things, never fail to rise to the occasion, to symbolise the inhumanity, the violence and the repression in the clicking of boots or the rustle of full length coats. A vital material questioning the relationship between man and nature. Is leather inexhaustible? For some sought after pieces, sometimes banned (such as the hair coats of some protected animals), it is a rare and precious material. For other more everyday, more accessible pieces, leather can be found in abundance – as the by-product of calf, cow and pig rearing, for example. Worked, tanned, embossed or calendared, the skins become disassociated from the animal. To such an extent we confuse them with imitations. Plastics or textiles can be deceptive and make strong claims on the elevated status of synthetic leathers and furs, even if the substitute is never perfect. Leather remains a truly high-performance material, with its own integral functionality. It is capable of acting like a hinge (like its distant cousin, polypropylene); it is extremely resistant to traction and to expansion; it remains elastic and can be used in combination with traditional methods (special stitching, eyelets, collages). As the only flexible material available to man for a long time, leather became the basis of a great craft tradition, which continues despite industrialisation taking over many of the production processes. Following close on the heels of technological innovation, leather can handle a torrent of treatments, without compromising its intrinsic qualities of breathing and flexibility. It pays heed to the growing concerns for preserving the environment by reducing the amount of water consumed during its manufacture and by modifying the chemical compositions of tannins. However, at the same time, the floodgates to animals, which up until now had been safe in their skins: birds, fish, new species of rabbit created by genetic crossings, amongst others, can now make claim to a place on our handbags or over our shoulders.

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OBTAINING ANIMAL SKINS

COMPOSITION OF THE SKIN

Animal skin is the raw material of a family of well-known materials. Skins that have long since been used; whose work – in the preserved air of the craftsman’s workshop – sometimes borders on the artistic but has also been subject to widespread industrialisation. By nature, skins and hides, like trees, are not subject to the exacting demands of perfection, of reproducibility and dimensions of industry. Everything will depend on the animal’s life, its size, its age…obviously, a delicate industrial process.

Whatever the animal species in question, the composition of the skin can be described as follows: • The epidermis: Essentially made of keratin. • The dermis: This is the part that will become leath­ er. The dermis, the looser or tighter felting of finer or coarser fibres includes the ‘grain side’ and the ‘flesh side’. The sebaceous glands (which secrete sebum), the sweat glands and the hair sheaths can be found implanted within the grain side of the dermis. The hairs are made of keratin whereas the dermis itself is made up of collagen. • The subcutaneous tissue or hypodermis: Made of collagen.

Skins are basically taken from mammals: cattle, sheep, pigs, goats, horses although it is also possible to find the skin of fish, reptiles and birds. The animals, which will be used to manufacture leath­ er, are reared, mainly (with a few exceptions) for their meat, their milk or their wool. The details that follow concentrate on animals for slaughter, which constitute the main source for supplying the leather industry today. The animal’s skin is delicately separated from its carcass – either by hand or mechanically. At this stage, great care has to be taken to avoid causing damage to the skin. It is in fact flexible, with a ‘furry’ side and a side to which strips of flesh, blood and fat are still attached. This skin is called fresh raw skin. It is rich in water and as such will deteriorate very quickly. There are different types of treatment available that can be used to preserve it: • Salting (or curing): Salt will dehydrate the skins, stacked on top of one another for a few weeks. • Brining (or pickling): This form of pickling is completed by submerging the skins into a saturated brine solution. Dehydration takes place over a few days. This procedure is a little more complicated to perform than straightforward salting. • Drying out: When salt is a rare commodity, as it is in some countries, you simply dry out the stretched skin in the fresh air. However, you do need to ensure that drying takes place quickly otherwise the skins will have a tendency to start to rot and decay. • Combined salting and drying. Once treated, the skin is said to be raw skin. It is ready to be shipped off to a tannery or dressing factory. The raw skins are classified into different categories and weights to assist the tanners to make a selection. Thus, sheepskins depend on the length of the wool (a 1/4 wool skin, for example, has wool that is 1 to 2.5 cm long) and the weight of a dozen salted or dried skins. The cow hides are classified according to the bulk mass of fresh raw hide.

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The differences in the composition of the three layers (keratin and collagen) will make it possible to get rid of the epidermis and hairs by means of an alkaline chemical treatment without damaging the dermis. The subcutaneous tissue is removed mechanically.

CHARACTERISTICS OF SKIN As for each family of materials, there is a vocabulary specific to the world of leather to describe skins, their qualities and their imperfections. As we have previously indicated, each skin – or rather each animal – is unique and, there is no identical skin even from the same race or of the same origin. Full or slack skin A skin is referred to as being ‘full’ when the dermal tissue is firm and tight. In contrast, it is referred to as being ‘slack’ when the dermal tissue is loose and soft. These two types can co-exist within the same piece. Round or flat skin A skin is said to be ‘round’ when the central section is thicker than the edges and ‘flat’ when its thickness is uniform. Skin imperfections Numerous imperfections can appear and depreciate its value whether it is during the animal’s life (para­ sites, scars, markings), when the skin is separated from the slaughtered animal (non-symmetrical cut, holes) or whilst being preserved (the start of the aforementioned process of decaying heats the skin, marks due to salting, insects). Structure of the skin Each skin also displays areas that are variable in structure. Depending on the type of animal, the common

 1

 1

hair 1

erector pili muscle sweat gland 4

sebaceous gland

2

5

3

fat cells a cross-SECTION of SKIN 1 epidermis 2 dermis 3 subcutaneous tissue 4 grain 5 flesh

 2

1

2

3

DIFFERENT PARTS OF SKIN (CATTLE, SHEEP, GOAT) 1 top of hide 2 back of hide 3 flank of hide

35

 2

practice is to divide the skins into different sections. In the case of cows, ewes, sheep and goats, for example, a distinction is made between three major areas: • The neck: This corresponds to the animal’s neck area. Often wrinkled, of uneven thickness and looser in structure. It will be difficult to obtain a really smooth leather from this. • The butt: This corresponds to the butt and back section of the animal. This is the fullest part of the skin, of even thickness, with a uniform dermis. The butt will provide the best finished leather. • The sides: These correspond to the animal’s belly. These two sections are uneven in thickness and slack in structure. Big skins are rarely worked on as a whole, in fact there is more of a tendency to remove the sides. Skins that are smaller in size, where any differences become indistinct, are put to maximum use, as you might imagine.

FROM SKIN TO LEATHER Once the skin has been sent to the tanner, three im­p­ ortant stages in its transformation are required to obtain leather: • Wet operation: This first stage helps to prepare the skin for proper tanning. You start by soaking it for a few days in water in order to rehydrate and return the skin to ‘fresh raw skin’. The chemical process of ‘dehairing-lime treatment’ is then undertaken, where hairs and epidermis are removed by simultaneously rubbing or rinsing thereby slightly deteriorating the dermis. This becomes more flexible and helps to prepare it to receive the final treatments. This is slightly different in the case of sheepskins, as it is at this stage that wool is also collected. The skin is then ‘defleshed’ and the subcutaneous tissue is thus mechanically removed. Only the dermis then remains, ready to be tanned after the final stage of ‘deliming’, dur­ ing which the dermis is treated and rinsed over a period of several hours. Almost pure, it is then called ‘pelt’. • Tanning: By starting with a pelt loaded with water, putrescible and almost translucent, this makes it possible to obtain a slightly moist, rot-proof, opaque and flexible leather. The tanning agents – tannins – are responsible for this transformation. Different types of tannins are available, which combined determine the quality of the leather product: vegetable tannins (oak or fir bark, sumach leaves, chestnut wood, fruits or roots); minerals products (chrome, aluminium, iron salts or sulphur) or organic products such as formaldehyde, cod liver oil or synthetic tannins. Chrome salts are the most commonly used and give rise to all types of leather. Mineral tanning of this kind, applied industrially since the start of the twentieth cen­

36

t­ury, is quick. The skins are continuously agitated in a drum (large turning barrel) and are tanned within a few hours. Chrome tanned leather provides excellent mechanical and heat resistance. Vegetable tannins, which are very old, are generally re­­­ s­er­­ved for shoe plate leather, lining and furniture leath­ er. Vegetable tanning consists of moving the leather into successive vats – plumping – with increasingly rich concentrations of tannins and then on to the drum stage. Tanning can take up to about thirty days. Vegetable tanning leathers are less pliable and less elastic and they offer less effective heat resistance. • Dressing-finishing: This final stage (consisting of sev­ eral phases itself) is what makes it possible to obtain the finished leather. However, the leather can already be sold after tanning. In fact you can purchase chrome tanned leather – wet-blue – or vegetable tanned leather, called ‘Rough tanned leather’. The processes of dressing-finishing will vary depending on the type of desired finished leather. Sole leather, shoe upper leather, industrial leather, suede leather, buckskin-type leather, grain embossed leather. So many possibilities and sometimes all from the same piece. Dressing-finishing reverts to mechanical, chemical and drying processes. You start by placing the leather mechanically between felt cylinders, you check and adjust the thickness of the leather by splitting, separating the grain from the flesh split (the flesh side) or by shaving in order to make the thickness even. You then move on to ‘setting out’ where the leather is stretched and made as flat as possible. Chemically, you carry out dyeing (using various color­ants), nourishing (with fatty matter, to provide flexibility and/or watertightness) and some finishing treatments (lacquering or other treatments to improve the properties of the leather and its surface appearance). The finishes are applied by spray gun or by coating rollers and divid­ed into three categories: aniline finish, for a beautiful appearance but delicate maintenance, semianiline finish and pigment finish, for protection against water and stains and offering easier maintenance. Leather is dried in hot-air dryers, in the fresh air or in a vac­uum. Leather can still undergo the processes of beating to increase its firmness or, conversely, of staking, to make it more supple; sleeking, ironing, plating – to perfect the finish of the grain; buffing to obtain suede leather or fi­­n­ally the process of embossing, to create relief imitating rare hides, for example. Following all of these stages, the leathers are classified into different categories. It makes it identifiable by future users that will include shoe manufacturers, leather goods makers, glovers, clothes or furniture manufacturers, etc. Full-grain leather, flesh-split leather, velours leather, buckskin, nubuck, etc. are all names allowing them to be distinguished and chosen.

PROPERTIES OF LEATHER Leather is a high-performance material and its diverse properties provide opportunities and openings in a number of industrial sectors. It has in fact been successful in finding some unexpected applications (the water seal, for example). Its properties however, largely depend on the different types of treatments it undergoes. Leather and water Paradoxically, leather is less damaged by water than sweating. It is a material that is not desirable to have in direct contact with skin, but similarly it is able to ‘breath’ – one of its understated qualities – and absorb moisture. This makes it comfortable to wear in clothes and shoes, for example. Leather and fire The level of flammability of leather greatly depends on its basic nature, its tanning and the various finishes and treatments it undergoes. Nonetheless, leather is essentially fire-resistant. It is after all the blacksmith’s apron. Leather and resistant properties Some types of leather, such as leather intended for furniture, the automotive industry or sports clothing and equipment, display properties of high resistance to traction, tearing, bending, friction and puncture. Leather and temperature As it contains a lot of air, leather is a good thermal insulator. It is generally warm in the winter and cold in the summer. Leather and moulds Leather is extremely resistant to mould. Leather and deformation Leather is a plastic material that is relatively elastic. It can be moulded whilst retaining its shape, for which it generally needs to be moistened.

leather derivatives Real fur is obtained by preserving an animal’s hair (fleece) on its skin. The whole thing will undergo a variety of dressing and finishing processes (shaving, surface dyeing or deep dyeing, printing, embossing, etch print­ed or lace effects, etc.), pretty much exactly like those performed on leather. The fleece, in winter, is made up of two grades of hair: coarse hair (long, solid hair) and ground fur (short, soft hair). In summer, the ground fur disappears, giving the summer skin more of a leather function than a fur function. True fur has real in-

sulating qualities, which made it popular with man very quickly. Today, most fur comes from farmed animals. Various species (mink, fox, rabbit, etc.) are prized for the qual­ity of their coat. The fur of some wild animals is still coveted, sometimes pushing the market to the limit of legality – or even beyond it – harming ecological balance and biodiversity, the reason why numerous regulations and laws have been put in place. There is also imitation fur(more affordable). Certain types of cleverly designed weaves allow them to imitate the silky fur of animals. For synthetic fur, there are many variations of colour, length and distribution of hair, etc. Inverted skin relates to a sheepskin in which the wool has been preserved (as it is or sheared). These skins can generally be worked into clothing and footwear, with the wool on the inside. The outside is buffed to give it a suede appearance, sometimes it’s also given a smooth film coating to obtain a shiny leather appearance, allowing a distinction between suede sheepskin and oiled sheepskin to be made. There are different grades of sheep, Merino sheep (top of the range, silky and supple short-haired, sometimes curly), medium-fine, the Tuscany (long hair, which may be sheared), Shirling, etc. The manufacture of leather and the associated processes of conversion make it possible to recycle powder or small leather offcuts, which can be reused. Compacted together, they constitute a less costly, ‘reconstituted’ leather initially used in hidden sections of footwear, for example, but which can also be found in countless stationery and leather goods items. Synthetic leather, refers to materials made of bonded (non-woven) fabrics or fibre textiles, polyamide, for example, soaked or coated in resin (polyurethane or PVC, for example). The famous Skaï® trademark is an example of an imitation that is able to imitate leather once it has been worked. You can also find lots of leath­er imitations made of PVC, simple films calendared with a ‘leather’ pattern. Real leather, however, can also trick us into believing this. For example you can imitate crocodile or snake with cow hide. Although only a specialist would be able to notice a difference, the price of an item can be a give-way, a real crocodile bag will cost approximately 20 times more than a bag made of imitation crocodile leather The variety of chemicals used in leather processing does raise some environmental concerns. How to man­ age solid tanning waste (offcuts of leather, leather powder, etc.), the use of large quantities of water, how to treat chemical waste. More and more attention is

37

being turned towards these questions and the leather industry has already significantly reduced its environmental impact.

PROCESSING LEATHER

On the subject of fur, French researchers of the INRA (Institute Nationale de la Recherche Agronomique or National Institute for Agricultural Research), have perfected a new breed of rabbit. This so-called Orylag® is opening up a new, more acceptable and ethical path for the future, one that offers a high-quality fur (unbelievably soft, dense and bright).

Leather can be cut, sewn, glued and shaped in three dimensions (bicycle saddles, shoes). The stitching and tailoring techniques, amongst others, have reach­ed new peaks of sophistication which some large brands of leather goods have made their brand name from. It is shoes that currently constitute the main outlet for leather (at least 50%), followed by clothing (25%). Furniture also has a significant presence (15%) and the remaining leather is transformed into other leather goods and consumer products.

LEATHER AND INNOVATION Despite being relatively unaffected in terms of innovation, the leather sector is not lacking in activity. The environmental issue remains one of the big axes of improvement for this industry, which, amongst other things, has been able to reduce its consumption of water and chemical products over the past few years and develop more natural tanning solutions. There is future promise of machine washable leather, swimming trunks and space suits made of leather. Treatments, that are increasingly high-performance, allow leather to benefit from improved physico-chemical properties. For example, we see the arrival of leathers able ‘to absorb’ heat to ensure that drivers of convertible cars always enjoy car seats of an acceptable temperature. Other developments are leather and liquid ceramic combinations for a whole range of surface coatings; as well as novelties: perfumed, fluorescent, stretch leather, etc. There is absolutely no doubt that this ancient material will continue to surprise us. Tanneries also produce leather with exotic twists such as fish skin (which ironically are not always washable), cows’ intestine and stomach (small but with surprising textured effects) or frog’s skin. In the current context of sustainable development, there is much talk about vegetable leather. This expression describes both leathers that have been work­ed with vegetable tannins and a composite material man­ufactured in the Amazon from 100% cotton fabrics impreg­nated with natural latex (rubber tree), smoked and vulcanised in small furnaces, to create an appear­ance close to that of leather.

38

List of materials examined in part 02: Full grain leather

p.159 /

Nubuck – buckskin – suede p.198 / Sharkskin or shagreen p.231. List of processes examined in part 03: Assembly p.272 / Bonding

p.278

/ Calendering

Finishes ing

p.288

p.324

/ Folding

/ Stamping

p.302 p.264

p.290.

/ Cutting

p.260

/ Machining

/ Digital processes p.316 / p.268

/ Printing

p.320

/ Sew-

Metal THE IRON FIST OF MODERNITY? Of the hundred-odd atoms that we have at our disposal on earth, the majority, approximately 75, are metals. Presenting itself to man, iron erupted from the sky in the form of the meteorite. Which is where the word ‘siderite’ comes from, meaning ‘meteoritic iron’ closely linked to the French term ‘sidérurgie’ meaning ‘iron and steel metallurgy’, which has connotations of watching the substance arriving from sidereal space. Before undergoing enormous transformations, iron contributed to promoting the myth of this fascinating material, alien to man by nature, hard, cold, resistant. To master metal has always been the holy grail to allow societies to assert themselves in taking up arms, minting coins or self-defence. Resisting, was the vital, if not virile condition for subsistence in a Darwinian universe of survival of the fittest. Metals, as a result, have made their mark on history – the bronze age and iron age bear witness to this as well as, of course, the industrial revolution – the crowning moment of the metal industry, with the appearance of steel. A material which above all makes it possible to concentrate tremendous forces and constraints on tiny surface areas, something that had hitherto been virtually impossible. Steel represents the mechanical and is the material of precision. As the medium of electricity and magnetism, it is also the precursor to the arrival of the electric motor. Foreshadowing the modern world, it proves to be the ideal material for the systematic compartmentalisation of work and the organised assembly lines of mass production. Not a simple material but undisputedly a historical and social phenomenon. Steel also serves to fashion other materials. Both the object and the tool, which manufactures this object, it is recyclable. Resmelted, it is endlessly reincarnated. The stuff of dreams, on the verge of the twentieth century, metal was the ultimate material. Nevertheless, however high-performance it may be, this colossus still has its faults, as even though metal is strong, it is heavy; even if it shines like a mirror, it will never be transparent. Even if it is ‘plastic’, the quantities of energy required to transform it are considerable. These many weaknesses that in a world in which energy is in short supply have reduced metal to the status of just another material amongst many others. The metal empire has been dented on all fronts: by plastic materials in smallscale domestic objects (household electrical, packaging, food), by concrete, in construction, which offers compressive strength properties similar to if not greater than metal. In the field of high-temperature and high-resistance materials it is surpassed by technical ceramics. In order to continue to compete, the transformation of metal has left behind the empirical and turned to scientific innovation. Lightweight aluminiums have been perfected by chemists, new areas are developing: super-alloys, metals capable of high-speed deformation, metal foams, shape memory alloys, amorphous metals and superconductors…

41

METALLURGY Metals do not exist in nature as we are familiar with them in day to day life. Only some, such as copper, gold, platinum or the meteoritic rocks containing iron and nickel, are naturally available, which are referred to as being metals in their native state. It is in this form that man started to work them. Metals usually present themselves as oxides, in the form of ores and certain transformation processes are required (to reduce oxidation, amongst other things) in order to render them into a more familiar form. When they are associated with other elements such as oxygen, for instance, the metal atoms lose one or sev­ eral electrons: this is oxidation. Reduction (or deoxidation), makes it possible to regain the lost electrons thereby reclaiming the original metal atoms. Metallurgy is the term covering all of the stages of the transformation of ore into metal up to the point of manufacturing semi-finished products. The secret of reducing oxidation consists of adding a chemical element (often carbon) to the ore, at high temperature. It is in this way that hematite (iron ore) is combined with carbon in blast furnaces to produce cast iron then steel. This is also how rutile will produce titanium or how bauxite, more complex to work, nowadays ‘transformed’ electrolytically, will produce aluminium.

THE STRUCTURE OF METAL

 1

 2

Ions are atoms, which have lost or acquired one or several electrons. The structure of a metal is characterised by metallic bonds, which support the coherence of its atoms. The atoms actually share one or several electrons which constitute a combination of positive ions surrounded by a cloud of free electrons. The electrostatic bonds, which operate within the material are strong, the ionic packing is well-ordered, regular and periodic: referred to as a crystal lattice. Different models of crystal lattice can be listed, each one with a different ‘geomet­ric structure’. On a higher level, of the magnitude of the micron or millimetre, each well-ordered lattice of ions can be represented by a ‘grain’. Metal therefore acts as a granular structure, an aggregate of crystallites with varying degrees of orientation. The properties of metals are first of all determined by the constitution of the crystalline lattices of ions and then by the configuration of these lattices in relation to one another, for example, the distribution of the grains, the grain boundaries, dislocations, impurities, the intro-

42

duction of other materials, etc. A crystal always contains faults, whether they are accidental or deliberate and para­doxically, it is these faults, which determine the significant properties of the metals. It is in this way that metallurgists ply their trade and are able to propose materials with varying mechanical properties subtly perfected.

PROPERTIES OF METALS The important properties of metals depend on their specific molecular structure. This will determine how they are processed and their ability to meet the ments of specifications for components, obrequire­ jects or metal structures. Metallic glint One of the important characteristics of metals lies in their metallic glint. These materials, once polished, can reflect light to such an extent as to render a perfect image, like mirrors (with tin, silver or aluminium depos­ited on a plastic or glass substrate). Metals are also responsible for achieving tinted and reflective effects which can be found, for instance, in paints or other mat­erials. A ‘metallised’ plastic component, for example, either contains metal as a solid mass or a metallic deposit on its surface. Hardness This is a component’s resistance to penetration and abrasion of its surface. Hardness is, when you think about it, a completely relative notion. However, metals are amongst the hardest of materials. In fact, they often constitute the material of which tools are made. Attain­ing ‘harder than hard’ is one of the great imperatives of today in terms of research and development. Resilience This is impact resistance, the capacity to absorb a mechanical energy in a small amount of time, at a given temperature. A material with weak resilience is said to be brittle. In the case of steels, for example, the colder the material is, the more brittle it is and the more you increase its temperature, the more the material will be able to be processed. Elasticity This is its ability to return to its original shape after being stressed. Steel and metal alloys can generally be considered as being perfectly elastic up to a certain point, referred to as their ‘elastic limit’. A prime example of elasticity is its use in springs.

 1

EXAMPLES OF CRYSTAL LATTICES

 2

1 2

grain interfaces

3

CRYSTAL STRUCTURE OF A METAL 1 ordered ion lattice 2 grain or crystallite 3 grain clusters

43

Plasticity / Ductility Once a metal has reached its elasticity limits, plasticity occurs. Plasticity will be its ability to be subjected to a permanent and irreversible deformation without break­ ing. This quality is compatible with cold methods of processing the material, such as bending or shaping. Ductility, the ability to stretch without breaking, is the challenge of the material’s plasticity. Gold is the most ductile metal: 1 g of gold can be stretched into a 2.4km thread without snapping. Magnetism Metals are materials with the specific ability to develop magnetic phenomena. Historically, magnetite, found in some ferrous deposits, is the component material of magnets. However, some metals are also magnetic or easily magnetisable, such as iron, as well as steel, nickel or cobalt. Once intro­ duced into a magnetic field, they can become perma­­­­ nent or temporary magnets, or even electromagnets. The magnetic properties of metals also make it possible for us to identify them. Aluminium and some stainless steels do not react to the power of a magnet. These are referred to as being non-magnetic. Isotropy Metals are commonly considered to be isotropic materials, that is they display the same behaviour in all three directions in space. However, their crystalline structure and the method of production of metal semi-finished products (rolling, drawing or extrusion…), induces some orientation within the material, revealing some anisotropic characteristics. It is often overlooked but is no less real. Conduction of electricity Metals are generally good conductors of electricity, particularly silver, copper, aluminium and gold. This property is explained by the type of metal bonds, which allow the circulation of free electrons within the crystal lattice. These conduct electricity through the material. Conduction of heat and expansion For similar reasons, metals are generally good conductors of heat. When you increase the temperature of a metal, it expands. This expansion is generally reversible. A 1m long steel bar will stretch by 1.2 mm between 0°C and 100°C. This is therefore a very important characteristic to take into account in the design of metal components, particularly for moulding or welding, where expansion and contraction can cause deformations or even cracks.

44

ALLOYS Metals are rarely used in their pure form. By combining a metal with one or several other (metal or non-metal) elements, you considerably enhance the properties of the new material obtained: the alloy. It is the famous ‘magic formula of: 1+1=3’. The principal component of the alloy is the base metal, the added elements, alloy elements, play a part even in small quantities. Alloys come in a variety of ‘grades’, that are constantly being enhanced. Historically, one of the first alloys that man worked was bronze (copper and tin). Iron and carbon alloys provide the famous cast iron and steels. Steels, in turn, can be alloyed with a number of additional components, which make it possible to subtly vary their properties. For example, the much celebrated stainless steels consist firstly of iron and carbon alloy to which chromium is added and then, according to requirement, nickel, molybdenum, vanadium, etc. Stainless steels are characterised by their corrosion-resistance. Aluminium can be combined with zinc to form zamac (die-casting zinc alloy), for instance, or even with copper, magnesium, or manganese. Alloyed with zinc, copper forms brass but it can also be combined with nickel or aluminium, for example, which is referred to as copper-nickel or copper-alumin­ ium alloys.

IRON AND STEEL METALLURGY Iron and steel metallurgy relates to the metallurgy of iron-based alloys, cast irons and steels, in particular. Two development processes currently co-exist: • The ‘cast iron’ method: Cast iron is produced as a result of adding carbon to iron ore, provided by coke (coal) in blast furnaces. Once liquid, cast iron is transferred into an oxygen converter to lower its carbon content and becomes steel. At this stage, it is referred to as ‘wild’ steel. As a result cast irons have a carbon content of between 2 and 6% whereas steels do not exceed 2%. • The ‘scrap metal’ method: Steels are produced as a result of recycling and recasting recycled components. Wild steel is obtained as a result of putting this scrap metal into an electric furnace. This method of recycling is far from being negligible in terms of production. Along with glass, it is in fact one of the first methods to have been implemented for the industrial recycling of materials. The two methods are combined to refine wild steel and to formulate different grades of alloy according to the final requirements. Then comes hot or cold rolling,

 3

 3

1

2

3

4

cast iron

O2

5

6

7

steel

8

9

10

11

12

MAIN OPERATIONS IN the PRODUCTION OF CAST IRON AND STEEL 1 ore 2 coke 3 blast furnace 4 ferrous scrap 5 oxygen converter 6 electric furnace 7 secondary furnace 8 slab or bloom 9 billet 10 rolling mill 11 iron and steel flat products 12 iron and steel long products

45

 5

where the material is progressively crushed. This is the final stage before finally obtaining long iron and steel products such as coils of sheet metal, sheets, beams or steel wire.

TREATMENTS The mechanical properties of metals can be modified by heat treatments, once the components have been made. The structure of the material can then be mod­ ified. There are three major types of treatment: • Annealing: The metal component is heated (between 500°C and 850°C), maintained at this temperature and then slowly cooled. In this way the internal tensions of the metal are released, making the material more malleable. An equilibrium structure is regained. • Quench hardening: In the same way, the component is heated (> 800°C for steels, for example), maintained at this temperature then cooled abruptly (in water, oil, air or gases). Two types of hardening are possible: solid or superficial. The metal then becomes very hard but brittle. • Tempering: Once hardening has been completed, the component is reheated, amongst other things, to minimise the embrittling effect of the quench hardening.  4

It is also possible to undertake strain hardening. This alters the state of the metal in order to make it harder by plastically deforming it cold. Paradoxically, the term also actually refers to a strain fault, which will occur by dint of making demands on the material until a strength quality is attained, specifically, by subjecting the material to this strain beforehand.

CORROSION All metals are subject to corrosion, to varying degrees, more or less visible and depending on the climatic conditions to which they are exposed (degree of moisture, temperature, etc.). It is an irreversible degenerative reaction associated with contact with oxygen, that is commonly referred to as rust. Metal is in fact simply returning to its natural oxide state. The most vulnerable metals are cast iron and steel; copper, brass and bronze are quite resistant to corrosion; aluminium and zinc are very tolerant and silver, chromium, titanium and gold are exceptionally resis­ tant to it. To be protected from corrosion, steel is combined with chromium, for example, to produce a stainless steel. It can also be coated with other metals such as zinc

46

by electro-zincing or galvanisation, such as chromium for chromium plating. It can even be painted, enam­ elled or varnished thereby slowing down the rusting process. In turn, aluminium can be anodised. Its surface is chem­ ically treated by electrolysis and is then treated with a layer of protective aluminium oxides, anodisation, which can produce tinted effects. Some metals create what is referred to as a passivation layer, a type of self-protection, in the form of a superficial corroded layer which, paradoxically, protects the core material. In some cases in which different metals co-exist, types of corrosion can also be witnessed created by a ‘galvanic effect,’ which takes hold between the two. The roles of anode and cathode are spread out and some electrons migrate from one metal to another, embrittling one of the two. Combining different metals with one another thus requires special attention at the design stage. This phenomenon is consciously used specifically to preserve some components. A metal is introduced (often zinc or magnesium), which will act as a sacrificial anode and will corrode in place of the protected component. Steel ships are protected in this way, by pieces of zinc ‘patched’ over the hull. Similarly, galvanisation (zinc treatment) to steel also helps to protect it.

Metal and innovation The largest areas of innovation in metallurgy focus on enhancing what are already very high-performance materials. These innovations, not necessarily spectacular, nonetheless represent important breakthroughs. Mak­ing it possible to face the crucial technical problems in developing, for example, methods of producing heat energy at high temperatures, transporting these energies and the safety of these installations, as well as applications in the automotive or construction sector. Of course, increasingly fine control over nanotechnologies will further enhance advances made in metallurgy. The properties of so-called ultra-high-temperature metals (nickel-based super alloys, for example) or ultra-low-temperature metals (aluminium- and titaniumbased alloys, for example) will make the necessary advances. Which could limit the risks of serious accidents (industrial disasters of the type of the sinking of Erika) or otherwise increase the safety of the manufacturing of nuclear power reactor tanks. In the design of road vehicles, the appearance of met­als capable of very high-speed deformation, able to absorb the energy from front impacts at speeds great­er than

 4

1

2

3

MODIFICATION OF STRUCTURE OF ROLLED METAL

ALLOYS

Density (kg/m3)

COMMONLY ALLOYED METALS

Melting point

PRECIOUS METALS

Symbols

BASE METALS

Metals

1 metal grain 2 strain hardening 3 re-crystallised crushed grains

Aluminium

Al

660°C

2700

Copper

Cu

1090°C

8920

Tin

Sn

232°C

7310

Iron

Fe

1535°C

7860

Mercury

Hg

–39°C

13600

Lead

Pb

327°C

11300

Titanium

Ti

1660°C

4500

Zinc

Zn

420°C

7140

Silver

Ag

960°C

10500

Gold

Au

1063°C

19300

Platinum

Pt

1764°C

21400

Chromium

Cr

1857°C

7140

Cobalt

Co

1490°C

8900

Magnesium

Mg

650°C

1750

Molybdenum

Mo

2625°C

10200

Nickel

Ni

1452°C

8900

Vanadium

V

1890°C

6100

Antimony

Sb

630°C

6697

Bronze

Cu + Sn

~900°C

8400 - 9200

Brass

Cu + Zn

~940°C

7300 - 8400

Zamak

Zn + Al

~400°C

6600 - 6700

Cast iron

Fe + C

~1100 - 1300°C

~7800

Steel

Fe + C

~1500°C

7800 - 9000

MELTING POINT AND DENSITY OF THE PRINCIPAL METALS AND METAL ALLOYS

47

1

2

4

6

3

5

7

STEEL PROFILE PRODUCTS 1 IPE beam 2 / 3 INP beam 4 / 5 HE beam 6 / 7 equal-flange T profile, unequal-flange T profile

48

 5

1

2

3

4

6

7

8

9

10

11

5

STEEL PROFILE PRODUCTS 1 UNP profile 2 UPE profile 3 angle steel (unequal angle) 4 angle steel (equal angle) 5 round 6 square 7 hexagonal 8 flat 9 welded tube 10 seamless tube 11 square or rectangular section tube

49

60 km / h is promising. These metals can be affected by positive changes of phase and structure locally during a crash. The development of metal foams (aluminium, amongst others) also holds significant advantages. Foams actually have impact damping properties and embody a weight advantage in relation to solid structures. Please note: a highly prospective field of development includes superconductors, which are materials that experience a rapid decrease in their electrical resistance at very low temperatures (4.23 K or -268,77°C for mercury; 1.19 K or -271,81°C for aluminium). The preparation of alloys of this type now makes it possible to do away with absolute zero temperature and makes cooling with liquid helium or, even more simply, with liquid nitrogen possible. What still appears to be but a scientific pipe-dream – although it does not appear to be impossible – would be to manufacture ambienttemperature superconductors, allowing electrical current to flow without any (or very weak) losses. Interest and requirements associated with the development of these materials in relation to the transportation of energy is being measured. In the field of electronics, there are plans to use these superconductors to replace silicon-based electronics, where the limits of performance are now within sight. In the even more floundering field of magnetic levitation, designs for floating trains are at the prototype stage.

mak­es it possible to design more light-weight structures. A weight advantage, which might prove to be a real environmental benefit (less material but higherperformance, less transportation, etc.) There is also a tendency towards ready-to-use, semifinished products (in order to compete with other materials). Corrosion resistance (for architecture or automotive applications) remains one of the biggest areas of research as well as sound insulation (sound-insulated composite steel-polymer sheets).

The metal shape memory alloys (shape memory polymers are also available) continue to constitute some astounding materials. Their ability to ‘remember’ one or two shapes that they can constantly return to within certain predetermined temperature ranges, whatever deformations that they may have suffered, has long been the reserve of military applications. Today these are surfacing in mechanical and medical applications (small spirals, which are deployed in an artery called stents) or even textiles (clothes, which return to their shape without ironing, for example). These alloys are extremely reliable compared with conventional mechan­ics. As we have seen, metals have a crystalline structure. However, metals with an amorphous structure have recently become available. These types of ‘metallic glass’ represent a real revolution. Their structure provides greater elasticity, better response to moulding, high levels of strength and hardness and corrosionresistance. These special alloys have even surpassed titanium.

List of materials examined in part 02: Alucobond® minium (Al) (Cu)

p.143

(Pb)

p.178

50

/ Brass

/ Foams

p.158

p.129

/ Gold (Au)

/ Liquidmetal®

tic materials

p.189

/ Bronze

p.186

p.130

p.168

/ Cast Iron

/ Honeycombs

/ Magnesium (Mg)

/ Shape Memory Alloys

p.230

p.121

p.134

p.170

p.188

/ Alu-

/ Copper / Lead

/ Magne-

/ Silver (Ag)

p.235

/

Stainless steel p.238 / Steels p.239 / Tin (Sn) p.241 / Titanium (Ti) p.242 / Zamak Alloys p.252 / Zinc (Zn) p.253. List of processes examined in part 03: Assembly ding

In the field of construction, head to head with concrete, high-yield-point steel (HYP) gives birth to a range of stronger steel products. Amongst other things, this

p.122

p.278

/ Calendering

p.302

/ Cast moulding

Digital processes

p.316

p.264 /

/ Founding

p.304 /

Forging

p.294

/ Extrusion p.292

p.308

p.298

/ Finishes

/ Heat sealing

p.272

/ Bon-

/ Cutting p.324 p.284

p.260 /

/ Folding / Injection

Machining p.268 / Printing p.320 / Sintering p.296 / Stamping p.290.

Glass, cera­­m­­ics GLASS, THE transparent mystery If the purpose of a material is to b­e seen in order to assert its existence, glass is a paradoxal material, it stands out by going unseen. Dissolving into light and yet still existing, painters such as Magritte have been stumped by the question of how to portray it, opting in the end to show only the frame which contains it. As the only transparent and solid body available for use for a long time, the fascination with glas­­s has spanned centuries. Its mystique drawn from the improbable internal arrangement of silica, in a vitreous state. Glass was long considered as a precious commodity. Its history has been one of a race for purity; for absolute transparency. Glass lets us see, gives us the constant promise of the other side, as it did for Alice as she passed through Lewis Carol’s forbidden looking-glass. A shop window works in exactly the same way; offering us the provocative illusion of stealing for one’s own the objects on display, without ever touching them. Just as desire itself is born, so glass comes into its own. An enchant­ ing material, glass creates attraction and repulsion alike; being both incredibly hard and yet fragile at the same time, its potential destruction always hanging over it, stunning, dangerous and irreversible. Glass has always held a symbolic and sometimes technical, place in the practice of architecture. From stained-glass windows to entire glass-houses, architects have used this material to express the most subtle of abstractions and metaphors. An expression of architectural modernity, glass plays a fundamental role in drawing the line between public and private spaces. Nowadays it has become the number-one instrument in dramatising subtle changes in décor conceived by architects. At the beginning of the 20th century, industrialised mass production, in addition to the emergence of polymers as a worrying rival, meant a deglamourising and popularising of transparency in all sectors where glass had previously reigned: household wares, packaging, architecture. Glass is now rebuild­ing itself around new values. It has become a mediator, a vector for information. Far from being endangered, glass production continues to progress thanks to the addition of new properties: optical, mechanical, electrical and thermal. It even learns from its worst enemies, the polymers, in order to produce laminated glass – a true revolution in terms of protection and security. Glass is also refining its very composition and can now be processed en masse, tempered, coloured, made into a conductor and technology is in the process of making glass which can transmit or reflect variably, at the flick of a switch. Fibre optics – so far removed from simple, flat window glass – have already allowed glass to enter the world of textiles and electronics and thus foresee a future in all dimensions of space. Undoubt­ edly glass must be placed amongst the ranks of the ‘intelligent materials’. The extraordinary mastery of glassmaking techniques gives us the freedom to play with glass like a huge sieve; filtering duties, sensations and emotions, which could mean that Alice’s Adventures might truly become our own.

53

MINERAL MATERIALS AND THE ART OF FIRE Grouping glass and ceramics together in this chapter is no matter of convenience or coincidence; these two mediums are very closely related thanks to their con­ stituents (minerals), the similarity of their production methods (heating) and by the specific qualities which characterise them: Glasses and ceramics are made from mineral material (silica sand for glass and clay for ceramics) and must be subjected to a relatively long heating process to become usable. The rise in temperature makes them undergo an irreversible physical and chemical transformation. Legend has it that glass was discovered by accident more than 6,000 years ago by Phoenician merchants. The merchants had made a large fire on the beach and were intrigued by the block of hard, dense, vitreous material they discovered the next day amongst the cooled ashes of the fire. It seems more likely, however, that the discovery of glass was part and parcel of the first ceramic and pottery kilns, as it is very difficult to fire earths at very high temperatures without a bit of sand turning into glass. The first rudimentary glass might well be contemporary with the first functioning kilns (around 5,000 BC), glass then being closely linked to ceramic production from that point onward via decorative and protective glazing. Glass and ceramics are very hard materials which resist high temperatures and are generally good electrical and thermal insulators. They have very low elasticity and break easily without being subject to a plastic deformation phase. However, there is one fundamental difference distinguishing the two materials. As temperature rises, silica goes into a liquid phase, whereas clays solidify without a liquid phase. This simple detail completely changes the finished product. Liquefaction of silica gives it its principal distinguishing feature: an irregular atomic structure which gives transparency to the solid obtained (glass).

GLASS The invisibility of glass is almost supernatural. Before the advent of plastic materials, only air, open space and possibly water knew the enigma of transparency. Glass, by this optical peculiarity, is therefore one of those rare materials which manages to trick nature (flies and birds alike are fooled by transparent window panes). This ideal of invisibility has fascinated for millennia and has also been a recurring source of

54

inspiration – from the myths and legends of Ancient Greece to H.G. Wells’ The Invisible Man. Glass is an amorphous solid obtained by the cooling of a molten liquid: • When a solid is heated; it starts to liquefy at a defined and fixed melting point. Conversely, if we decrease the temperature, the liquid will become solid once again at the same temperature (melting point). If the material concerned can be cooled to below its melting point whilst retaining to some extent its liquid state, this is called supercooling. In the case of glass, we see that liq­uid silica can be cooled to below its melting point with an increase in viscosity, whilst still remaining liquid. • In most materials and indeed throughout most of the solid state, atoms are organised according to a very precise arrangement (in crystalline or semi-crystalline structure, for example). This arrangement stabilises and compresses the material. In the case of molten glass, the liquid sets gradually whilst still keeping its irregular atomic structure (vitreous state). The material is therefore said to be non-crystalline, or amorphous. A vitreous state is an ‘intermediary’ state, which is just as distinct as the other ‘liquid, solid and gaseous’ states. Glass is essentially made of silica (sand), soda and lime, but vitreous materials based on other constituents can be made. Nowadays, there are what are known as metallic glasses, in other words metals which, in a solid state, have an irregular atomic structure (see Liquid Metal® p.186). More mundanely, caramel is nothing more than vitrified sucrose, or fixed liquid sugar! Glass is the paradoxical material par excellence. It is a solid with the structure of a liquid, a brittle and rig­ id material at ambient temperature and yet extremely plastic when heated. It just loves to baffle us. Glass – amorphous – can be made from quartz, for example, which in itself has an obvious crystalline structure!

COMPOSITION OF GLASS There is huge variety in the characteristics of glass available, according to the composition and ratio of ingredients which are designed to fit the desired properties and usage. Unlike the strict and rigid framework governing crystals, the irregular atomic structure of glass gives scope for the integration of foreign elements. However, certain constituents are always necessary: • Glass Former: Essential base constituent; generally silica, as sand. • Flux: Soda, sodium or more often, alkaline oxides. These lower the melting point. Pure silica melts at

around 1,800°C. By mixing it with oxides, melting can occur from 1,400°C. • Stabiliser: Adding lime makes the glass more stable and inert and, more notably, makes it insoluble in water. • Additives: Along with the basic silica, sodium, calcium mixture (the batch), an extensive list of additives may be used to improve the optical qualities (refractive index, optical transmission, colour) or the physical qualities (malleability, thermal stability). First and foremost amongst the palette of glass compositions are three main examples: • Crystal: Adding lead in large proportions changes a number of the characteristics of glass. The presence of this heavy metal lowers the working temperature, lengthens the cooling time and increases hardness after cooling. It aids cold cutting and polishing and above all, improves the sparkle of the glass by increasing its refractive index. This discovery won the Venetian glassmakers their fortunes, followed by their English, French and Bohemian counterparts. It should be noted that the word ‘crystal’ is a misnomer since the material is still amorphous and not crystal according to the laws of physics! By upping the percentage of lead in the glass (to great­er than 50%), we get paste, also known as strass (after an 18th century jeweller from Strasbourg), which has a very high refractive index and is used in the man­ ufacture of costume jewellery. (See Crystal p.145) • Borosilicate glass (Pyrex®): Adding boric oxide greatly lowers the expansion coefficient, leaving the glass much less susceptible to thermal shock. Pyrex® is therefore a glass which can withstand large differ­ ences in temperature within very short periods of time. It does not deform at high temperatures. It is used for ovenproof kitchenware, laboratory and industrial equip­ ment and the construction of reflecting telescopes and bendable tubes for neon signs. (see Glass, borosilcate p.156). • Vitro-ceramic: Glass which has been ‘devitrified’, or rather, crystallised, by the addition of oxides which aid crystallisation and by precise control of the solidification temperature levels. Vitro-ceramic has dimension­ al stability, exceptional thermal resistance and much great­ er mechanical performance (resistance and strength) than normal glass. Vitro-ceramics, naturally, have to sacrifice their transparency and are generally translucent or opaque. (See Glass, vitro-ceramic p.167).

Transparency The lack of light diffraction over this solid makes it more or less completely transparent, depending on its composition, purity and the care given to its man­ ufacture. However, glass is not transparent under the entire spectrum of light. Under ultraviolet and infrared lights, a large amount of absorption occurs; glass will there­ fore appear opaque. This phenomenon explains why we are partially protected from UV rays behind a window. It also explains how a greenhouse works; the infrared radiation being trapped by the glass roof. In the visible part of the light spectrum, glass is transparent. Stability Glass is isotropic, in other words, its properties are independent of directions of space. It is therefore a directionless medium. In the commonest temperature range of use, glass has very good stability, varying only slightly with temperature change. Instability Paradoxically, despite the appearance of durability which glass exudes for us humans, it is in fact a fundamentally instable material. On the one hand, it slowly but surely crystallises, gradually becoming opaque and powdery and on the other hand, it still remains fluid and so continues to flow and sag. Insulation Thermal inertia and thermal expansion make glass a good thermal insulator. It is also an electrical insulator at low temperatures, but becomes a conductor when sufficiently heated. Glass also acts as a good dielectric and resists strong electrical fields well. Inertia Glass is a ‘closed’ material, it is relatively inert chemically speaking and resists most acids and bases. It is not susceptible to UV radiation, oxidation or atmospheric erosion. Density The density of glass is in the region if 2.5, which is roughly the same as that of classic concrete. To put it another way, a 1 mm thick sheet of flat glass has a mass of 2.5 kg per m2. If it contains a lot of lead, this density can be six or above.

PROPERTIES OF GLASS As we have seen, glass has an irregular atomic structure. It is precisely this amorphous state which gives this material its main paradoxical properties.

Duality This infinitely viscous liquid is hard and brittle at ambient temperature, but we can alter its viscosity by heating it, when it can become malleable and plastic.

55

Recyclability Glass is, without doubt, one of the first materials to have undergone recycling, either via direct reuse (the qualities of inertia and durability of glass make it highly reusable, requiring no more than a good clean) or following full recycling, including sorting and grinding, to be reintroduced into the manufacture process as some kind of cullet. While certain technical glasses raise a number of recycling issues, everyday glass can be indefinitely recycled without detriment to its quality.

GLASS TREATMENTS Annealing After shaping at very high temperatures, a piece of glasswork (whether drawn, cast, pressed, blown or from float production, etc.), will be subject to very large tensions caused by the differences in temperature gradient. If nothing is done to rebalance the material, these internal tensions can literally explode the piece. The aim of an annealing treatment is therefore to bring the strain down to an acceptable level, by reheating the glass and then to lower it to an ambient temperature by means of slow, controlled and consistent cooling. This process allows for normal cutting of glass. Thermal tempering This treatment simply plays on the internal tensions of glass, but in a controlled way. The procedure consists of heating the object in question to its softening (annealing) point and then rapidly cooling the external surface with forced draughts of air (in a matter of seconds the glass goes from 600°C to 300°C). This temperature difference between surface and inner portion creates a state of permanent stress in the glass, compressing the surface. The glass now resists compression to a much greater extent than expansion. This tempering process gives the glass increased mechanical properties. Glass must be cut to size before the heat tough­ening process. When hit by a concen­ trated impact, the glass breaks into lots of smaller, safer fragments. Chemical tempering Chemical tempering also involves creating tensions, by modifying the chemical composition of the glass object’s surface. The piece is submerged in a solution of molten salts and the whole lot is heated to 400°C, chemical exchanges then occur which compress the outer surfaces. Compared to thermal tempering, this technique has the added advantages of being viable for very small or complicated pieces and imparting mechanical properties which are up to five times great­er.

56

GLASS MANUFACTURE Delivered in the form of certain rocks (obsidian and tektite), glass exists naturally, without human intervention. Lightning can also ‘produce’ glass when it strikes on sand and heats it up very fast (fulgurites, or petrified lightning). The world’s primary producer of glass is not man, but small unicellular algae (diatom) found at the bottom of the sea! This rudimentary plant can make itself complex glass shells thanks to a chemical process which remains little understood. It synthesises glass from the silicates present in the water (a method which does not involve melting, known as sol-gel). A constituent of plankton, the mass of glass produced this way is so large that it far outstrips human production. The manufacture and working of glass has undergone numerous evolutions in its history. It started with crude casting and moulding of impure vitreous matter to obtain small or chunky objects (beads, balls and glazes) to the magnificent glasswork of Murano, Bohemia and Baccarat, which called upon alchemical science and unpar­ alleled knowledge. One of the greatest (r)evolutions of this material took place in the middle of the 20th century, when English company Pilkington put the finishing touch­es to a production method which was to give us float glass. This production method for flat glass fin­ ally allowed large-scale industrialisation, making 1kg of glass cheaper than 1kg of potatoes! Today, most flat glass is manufactured using the float method. The main techniques employed for other glasses being blow moulding for hollow pieces, or extrusion for glass fibres and wools. Traditional and semi-industrialised glass production still survives for blown and drawn glass, most notably for glass blown on a rod, sand moulding, fusing (small fragments of glass melted and assembled), glass mosaic and enamel work. Drawn glass The principle of drawn glass was perfected at the beginning of the 20th century and was the first industrial production method of flat glass. The sheet of glass is repeatedly stretched out vertically having been passed through the slot of a heat-proof piece of equipment known as a ‘debiteuse’ or ‘debi’ for short (a ceramic die), submerged in a bath of molten glass. Float glass The ‘float’ procedure, perfected by Alastair Pilkington in 1952, uses a mixture of primary materials, continuously loaded into the melting furnace. Upon exiting the furnace (at approximately 1,000°C), the liquid glass forms a ribbon, floating on the surface of a reservoir of molten tin. The surface of the tin is extremely smooth, giving

 2

 1

 1

2

1550°C

3

1

4

5

6

PRODUCTION OF FLAT GLASS: FLOAT-GLASS PROCESS 1 oven 2 molten glass 3 bath of molten tin 4 float 5 annealing lehr 6 cutting

 2 technical glass (2%) (insulators, optics, laboratories, etc.)

glass containers (78%), (bottles, flasks, jars, etc.)

4

1

3

glass fibre (4%) (insulation, textiles)

flat glass (16%) (windows, mirrors, etc.)

GLASS APPLICATIONS

2

1

DIAGRAM SHOWING PRINCIPLE OF GLASS DRAWING 1 bath of molten glass 2 debiteuse 3 solidified glass 4 drawbar

57

the glass a perfectly flat surface. The natural thickness of this glass ribbon is 6mm, but larger or smaller thick­ nesses are easily obtained by speeding up or slowing down the spread of the molten liquid. The ribbon of glass is then slowly cooled until completely hard, cut into 6,000 x 3,210-mm panels and conditioned. This technique, so conceptually simple and yet so difficult to perfect on a practical level, offers a vast array of advantages over previous technologies: • Production is continuous, giving large sizes and mass production. • Resulting glass is totally flat, with smooth, shiny surfaces and no polishing is required. • Regular thicknesses are obtained, giving a totally standardised product. • Imperfections such as bubbles, striations, chord and lines do not occur. The glass is perfectly flat and transparent and void of optical defects and deformities. Since its implementation, the float process has proved so efficient that it very quickly overtook all other methods of flat glass production and introduced glass to mass consumption, big building projects and the industrial era. However, float glass is so perfect that in fact there are some situations where it cannot be used. This is particularly the case in restoration work for old buildings, where it may be detrimental to use a glass which does not have the same look and imperfections as the original windows. Similarly, the mass production inherent to the technique does not allow for non-standard products (coloured glasses, glass with special effects, varying thicknesses, opalescence or opaqueness, specific physical characteristics). There shall always be a place for semi-industrial production of flat glass, using less efficient but more flexible techniques, such as glass drawing.

Self–cleaning glass: Glass with a layer of titanium dioxide. The titanium oxide acts as a catalyst by a photo-catalytic effect. Under the effect of UV rays, this decomposes organic particles (greasy marks). • Liquid crystal glass: Laminated glass made of two sheets of glass and two insert films, in between which an LC film (holding liquid crystals) is placed. At rest, the crystals sit in irregular directions, so the glass is translucent with a frosted effect; when subjected to an electrical field, these crystals align themselves and the glass becomes transparent. •

Current research is being carried out on the thermal insulation properties of glass, which will hopefully give rise to the advent of insulating glazing even more efficient than standard, opaque partitions. Glass aerogel, about 95% air and the rest glass, has exceptional insulating properties. Holding a block of what has been nick-named ‘frozen smoke’ is said to feel no heavier than holding air! New methods of producing glass without melting (solgel) are also very promising and pave the way for effective surface treatments in very thin layers. This may provide an opportunity to make so-called hybrid glass, where the mineral enhances the organic (the latter hav­ing low heat tolerance, amongst other problems). Other research is being done into luminous and superlight glass. Last but not least, glass is also used in the treatment of radioactive and toxic waste (purification residues or household wastes containing heavy metals, for example). Waste can be contained and confined by vitrification in borosilicate glass.

GLASS AND INNOVATION The refined composition of glass, using multiple additives (laminated, coatings) is giving a wider range of qualities and functions to the glassmakers of today. Nowadays we have: • Heat and light reactive glass: Glass which chang­e s colour under the influence of temperature change or UV rays. • Electro-chromic glass: Glass which changes col­ our under the influence of an electrical field (which can be fully adjustable and controllable). • Heating glass: A new generation of glazing which is used in building and household electrical appliances, made using a conductive metallic layer (those with low-emissivity coatings obtained through pyrolysis), which generates heat.

58

List of materials examined in part 02: Aerogels tal

p.145 /

(Pyrex®)

Fibres, glass p.163 /

p.153 /

Glass, coated

Glass, 3d p.164 /

p.162 /

p.120 /

Crys-

Glass, borosilicate

Glass, security – safety

p.165 /

Glass, toughened p.166 / Glass, vitro-ceramic p.167 / Mirrors p.194. List of processes examined in part 03: Assembly p.272 / Bonding

p.278 /

Calendering

Digital processes p.264 /

Heat sealing

forming p.314.

p.302 /

p.316 / p.284 /

Cast moulding

Extrusion

p.308 /

Machining

p.268 /

p.298 /

Finishes Printing

Cutting p.324 / p.320 /

p.260 /

Folding Thermo-

glass glass dehydrated air metallic armour

double glazing

armoured glass

glass

glass

PVB

PVB

metal layer

glass laminated with PVB

glass laminated with a metal layer

glass PVB

polyurethane (plastic interleaf) polycarbonate (with anti-scratch protection) composite laminated glass

characteristic shattered fragments of toughened glass

COMPOSITE GLASSES

59

COMPOSITION OF CERAMICS Made by firing and generally from, clay, quartz (silica) and feldspar, traditional ceramics are porous materials which have vitreous (amorphous) and crystalline phases. Clay’s main constituent is kaolin, with a relatively large proportion of metallic oxides – impurities which affect the colour of the finished product. Feldspar plays the role of a fluxing material, cementing the kaolin and silica particles and reducing porosity. Feldspar also gives rise to the vitreous phases. Following the irreversible firing of traditional ceramics, the water content in the original mixture evaporates.

 3

By varying and supplementing the basic ceramic recipe, the performance levels and characteristics of the product can be controlled. Other elements involved in the composition of ceramics are: mica, talc, chamotte (ground bits of fired refractory ceramic), limestone, magnesia. So called ‘technical’ ceramics, truly booming at the moment, are synthetic materials, mostly made of oxides, carbides, nitrides, borides, sulphides, titanates, zirconia, etc., according to the desired final properties.

CHARACTERISTICS OF CERAMICS Ceramics have a structure characterised by: • Few or no free electrons: Ceramics are therefore bad conductors of electricity and heat. They are used as electrical and thermal insulators. However, some ceram­ ics are semi-conductors and others are piezoelectric. • Particularly stable and strong ionic and covalent bonds: Ceramics therefore have very high melting points. They may, for example, be used as refractory equipment in furnaces. In addition, the chemical stability of the bonds gives ceramics a certain level of resistance against environmental factors. Largely chemically inert, they do not readily degrade by corrosion or oxidation. The strong bonds also give rigidity, however, ionic crystal dislocation can occur and the covalent bonds are not very flexible. Ceramics therefore remain brittle and break with no plastic deformation, except when very near their melting point.

The word ‘pottery’ is of Latin origin (potum) and refers to the use of drinking vessels. Nowadays, the word ‘ceramic’ is used to describe everything which can be made of clay: from tiles to hand-made plates, thrown or lathed, to toilets and not forgetting spark plugs! The word ‘pottery’ refers to hand-thrown pieces, made on a potter’s wheel. Terra Cotta Terra Cotta is a permeable, unglazed ceramic. Some types of terra cotta can be used to make refractory equipment. Terra cotta is used to make tiles or bricks, for example. Earthenware Earthenware refers to red clay, with high iron content. Fired at a low temperature (less than 1,100°C), it makes up a large part of total clay used. It may also be creamy white or black. Earthenware is certainly one of the old­ est and most widely-used techniques. Earthenware pieces are porous and must be glazed. Many floor and wall tiles are earthenware. Porcelain Porcelain is a white clay fired at high temperatures (a­bove 1,250°C). If made very thin, some porcelain can be translucent. Porcelain is an impermeable cer­amic which is often used for tableware or decorative objects. Stoneware Stoneware is a grey or brown clay which, following fir­ ing, often has black or dark brown specks (which correspond to iron aggregates – pyrites – or other metals). Firing temperatures vary between 1,200°C and 1,400°C. Stoneware stays opaque and is impermeable. Stoneware is used for tiles and stoneware close to porcelain it is used for sanitary ware. Finishes (colouring) do not come out the same across the board of ceramics, due primarily to their different firing temperatures. However, it is not always easy to distinguish between these different materials.

SLIP, PASTE and POWDER CERAMIC, POTTERY, EARTHENWARE, porcelain or stoneware  Ceramic and pottery The word ‘ceramic’ is of Greek origin (keramikos) and refers to animal horn; the first material used for drinking vessels. ‘Ceramic’ was also the name of an area of Athens where the tile and brick workshops were located.

60

To make traditional ceramic pieces either slip, paste, or powder/thermoplastic composites are prepared. • Slip: Is a liquid suspension. The primary materials are first ground and then mixed to form, with the addition of water or another binder, a suspension ready to be cast or injected. The viscosity and thixotropy of the slip (variation of viscosity according to flow speed) governs the slip’s behaviour and the success rate of the above methods.

 4

 3

quartz

wall tiles

electrical porcelain

bricks

transparent porcelain

hard porcelain

soft porcelain

floor tiles

dental porcelain

FELDSPAR

kaolin

composition of different types of ceramics

 4 other

sanitary ware (vitreous)

TECHNICAL CERAMICS

tiles bricks / tiles (ceramic tiles, (earthenware) decorative ware) refractory products (earthenware)

crockery / ornamental ware (porcelain)

TRADITIONAL CERAMICS

main applications of ceramics

61

Ceramic paste: Is obtained from enriched liquid paste. The water from slip is removed by means of a filter press which produces flat firm pancakes of paste. These pancakes are then made into rolls by an extruder. The plastic paste is thus ‘conditioned’ and worked once more by extrusion (to make hollow bricks for example), by pressing (tiles and crockery) or by jiggering and jolleying (classic potter’s techniques which use a rotating mould and a shaped tool to give the contours of flat and hollow pieces respectively). • Powder: Powder of a pre-fired ceramic is mixed with a thermoplastic. The whole lot is injected into a mould and then fired once to eliminate the thermoplastic bind­ er and a second time to insure grain cohesion within the ceramic. This is known as ceramic sintering. This procedure is relatively recent but full of potential; many ceramic techniques already make use of sintering.

•

FIRING OF CERAMICS Once cast, injected, pressed, extruded or thrown etc., the pieces are then dried – in the open air or inside – then fired. This firing takes place in one or more stages. In the case of earthenware, for example, the first firing (between 1,000°C and 1,050°C) gives a piece known as ‘biscuit’ or ‘bisque’. This may then be decorated with glazes. The second firing (between 940°C and 980°C) makes the glaze coating vitrify and completes the piece’s manufacture.

CERAMICS AND INNOVATION If there is one area which focuses current attention, it’s surely that of ceramics. It is a complex field, where the materials look so much alike to the naked eye that it is difficult to identify them. The subtlety of their character­ istics makes them toys of only the experts. It’s truly the refinement of properties through ceramic techniques which makes the industrial set so passionate about them. Particularly: • Piezoelectric ceramics: Mechanical deformation makes them create an electric field and vice-versa. These ceramics are highly used in applications such as tel­ephone transmitters, watch batteries, ultrasound and sonar emitters. • Shape-memory ceramics: Providing small deformations but high forces. • Bio-ceramics: Of particular use in the field of med­ icine, growing bone tissues colonise these macropo­rous bio-compatible ceramics. The ceramic then disappears and gets reabsorbed, once the bone has ‘taken up its post’!

technical ceramics Care given to the choice of materials, their mixture and the firing temperatures used greatly improves the ceramic’s performance. In this family of technical ceramics, distinction should be made between alumina (aluminium oxide), which is able to resist wear and tear very well and yet is still quite affordable in price; zirconia (zirconium dioxide) which is resistant to friction and wear and has good thermal insulation properties; and silica carbonate or silica nitrate, which both have good mechanical and thermal properties. In certain cases, these ‘technical’ ceramics meet require­ments which neither metals nor polymers can fulfil. Refractory, with high melting points (some­times greater than 2,000°C), being either electrically insulat­ ing or semi-conductive, corrosion, wear and compression resistant, light, etc. they have made their niche in several high-tech sectors. They are used in mechan­ ics, electro-technology, surgery, optics, the nuclear industry, filtration, abrasive cutting tools, electronics, cement furnaces, ceramic matrix composite materials, glassmaking, steel manufacture.

62

List of materials examined in part 02: Ceramic, Architectural p.136

/ Ceramic, Technical p.137 / Ceramic, Traditional p.138.

List of processes examined in part 03: Assembly ding

p.278

/ Calendering

Digital processes p.304

p.316

p.302

/ Cast moulding

/ Extrusion

p.308

p.298

/ Finishes

/ Machining p.268 / Printing p.320 / Sintering p.296.

p.272

/ Bon-

/ Cutting p.324

p.260

/

/ Injection

Plas­tics Plastic: always first-generation The widespread appearance of plastics in the Nineteen Fifties, rocked the world of materials, setting them apart in a league of their own. Plastic, originally an adjective made noun. An uncertain term, refers to a plasticity that this material does not possess, at least, not in its appearance. The chemists and the professionals, however, prefer to call it a ‘polymer’. Unlike wood and metal that can be understood more empirically or in terms of technical intervention, polymers are primarily defined in terms of their chemistry – mainly the chemistry of carbon. With them, man affects the very essence of the material, perceiving his relationship with Nature and God differently. Long ago, alchemists burned more than their fingers attempting to ‘manufacture’ matter. These ‘manipulations’, devised to reveal a wide range of properties, otherwise strengthen the common perception of artificiality associated with plastics. Similarly, the immediate industrialisation of these polymorphous materials, that bypassed any maturing influence of the craftsman, is an important contributory factor to their marginalisation. Free from any ancestral tradition, the emergence of plastics was swift by a process of ‘substitution’, during the two Great World Wars. A practical replacement, It played a strong, utilitarian role but one, which without doubt was to boost its image of being a sub-material. It found its niche by a process of ‘imitation’. A chameleon material mimicking all other materials: from false wood to false skin or stone. Plastics intervene as essential but distinct agents between two materials: joints providing a watertight seal or expansion; adhesives for assembling, endless packaging. Even the walls are covered with it: paint. However, this opportunism has certainly not contributed to elevating the status of plastics to that of a noble material, in fact the immediate industrialisation of these polymorphous materials – that bypassed the maturing influence of the craftsman – is certainly a contributory factor to their marginalisation. A material which could actually be the most symbolic in our industrial society, or at least, in our consum­er society, plastic is now suffering a real identity crisis – is it a question of time or its intrinsic nature? The concepts of waste and recycling, where thermoplastics specifically demonstrate their efficiency and production flexibility, seem to integrate seamlessly with an economy continuously in need of further renewal. The plastic object is always brand new, regardless of design. If there are dimensional and structural limits (no plastic architecture, for example), then polymers cover the entire field of material states: from the hard to the soft. Steadfastly modern, they play their part in the emergence of thousands of new hybrid materials thrusting an abundant selection upon us. They overturn the very design of objects. Today, a designer can think about ‘function’ before thinking about ‘material’ and it is this plasticity of polymers that makes it possible to modify the material to fit the function. It is symptomatic that polymers assume a leading position throughout the emergence of so-called intelligent materials and nanotechnologies. It is probably here, that their true identity comes to the fore. Revolutionaries, in the Copernican sense mimicking the word, they displace centres of gravity and categories, which up to that point had served to help us to understand matter.

65

CHEMISTRY In order to understand the great properties of plastic materials, we need to examine some basic principles of chemistry. Plastics are materials made up of a set of macromol­ ecules (long molecular chains), whose central atom is nearly always carbon (apart from some instances such as silicones where the silicon replaces carbon, for example). The hydrogen atoms complete the basic molecular structure, which then, depending on the material in question, accommodates oxygen, nitrogen, chlorine, or fluorine atoms, etc. The components needed to manufacture plastics are extracted from a variety of natural substances, mainly from petroleum, but also from natural gas, from coal or from other mineral and organic materials such as sea salt, limestone, water or wood.

POLYMERS

 1

Plastic materials are sometimes obtained by means of a simple chemical alteration of a natural ‘plastic’. But generally, in order to synthesise plastic materials and by obtain macromolecules, mon­o­mers are to there­ used, small molecules where carbon atoms have cre­ ated twin bonds. These monomers then undergo a polymerisation reaction (polyaddition or poly­­­­conden­sation), which bond them together mainly by means of covalent links (simple links, result­ing from ‘opening’ carbon-carbon twin links). These covalent links, the principle of exchang­ ing electrons between carbon atoms, are strong and constitute the fabric of the long chains of monomers assembled in this way: macromolecules. Here are some basic monomers, manufactured by the chemical industry: styrene, propylene, ethylene, which, once polymerised, will produce polystyrene, polypropylene, polyethylene macromolecules.

Van der Waals forces. These links disappear when heated, allowing macromolecules to slide amongst one another and then reappear when cooled. This material is referred to as a ‘thermoplastic’. Thermoplastics soften when heated and harden when cooled. A behaviour similar to that of butter or chocolate. Demonstrating reversible processing properties under the action of heat, they have a high degree of flexibility to transform themselves, making them easy to recycle. Current thermoplastics represent 83% of the production of ‘plastic’ objects. The appearing/disappearing act of the Van der Waals links completely defines plastic as a material. Indeed the overwhelming interest in thermoplastic polymers, the many promises of form and appearance that they are able to offer and their ability to be recycled are all attributed to their transformation reversibility. Current thermoplastic polymers: polystyrene, polyeth­ ylene, polypropylene, polycarbonate, saturated polyesters, polymethylmethacrylate, poly vinyl chloride. • Thermosets: Long chains of molecules interlinked by means of strong covalent links, that the action of heat does not break (other than at the point of complete destruction of the material). This material is referred to as a ‘thermosetting plastic’. Thermosets harden through the action of heat, similar to the process of curing. Demonstrating a behaviour sim­­ilar to that of cake mixture. Processing is irreversible once subjected to heat and catalysts and is therefore a more delicate and longer process. Direct recycling is not possible. Thermosets generally have mechanic­al, thermal and structural properties that are superior to those of thermoplastics. However, they ultim­ately remain materials ‘like any other’ – still offering a high-performance weight / mechanical strength ratio. All the unpublished ‘plastic’ properties and characteristics of thermoplastics are lost. Current thermosetting polymers: polyurethane, epoxy, unsaturated polyesters.

 3

AMORPHOUS AND CRYSTALLINE Plastic materials, synthetic materials, are therefore more accurately referred to as polymers, a set of macromolecules resulting from the transformation of monomers.

THERMOPLASTICS AND THERMOSETTING PLASTICS (THERMOSETS) There are two broad types of ‘plastics: • Thermoplastics: Long chains of molecules weakly interlinked by the intermolecular links referred to as

66

The organisation of macromolecules can also assume two different forms: • Either long chains of molecules completely entangled, irregularly, regardless of the nature of the links that bond them (Van der Waals or covalent). This is the material’s amorphous state and only this is able to produce a transparent material. • Or long chains of molecules properly aligned, regard­ less of the nature of the links that bond them (Van der Waals or covalent). This is the material’s crystalline or

 2

 1

1

2

POLYMERISATION 1 monomer 2 polymer (macromolecular chains)

 2

semi-crystalline structure

amorphous structure TWO TYPES OF ORGANISATION OF POLYMER CHAINS

 3

1

strong links (covalent)

2

weak links (Van der Waals) COMPARATIVE STRUCTURES OF THERMOPLASTIC AND THERMOSETTING MATERIALS

67

semi-crystalline state. Materials that have this structure have chemical and mechanical properties that are often greater than amorphous ones and remain opaque.

Fire retardants Antioxidants • Fungicides •

•

ELASTOMERS COPOLYMERS Nowadays there is a general tendency towards having ‘alloys’. The main objective is to unify the positive prop­ erties without combining the bad ones. The mixture is not intimate, it is more of a co-existence. Polymers are no exception to the rule, which is why we are witnessing an increase in the number of copoly­ mers. A current famous examples is ABS, Acrylo­ nitrile-Butadiene-Styrene, used for interior automotive components such as dashboards or door handles and mobile phone and vacuum cleaner bodies. The copolymer Polypropylene – Polyamide (PP-PA) is also widely used in the field of automotive manufacturing for rearview mirrors and bodywork parts.

ADDITIVES AND AGENTS Rarely used in their pure form, polymers are increasing­ ly formulated depending on the end use of the objects (chemical strength, impact-resistant). They are manip­ ulated, within the limits of their compatibility, either by combining them (to obtain copolymers) or by adding various elements to them in order to enhance their prop­erties. These elements are called additives (when they represent more than 10% of the weight of the finished product) or agents (when they represent less than 10% of the weight of the finished product). The following are examples of additives: Plasticisers: To make the material more flexible. • Fillers: To save on the plastic material and to mini­ mise shrinkage, often chemically inert materials are added, such as sawdust, talc or carbon black. • Stiffening agents: To structure the material, to increase its mechanical behaviour and to limit shrinkage, short fibres (0.1 to 0.5mm long) are added such as glass fibre, carbon fibre or aramid fibre. • Expanding agents: For making foams.

Elastomers constitute a family of polymers with properties of enhanced elasticity, we even talk about ‘hyper­ elasticity’. In effect, these materials are able to stretch 5 to 10 times their initial length without breaking and return to their original shape after stretching. It is therefore sensible to make a distinction between the concepts of ‘elasticity’ and ‘plasticity’, which can be differentiated by their ability or inability to return to the initial shape of the material after stretching. Natural rubber (NR) or latex, collected in rubber tree plantations, is the oldest and the most typical elastomer. Synthetic rubber also exists. Elastomers include: some silicones, some polyurethanes, Neoprene (trademark registered by Dupont de Nemours for the first synthetic elastomer: polychloroprene), EPDMs (ethylene propylene diene monomers). Paradoxically, most elastomers are thermosetting polymers, so processing them is complex and recycling them is difficult. TPEs (thermoplastic elastomers) have recently ap­ peared, which can easily be injected and are gradually replacing rubber in some applications. The glue sticks for hot glue guns, for example, are made of TPE. Unfortunately, for the time being they have fairly low temperature resistance (less than 100°C), which does represent an obstacle to their progress. Worthy of note are styrene-based TPEs (SEBS), olefin-based TPOs and polyurethane-based TPUs.

•

The following are examples of agents: Colorants and pigments (note: a colorant is able to dissolve in the material, giving it a transparent color. Impressive transparent effects can not be achieved using pigments as they remain dispersed in the material.) • Lubricants • Anti-static agents • Anti-UV agents

CLASSIC POLYMERS / APPLICATIONS AND PROPERTIES Thermoplastics constitute the overwhelming majority of polymers used today. To identify them in terms of recycling, an international standard classifies them into 7 families. Most requirements are met by the first six polymers, that can be identified by the following markings:

•

68

1. 2. 3. 4.

PET, polyethylene terephtalate PEHD, high-density polyethylene PVC, poly vinyl chloride PEBD, low-density polyethylene

 4 sport and leisure (5%)

furnishings / bedding (3%)

electricity and electronics (7%)

medical (1%) various (8%)

transport (14%)

building and public works (22%)

packaging (40%)

Standard

Use with food

Transparency

Appearance

Use with adhesives

Chemical resistance

UV resistance

Heat resistance

Fire resistance

Abrasion resistance

Impact resistance

MAJOR SECTORS OF POLYMER APPLICATIONS

PS PEBD-PEHD

PVC

*

ABS PET TPE PP PMMA PA PC

*

POM PU UP High performance
5,500 K), the ‘colder’ the light is (rich in blue, closer to daylight). The lower it is (< 3,300 K), the ‘warmer’ the tones are (rich in red and yellow). For example, a classic incandescent lamp has a colour temperature of 2,700 K, or a warm colour, the same as for halogen lamps. In contrast, a ‘daylight’ fluorescent tube is cold in colour, with a temperature of 6,000 K. Colour rendering index The acronym for the colour rendering index is CRI or Ra. It is the capacity of a light source to render the colours of the object that it is illuminating. Values range from 50, ‘bad’ to 100, ‘very good’. Below 50, the CRI fails to render anything. The CRI of incandescent sources is generally 100, some fluorescent tubes, however, can reach an CRI of up to 66, which does not make easy viewing. The sodium light sources of a tunnel (having a CRI of 25) completely modify, for instance, our perception of the colour of objects.

 2

 1 400 nm

ultraviolet

violet

700 nm

VISIBLE LIGHT

blue

green

yellow

orange

red

infrared

LIGHT SPECTRUM

Power (W)

Luminous efficiency (lm/W)

Colour temperature (K)

Average life (h)

Colour Rendition Index (CRI)

 2

Standard

15 - 1 000

8 - 18

2 600 - 2 900

1 000

100

LV halogen

50 - 2 000

13 - 20

3 000

2 000

100

ELV halogen

15 - 100

16 - 22

3 000

2 000 - 4 000

100

Metal halide

50 - 2 000

70 - 100

3 000 - 6 000

6 000 - 8 000

65 - 85

High-pressure sodium

35 - 1 000

50 - 150

2 000 - 2 500

8 000 - 24 000

80

Tubes

18 - 36 - 58

60 - 100

2 700 - 6 500

8 000 - 12 000

66 - 98

Substitution lamps

5 - 23

40 - 60

2 700 - 3 000

8 000

85

INCANDESCENCE

DISCHARGE

FLUORESCENT

Integrated lamps

5 - 55

80 - 95

2 700 - 4 000

8 000 - 12 000

85

led

1-3

12 - 60

60 - 90

50 000 - 100 000

75 - 80

COMPARATIVE TABLE OF DIFFERENT LIGHT SOURCES

 3

DISCHARGE mercury sodium fluorescence (tubes, compacts) INCANDESCENCE standard halogen optical fibre LED

electroluminescence phospho / fluo

SOURCES

109

1

2

3

4

5

6

7

8

9

10

11

12

13

LAMP SHAPES INCANDESCENT LAMPS: 1 standard 2 / 3 with internal reflector 4 fantasy 5 low voltage twin-cap tungsten-halogen 6 / 7 double-envelope

low voltage tungsten-halogen 8 extra-low voltage tungsten-halogen with dichroic reflector 9 miniature ELV tungsten-halogen DISCHARGE LAMPS: 10 metal halide 11 high-pressure sodium tube 12 high-pressure ‘white-light’ sodium 13 high-pressure mercury vapour

110

 4

1

2

3

4

7

8

5

9

6

10

11

12

13

14

LAMP SHAPES DISCHAGE LAMPS (FLUORESCENT): 1 to 8 compact substitution fluorescent 9 special integrated compact fluorescent lamps without

integral starter 10 special integrated compact fluorescent lamps with integral starter 11 standard fluorescent tube 12 / 13 integrated compact fluorescent lamps 14 circular fluorescent tube

111

LIGHT AND INNOVATION Today, controlling light phenomena is dependent upon the ability to resolve energy issues and the ability to produce this energy. Issues relating to safety, endur­ ance, in particular (electricity involves a physical connection), power consumption (energy savings) are all good reasons for research and innovation. Other than optimising existing sources – LEDs, which are becom­ ing light sources in their own right and the OLEDs (Organ­ic Light-Emitting Diodes, both light sources or displays, gradually replacing liquid crystal displays) – the spotlight is set on the following areas: • ELV (Extra-Low Voltage) or ULV (Ultra-Low Voltage) addressing safety and energy-saving issues, amongst other things. • Delocalisation of the electric source, made possible, for example, using fibre optics. You can submerge fibres in water without danger. Lighting equipment and water have never made good companions up to now. • Batteries are becoming more and more high-performance ensuring increased endurance. • Induction-fed light sources.

List of materials examined in part 02: Electroluminescence p.147 /

Fibres, glass

p.153

discharge fluorescent p.182 /

/ Laser

p.181

/ Led

p.179

/ Light source,

/ Light source, halogen incandescent

Light source, sodium, mercury discharge p.183 / Light source,

standard incandescent

p.184

p.203 / XX-Chromatic p.251.

112

p.176

/ Phosphorescence – Fluorescence

114

2

3

4

5

6

7

L

M

N

O

P

Q

K

Yttrium

Y

Barium

Ba

Lanthanoids

—

Radium

Ra

Actinoids

—

(M) 88 (TG) 89-103

Fr

Francium

87

Caesium

Scandium

Sc

(M) 57-71

Sr

Strontium

(M) 56

Cs

55

Rubidium

Rhodium

Rh

45 (TM) M = metals TM = transition metals NM = nonmetals RE = rare earths NG = noble gases AG = all groups

Titanium

Ti

Vanadium

V Chromium

Cr Manganese

Mn Iron

Fe Cobalt

Co Nickel

Ni Copper

Cu

Tantalum

Ta

Tungsten

W

Molybdenum

Mo

Rhenium

Re

Technetium

Tc

Osmium

Os

Ruthenium

Ru

Iridium

Ir

Rhodium

Rh

Platinum

Pt

Palladium

Pd

Gold

Au

Silver

Ag

Mercury

Hg

Rutherfordium

Rf

Dubnium

Db Seaborgium

Sg Bohrium

Bh Hassium

Hs Meitnerium

Mt Ununnilium

Uun Unununium

Uuu Ununbium

Uub

Ununtrium

Uut

113

Thallium

Ununquadium

Uuq

114

Lead

Pb

Tin

La

Ce

Cerium

Pr

Praseodymium

Nd

Neodymium

Pm

Promethium

Sm

Samarium

Eu

Europium

Gd

Gadolinium

Tb

Terbium

Dy

Dysprosium

Ho

Holmium

Er

Erbium

Tm

Thulium

Yb

Ytterbium

Lu

Lutetium

Actinium

Ac

Thorium

Th

Protactinium

Pa

Np

Neptunium

Pu

Plutonium

Am

Americium

Cm

Curium

Bk

Berkelium

Cf

Californium

Es

Einsteinium

Fm

Fermium

Md

Mendelevium

(NG)

No

Nobelium

Lr

Lawrencium

Ununpentium

Uup

115

Bismuth

Ununhexium

Uuh

116

Polonium

Po

Ununseptium

Uus

117

Astatine

At

Iodine

I

Bromine

Br

Chlorine

Cl

Fluorine

Uuo

Ununoctium

118

Radon

Rn

Xenon

Xe

Krypton

Kr

Argon

Ar

Neon

Ne

Helium

He

The periodic table of the elements is the result of research by the Russian chemist Dmitri Mendeleyev (1834-1907). It is an overview of all the fundamental chemical elements, listed by increasing atomic number (the atomic number is the number of positively-charged protons in the nucleus of an atom and so it follows that, for an atom with a neutral charge this value is also the number of negatively-charged electrons orbiting the nucleus). Some of these elements, at a normal temperature and pressure (0°C and 1 atmosphere) are in liquid form (only bromine and mercury) and the remainder exist as gases or solids. The majority of elements are metals. There are several sub-categories of metals, such as alkaline metals, the lanthanides. Metalloids are elements with properties that are a mixture of those metals and non-metals or somewhere in-between. The remainder are in categories such as non-metals, noble gases or halogens, for example.

Uranium

U

89 (RE) 90 (RE) 91 (RE) 92 (RE) 93 (RE) 94 (RE) 95 (RE) 96 (RE) 97 (RE) 98 (RE) 99 (RE) 100 (RE) 101 (RE) 102 (RE) 103 (RE)

Lanthanum

2

VIII

(NM) 10 (NG)

F

VII

(M) 85 (NM) 86 (NG)

Tellurium

(M) 84

Bi

Antimony

Te

Selenium

Se

Sulfur

S

Oxygen

(NM) 9

O

VI

(M) 52 (NM) 53 (NM) 54 (NG)

Sb

(M) 82 (MS) 83

Ti

Indium

(M) 81

Cadmium

As

Arsenic

(M) 51

Sn

Germanium

(M) 50

In

Gallium

Ga

Ge

Phosphorus

P

Nitrogen

(NM) 8

N

V

(M) 32 (NM) 33 (NM) 34 (NM) 35 (NM) 36 (NG)

Silicon

Si

Carbon

(NM) 7

C

IV

(M) 14 (NM) 15 (NM) 16 (NM) 17 (NM) 18 (GN)

Al

Aluminium

(M) 49

Cd

104 (TM) 105 (TM) 106 (TM) 107 (TM) 108 (TM) 109 (TM) 110 (TM) 111 (TM) 112

Hafnium

Hf

Niobium

Nb

72 (TM) 73 (TM) 74 (TM) 75 (TM) 76 (TM) 77 (TM) 78 (TM) 79 (TM) 80

Zirconium

Zr

Zinc

(NM) 6

B

III

Boron

13

5

(M) 31

Zn

(M) 39 (TM) 40 (TM) 41 (TM) 42 (TM) 43 (TM) 44 (TM) 45 (TM) 46 (TM) 47 (TM) 48

Calcium

Ca

(M) 38

Rb

37

Symbol

Atomic number

(M) 21 (TM) 22 (TM) 23 (TM) 24 (TM) 25 (TM) 26 (TM) 27 (TM) 28 (TM) 29 (TM) 30

Magnesium

(M) 20

Potassium

19

Sodium

(M)

Mg

(M) 12

Na

(M)

Be

Beryllium

(M) 4

Li

Lithium

11

3

II

PERIODIC TABLE OF THE ELEMENTS

Actinoids

H

Hydrogen

1

I

57 (RE) 58 (RE) 59 (RE) 60 (RE) 61 (RE) 62 (RE) 63 (RE) 64 (RE) 65 (RE) 66 (RE) 67 (RE) 68 (RE) 69 (RE) 70 (RE) 71 (RE)

1

K

Lanthanoids

Period

Group

115

02 material CATALOGUE

ACRYLONITRILE BUTADIENE STYRENE p.119 / AEROGELS p.120 / ALUCOBOND® p.121 / ALUMINIUM p.122 / ASPHALT p.123 / BASALT, MELTED AND LAVA p.124 / BAKELITE p.125 / BAMBOO p.126 / BIOPOLYMERS p.127  / BRASS p.129  / BRONZE p.130  / BURRS p.131  / CARBON p.132  / CARDBOARD p.133  / CAST IRON p.134  / CELLULOSE ACETATE p.135  / CERAMIC, ARCHITECTURAL p.136  / CERAMIC, TECHNICAL p.137  / CERAMIC, TRADITIONAL p.138 / CHIPBOARD p.139 / CONCRETES, CONVENTIONAL p.140 / CONCRETES, FIBRE p.141  / CONCRETES, HIGH PERFORMANCE p.142 / COPPER p.143 / CORK p.144 / CRYSTAL p.145 / DIAMOND p.146 / ELECTROLUMINESCENCE p.147 / EMERALD p.148 / EPOXY OR EPOXIDES POLYEPOXIDES p.149 / FELT p.150  / FIBRES, ARTIFICIAL p.151 / FIBRES, CARBON, ARAMID, BASALT p.152 / FIBRES, GLASS p.153 / FIBRES OF ANIMAL ORIGIN p.154 / FIBRES OF VEGETABLE ORIGIN p.155 / FIBRES, SYNTHETIC p.157 / FOAMS p.158 / FULL GRAIN LEATHER p.159 / FUR p.160 / GALLIUM p.161 / GLASS, 3D p.162 / GLASS, BOROSILICATE p.163 / GLASS, COATED p.164 / GLASS, SECURITY – SAFETY p.165 / GLASS, TOUGHENED p.166 / GLASS, VITROCERAMIC p.167  / GOLD p.168  / GRANITE p.169  / HONEYCOMBS p.170  / HORN p.171  / IVORY p.172  / LACQUER p.173  / LAMINATED TIMBER, GLUED p.174 / LAMINATES p.175 / LASER p.176 / LATHEBOARD OR COREBOARD p.177 / LEAD p.178 / LED p.179 / LED, O-, P-, PHO- p.180 / LIGHT SOURCE, DISCHARGE FLUORESCENT p.181 / LIGHT SOURCE, HALOGEN INCANDESCENT p.182 / LIGHT SOURCE, SODIUM MERCURY DISCHARGE p.183 / LIGHT SOURCE, STANDARD INCANDESCENT p.184 / LIMESTONE p.185 / LIQUIDMETAL® p.186 / LITHIUM p.187 / MAGNESIUM p.188 / MAGNETIC MATERIALS p.189 / MARBLE p.190 / MDF p.191 / MERCURY p.192  / METAMATERIALS p.193 / MIRRORS p.194  / MORTAR p.195  / NACRE p.196  / NON-NEWTONIAN FLUIDS p.197  / NUBUCK – BUCKSKIN – SUEDE p.198 / ORIENTED STRAND-BOARD p.199 / PAPER p.200 / PARCHMENT p.202 / PHOSPHORESCENCE – FLUORESCENCE p.203  / PHOTOVOLTAIC CELL p.204  / PIEZOELECTRIC MATERIALS p.206 / PLASTER p.207 / PLYWOOD p.208 / PLYWOOD, MOULDED p.209 / POLYAMIDE p.210 / POLYCARBONATE p.211 / POLYESTER p.212 / POLYETHER ETHERKETONE p.213 / POLYETHYLENE p.214 / POLYETHYLENE TEREPHTHALATE p.215  / POLYMETHYL METHACRYLATE p.216  / POLYOXYMETHYLENE p.217  / POLYPROPYLENE p.218  / POLYSTYRENE p.219  / POLYTETRAFLUORETHYLENE p.220  / POLYURETHANE p.221  / POLYVINYL CHLORIDE p.222 / PRECIOUS STONES p.223 / RARE EARTHS p.224 / RUBBER – LATEX p.225 / RUBY & SAPPHIRE p.226 / SANDSTONE p.227 / SCHIST p.228 / SEMICONDUCTORS p.229 / SHAPE MEMORY ALLOYS p.230 / SHARKSKIN OR SHAGREEN p.231 / SHELL p.232 / SILICON p.233 / SILICONE p.234 / SILVER p.235 / SOLID SURFACES p.236 / SUPERCONDUCTORS p.237 / STAINLESS STEEL p.238 / STEELS p.239 / THERMOPLASTIC ELASTOMERS p.240 / TIN p.241 / TITANIUM p.242 / VENEER p.243 / WOOD POLYMERS p.244 / WOOD, RETIFIED p.245 / WOOD SPECIES p.246 / XX-CHROMATIC p.251 / ZAMAK ALLOYS p.252 / ZINC p.253.

117

aeronautical

agriculture

building, decoration

car industry

clothing

computer science, electronics

edition

electrical appliances

electricity

fine leather goods

food safe

furniture

glasses

glue

jewellery

lighting

mechanics

medical

packaging

painting

plumbing

rail transport

sculpture

shoes

shipbuilding

signage, advertisement

sport

tableware

tools

toys

watches

waterproof

A ACRYLONITRILE BUTADIENE STYRENE (ABS)

Maximum temperature for continuous use: 80-95°C. Glass transition temperature (softening temperature): 105-115°C. ABS is a copolymer: acry­lo­nitrile butadiene styrene. It is an amorphous thermo­plastic, typically used in industry to improve the mechanical properties of standard or high-impact polystyrene (PS) to extend its applications. In comparison with PS, ABS has better resistance to heat (beyond 100°C) and better resistance to chemical agents, while being simple to put to use via all the standard plastic processing techniques (injection, extrusion and thermoforming are easy, gluing and welding are not difficult). A polymer of compromise, between strength, low cost and aesthetics, which is much in demand today, ABS has numerous applications in everyday objects. ABS polymers are suitable for indoor use but must be reinforced with anti-UV agents for outdoor use. ABS has appeared recently in transparent form. Used in cars

(dashboards, headlamp enclosures, radiator grills), the electronics industry (telephone and TV set cases, etc.), domestic electrical appliances (vacuum cleaner bodies for example), toys and office furniture.

Strong points: easily-made, can have a good finish applied, reasonable cost. Weak points: limited chemical resistance, poor resistance to UV, very low resistance to solvents.

119

A AEROGELS

Density: from 3 kg / m3 Aerogels are derived from gels in which the liquid component of the gel is replaced with air. The results are very low-density materials, with remarkable thermal insulation properties. Their development has been quite recent (in the 1930s), today, examples include aerogels of sil­ica (also called glass aerogels or glass nanogels), tin, aluminium or carbon. Aerogels based on amorphous silica are the only solid insulators with better performance than air. Comprising of 97% empty space and a little silica, their ultralight grains have truly exceptional qualities: they multiply the insulation ability of the actual products by 3 or 4 times, while transmitting light. Full transparency has not yet been attained, but for certain applications in a building, for example, it is not always required. Double windows with aerogel between the panes become inter­esting for installation in museums, hangars, roof

120

lights and screens, in particular for energy saving. In the aero­space field, silica aerogels are capable of absorbing or ‘capturing’ certain dust from comets, which damages space probes, or providing thermal protection for NASA’s astronauts or robots. Some sportswear for use in extreme climatic conditions now contains aero­ gel; such garments are light and very insulating.

Strong points: excellent thermal insulation, very good sound insulation, lets light through, long-life, not affected by moisture, stable against UV, very light. Weak points: fragility, friability, not fully transparent, delicate manu­facturing, price.

A ALUCOBOND®

Alucobond® is a trademark of the ALCAN company. It is a composite sandwich comprising of two sheets of aluminium over a polyethylene core. It offers perfect flatness with minimum weight. It is produced in different thicknesses (from 2 to 6 mm) in a continuous manufacturing process which allows panels to be cut in differing formats (widths up to 1,575 mm and maximum lengths of 8,000 mm). Weather, impact and breakage resistant, vibration and fire resistant, Alucobond® is also ex­ tremely easy to machine and use in fabrication (bending, cutting, sawing, drilling, gluing, hot-air welding, printing on it, etc. are possible). Uses of Alucobond® are diverse: exteriors, on facades, canopies, wall or interior coverings, on false ceilings, various cowlings, signs, identification/number plates, exhibition stands, furniture, etc. Many variants of Alucobond® are availample: Dibond®, the aluminium faces of able, for ex­ which are lacquered beforehand, Tecu®Bond, the faces of which are copper rather than aluminium.

Strong points: light, with very rigid, flat surface, fire-resistant, available in many standard colours, acceptable cut edge, ready to use, simple in application. Weak points: price.

121

A ALUMINIUM (Al)

Density: 2,700 kg / m3. Melting point: 660°C. Aluminium appeared at the end of the 19th century, as a rare metal in jewellery and sculptures. Owing to indus­ trialisation, it has become a commonplace metal, extensively used in industry. With competition from plastics, the only thing holding back its expansion is the high energy cost in its manufacture (but it is recyclable). Aluminium is the most abundant metal on earth, in a mineral called bauxite. It can be used practically pure (solid or in expanded form), as aluminium alloys or as an alloying element in steel, zinc, copper, titanium… It is non-magnetic and resists corrosion very well. It has good abilities as a reflector and is used in making mirrors, by deposition in a thin layer. Even if its electrical conductivity is less than that of copper, it is sometimes preferred for weight reduction. It can be welded and brazed easily.

122

Aluminium alloy (with copper, manganese, zinc, etc.) has very interesting casting properties, easy flowing and little shrinkage. It takes surface finishes very well, lacquering for example, notably for architecture, or anodising. Décor and protection of bare aluminium by anodisation (king technique) are assured by a chemical deposit of a fine layer of alumina (aluminium oxide). The major fields of application are building and décor (doors, door frames and window frames); aeronautics; food industry (aluminium film and packaging such as cans) and kitchen utensils.

Strong points: light, corrosion resistant, great aesthetic variety, recyclable. Weak points: price.

A ASPHALT

This is a portmanteau word which often refers to materials quite different from one another. The term is used in reference to pavements and roads, often instead of the correct terms such as bitumen coatings, tarmac, or concrete paving. Associated more generally with a dehumanised, urban universe. It is a material strong­ly linked to car traffic and the petroleum industry in general. And yet, asphalt is above all a material in its completely natural state, used by man since antiquity. Asphalt is a calcareous rock impregnated with a hydrocarbon (bitumen), often extracted from mines in the form of greasy powder. The combination of rock and hydrocarbon allows the creation of a material that is a little sticky, malleable and waterproof. Characteristics, which give asphalt the capacity to adapt to shapes and seal gaps, making a watertight barrier. Quite naturally, asphalt is used in building to cover terraced roofs, on old boats, where it seals the hull and on roads, where it channels the flow of water and generates little dust.

Asphalt is generally used in a partially liquefied state (by heating) so that it can be mixed with mineral aggregates, but it is also possible to simply compress the basic powder to make very dense floor tiles which are resistant to impact and chemical attack.

Strong points: sealing ability, inert to greases and hydrocarbons, malleable. Weak points: possible harmful fumes.

123

B BASALT, MELTED AND LAVA

Basalt A volcanic rock, basalt, is the result of rapid cooling magma found all over the world. It also constitutes the dark areas of the Moon. Extracted and crushed, it is re-melted at 1,300°C and poured into moulds. Slow cooling allows different shapes to be obtained: floor slabs, cobblestones, blocks and various other objects. Melted, basalt is grey anthracite in colour with a shiny iridescence giving it a metallic appearance. Very resistant to friction, chemical agents (chewing gum, ‘tags’), frost, crushing, basalt has many fields of application: town paving, internal and external paving, industry, interior architecture. Melted basalt slabs are laid in dry weather, using special adhesives and mortars. Maintenance is easy. Lava Lava is also a hard rock of volcanic origin, more or less porous and less dense than basalt. It is used directly in

124

certain regions as a construction stone or even used in an enamelled form, strong and coloured, for elements of interior (or exterior) architecture, and other purposes (kitchen work surfaces, for example). For enamelling, the rock has to be baked first (at about 1,000°C) to elim­inate any cracks, then undergo multiple enamelling passes so that the enamel can penetrate the material. In the enamelled form, the lava is resistant to frost, UV, compression, damp (it does not rot), impact, and bactericides.

Strong points: resistance, price (basalt), easy maintenance. Weak points: weight.

B BAKELITE Phenol formaldehyde resin

Bakelite is a thermosetting polymer. It is in fact a trade­ mark rather than a chemical name. Bake­lite is one of a family of phenol formaldehyde resins and is the first synthetic polymer to have emerged, in the 1900s. Named by its ‘discoverer’ Belgian chemist, Leo Baekeland. It remains one of the best thermosetting plastics but is today often replaced by other less expensive polymers. From the beginning, its electrical insulation and heat resistance properties made it very popular for telephone casings, electrical plugs and switches, gears, kitchen utensils (casserole handles), toys and jewellery. Its age is now starting to give it a certain charm with numerous Bakelite objects exhibited in ‘design’ galleries and an­ tique shops as ‘collectables’. Hard, durable, with high mechanical strength, it is still in use today in domestic electrical appliances, electron­ ics and aerospace. It used to be seen as ashtrays on café tables.This resin is formed into three-dimensional shapes by thermocompression in steel moulds.

It exists in the form of ‘Bakelised’ paper plates, Bakelite coatings were used for the first electrical and electronic circuit boards. Wood can also be ‘bakelised’. As a result it becomes a composite material with very high strength, used in mechanics (pinions, shafts, etc.) or to make high-precision models.

Strong points: electrical insulator, high heat resistance, hardness, durability, high mechanical strength. Weak points: price.

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B BamBoo

bamboo is a member of the grass family (as is wheat), which has more than 80 genres and 1,200 species. comprising of a rhizome (the underground part of the stem), a hollow stem (partitioned at the nodes) called a cane, bamboo is characterised by its rapid growth: certain species grow at more than a metre per day and can reach heights of thirty metres and diameters of 35 cm. bamboos are present naturally all over the world, except in europe. however, certain species are now cultivated in europe. they have a high strength to weight ratio, due among other things to the length of their constituent fibres, and bear comparison with highperformance composite materials. the rapid growth of this plant is useful against soil erosion. a renewable material, it is prized in the context of sustainable development. however, the ease with which it splits prevents the use of conventional mechanical assemblies. ligatures alone can be used and its uses are therefore somewhat

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limited. this type of assembly is found in scaffolding, currently made of bamboo in asia. this reaches surprising heights (up to 400 m). applications of bamboo are also found in finished products: laminates, parquet floor, veneers, weaving, which offer high resistance to abrasion and good dimensional stability. the fibres are also used for the manufacture of papers and textiles.

strong points: low weight, strength, flexibility, price, rapid growth. Weak points: easy splitting, dimensional constraints, limited assemblies.

B BioPolymers

Faced with the threat of the depletion of oil resources, researchers are looking for alternatives. today there are bioplastics, bio-sourced polymers, biopolymers, agrocomposites or agro-polymers. the meaning of these names is not always clear so care is essential when making choices. the term ‘bioplastics’ is often used for material that has an ‘organic’ end to its life as well as material whose source is ‘organic’. we consider here the terms ‘biopolymer’ and bioplastics as equivalent to a family of degradable polymers, some of which may be bio-sourced (i.e. they rely on renewable, often agricultural, resources) and others which will be derived from petrochemicals. bio-sourced polymers are not entirely new. we’ve known for a long time how to use biomass (all living matter, animal and plant) to extract latex and other plant resins or synthesize casein plastics from milk for example. polymers are intrinsically linked to carbon chemistry. this essential element can be obtained in different ways and the challenge here is to avoid oil.

in the domain of bio-sourced materials, there are two philosophies: make well-known, tried and tested polymers, e.g. polyethylene or pet (polyethylene terephthalate) for example, which maintain their characteristics when made from renewable resources. alternatively, make new types of polymers, such as those using starch, cellulose, chitin (from crab carapace), algae, etc. here again, ‘bio-sourced’ (often agro-sourced) does not necessarily mean ‘biodegradable’ and vice versa. in the domain of ‘degradable’ polymers, there are four categories: • Biodegradable: 90% of the material is broken down and the remaining 10% has no toxic effect. decomposition, aerobic or anaerobic (with or without oxygen) produces co2, water, mineral salts and other substances, creating new biomass. natural materials which have not been subjected to any chemical processing are considered as directly biodegradable. there are different types of biodegradable polymers: biomass extracts such as

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B BioPolymÈres (continued)

maize starch, potatoes, rice, cellulose, animal protein (casein, collagen, gelatin) or vegetable protein (soya), extracts from micro-organisms (bacterial polymers are obtained by fermentation); synthesised products from renewable monomers such as plas (polylactic acids) or chemically produced in the normal manner (for example aromatic copolyesters). a cautionary note is necessary however. plas, even if they are biodegradable, are now synthesized from transgenic maize. • compostable: residues from the decomposition of the material are less than 10% of the starting mass, are small and without toxic effects on the resulting compost. • Bio-fragmentable: a mixture of synthetic polymers, such as polyethylene, with vegetable or mineral elements. the natural elements disappear and the synthetic polymer is visibly broken down (but does not disintegrate). • oxo(bio)degradable: thermoplastics with additives, capable of degrading or fragmenting but their residual toxicity is not assessed and therefore not guaranteed.

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these biopolymers, wholly or partly degradable, are mainly for throwaway purposes such as in single-use packaging, bags, films. they are not (yet?) in a position to compete with the others (which can themselves be recyclable) as far as the requirements of durability and high strength are concerned.

strong points: reduction in the use of fossil resources, ideal for

packaging and agriculture. Weak points: residual toxicity, renewable resources (maize) are

thirsty for water.

B BRASS

Density: about 8,300 kg / m3. Melting point: 900-925°C. Brass is an alloy of copper and zinc, with 5 to 45% of zinc. It is yellow in colour, or gold when polished (a very fine polished surface can be obtained). Brass has mod­est mechanical properties, but is excellent for machin­ing. This allows accurate production of small parts by turning (‘bar turning’), die moulding or stamping. It is easy to braze with silver (arc and blowtorch welding to be avoided). It frequently lends itself remarkably well to surface treatments and coatings (varnish, nickel plating, chrome plating, etc.). Brass is often used (in founding) for the fabrication of objects with small dimensions, that require high precision. The main applications of brass are in ship building and electrical construction (plug and socket parts), in plumbing fixtures (ensures the correct watertightness),

general furnishing and building hardware, as well as some objects where gold imitation is desired. Simple brass (copper plus zinc) can have lead added (1 to 3%, for example) to make it easier to machine or tin, aluminium, arsenic, or iron to improve its mechan­ ical properties.

Strong points: easy to machine, high tolerance to surface treatments, cheaper than copper. Weak points: modest mechanical properties (good malleability).

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B BRONZE

Density: 8,400-9,200 kg / m3. Melting point: 1,250-1,300°C. Bronze is a copper alloy (more than 60%) and tin (3 to 25%). Perfected and put to use long before the appear­ ance of iron and steel, it is one of the most legendary metals in the history of metallurgy. It is a metal that is excellent for casting – the classic procedure using sand or a mould. Its pouring temperature is between 1,250 and 1,300°C. It welds and brazes well (with tin and silver) using TIG and MIG processes. Bronze has high resistance to wear and friction, as well as high resistance to corrosion, notably in contact with steel, qualities still appreciated today in mechanics. It also has good electrical conductivity. The addition of lead to bronze makes it easier to machine. Zinc is also used to improve lead’s malleability, phosphorous its mechan­ical properties, beryllium its hardness, etc.

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Bronze is an excellent material for objects of art, sculpture, bells, etc. With time, as it corrodes, it takes on a characteristic blue-green colour known as verdigris. It is still used for taps (more up-market than brass) and has for a long time been used for mechan­ical friction parts such as gears and bearings, in competition with plastics or other cheaper metal alloys.

Strong points: noble material, very suitable for casting, high resistance to wear. Weak points: heavy, expensive.

B BURRS

Burrs (or curls in the grain) are parts of the tree that are normally considered as defects to be elim­inated. For certain tree species, they are nevertheless conserved and exploited. Although very difficult to work and expensive, their aesthetic properties, their torment­ed effects, have always been and still are highly sought after in cabinet making, marquetry or the fabrication of small objects. Relatively rare materials, the presence of burrs is often an indication of luxury (car interiors, furnishings, presentation boxes and cases, for example). Imitations of the patterning of burrs are often used in the production of objects made from polymers or laminated coverings for architecture, dec­oration and furniture. Burrs are either located inside a pathological growth, which can become very large, in the trunk or taken from the base of the tree (or its stump). The growths are commonly caused by the presence of wounds (insect activity, fungal growth, etc.) but can

also be partially stimulated artificially. The outgrowths are never used as solid wood but cut as veneers, which offer a finish with a myriad of knots mingled in intermixed patterns. The commonly used tree species in this respect are: walnut (the veneer is known as burrwalnut), elm, silver birch, thuja, and maple. Burr taken from the stump is removed by half-rotary cutting, it has a marbled finish of tormented fibres. These veneers are very difficult to manage and, with numerous defects, they must have a wood filler applied at a later stage.

Strong points: appearance. Weak points: price, difficult to work with, lifetime.

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C carBon (c)

carbon has the highest sublimation point of all elements in the periodic table, ranging from ± 3,500°c to even higher for different allotropes. it is a crystalliferous element like silicon and is present in all living organisms. in its diamond form, carbon is very hard and transparent, but as graphite it is black, opaque and very friable. it is also the main constituent of coal. it is present in polymers, which are effectively based on carbon and rely on its ability to form links with other atoms. carbon in the form of nanotubes belong to the fullerene family (carbon in various geometric shapes),very rigid, very light, very hard, some even harder than diamond. nanotubes are metallic or semiconducting depending on their shape, with high electrical conductivity, high light-absorption properties (‘blacker than black’ pigments can be produced). carbon nanotubes are the subject of very active research but there are environmental and health issues associated with them. carbon is essential and some of its compounds are very well known, the infamous carbon monoxide (co, a

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colourless, odourless gas that quickly kills) and carbon dioxide (co2, produced by living things, industry, cars among others). carbon is also found in hydrocarbons (which combine hydrogen and carbon), with calcium in limestone and also in carbohydrates. its isotope carbon-14 is radioactive and is important in so-called carbon dating in various branches of science and in archaeology. Finally, carbon has recently been in the news for the discovery of graphene: a form of very thin graphite, actually a two-dimensional crystal, with very promising properties in the electronics field, among others.

strong points: depending on the form or allotrope: good electrical conductor, soft with good lubricating properties (graphite), good electrical insulator and a good conductor of heat, hard, transparent (diamond), as coal fuel, opaque, intensely black. Weak points: pollution.

C CARDBOARD

Cardboard is a heavy paper, with a grammage no less than 225 g / m2, comprising of either a homogeneous sheet of unbleached or bleached Kraft paper, or an assembly of different layers, chemical or mechanical paste, old papers, etc. Cardboards can be prepared to resist, for example, fat, moisture or oxidation and as a result have a multitude of uses. Corrugated cardboard Corrugated cardboard, a sandwich material which appeared in the middle of the 19th century, consists in general of two flat cardboard surfaces – or covers – and a core – or spacer – which is also cardboard and fluted or corrugated. It is the flutes which give the material its increased rigidity, absorbing crushing and impacts. As a general rule, the fluting is of lower grammage than that of the covers. In the field of corrugated cardboard there are many variants. One can find single-sided cor-

rugated cardboard (fluting plus a single cover), doublesided, double-double (two fluted spacers and three covers), etc. They are very important in industrial packaging and transport but also in point of sale advertising and for small furniture items. Moulded cardboard Moulded cardboard is made from recycled paper. It comes in the form of papier maché and is applied to the walls of moulds to produce packaging for eggs and other fragile objects. It resists crushing, moisture, can be coloured and printed on, is biodegradable and resistant to impact.

Strong points: price, easy use in manufacture, insulation, impact resistance. Weak points: limited life, resistance to moisture.

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C CAST IRON

Density: about 7,800 kg / m3. Melting point: 1,100-1,300°C. Cast iron is obtained in blast furnaces from iron-bear­ ing minerals and coke. Raising the temperature leads to melting and liquid iron, containing carbon and impurities drawn from the furnace. Cast iron contains between 2 and 6% of carbon. Cast irons can be classified in three major categories: • White cast iron: Essentially poured and cast, nonmachinable, very hard, very fragile, very resistant to wear, with a beautiful shiny white appearance. It is used for test pieces and artistic foundry work. • Grey cast iron: The most common, easy to machine, resistant to corrosion, capable of absorbing vibration. Grey cast iron parts do not often have the same characteristics at the surface as in the centre. Heat treatment allows hard, wear-resistant surfaces to be obtained, while conserving the general properties of elasticity and flexibility.

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Spheroidal graphite cast iron: A grey iron, obtained by the addition of 0.1% magnesium, which modifies its grain structure and improves its properties to those of steel. This type of cast iron is mainly used in mechanical items (engine blocks, brake discs, crankshafts). Cast iron production serves mainly for steel fabrication (it is then called pig iron) which, is again used in mechanics, street furniture, machine tools, building, fireplaces, stoves, etc.

•

Strong points: price, complex casting possible, great compressive strength. Weak points: weight, difficult machining, difficult welding, fragile, corrosion.

C CELLULOSE ACETATE (CA)

Maximum temperature for continuous use: 45-70°C. Glass transition temperature (softening temperature): 100-130°C Cellulose acetate is an amorphous thermoplastic, obtained by conversion of cellulose, obtained from cotton and wood. It is a plastic silky to the touch with a shiny appearance, which can be very transparent. It has good resistance to impact and scratches. This vintage plastic, losing its way a little, seems to be making a comeback for its soft tactile qualities and its suitability for decoration. Its chemical resistance is low: cellulose acetate discolours and deteriorates with a characteristic smell of acetic acid, the ‘vinegar syndrome’, as it is known. Cellulose acetate is not food compatible, very sensitive to solvents and its heat resistance is modest. Its applications include photographic films (it replaced cellulose nitrate), cellulose varnishes, screwdriver hand­ les, ball-point pen bodies, spectacle frames (imitation

tortoiseshell) and, in the form of extruded fibre, viscose or rayon textiles (so-called ‘artificial silk’), based on continuous viscose fibre. There are different variants of cellulose acetate.

Strong points: impact resistance, scratch resistance, touch, appearance, transparency, tortoiseshell imitation. Weak points: low heat resistance, poor resistance to chemical agents.

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C CERAMIC, ARCHITECTURAL

The word ceramic has many connotations. In the architectural domain, it refers to floor or wall tiles made by bak­ing natural clays. The following distinctions are made: • Earthenware tiles: The porous biscuit based on kaolin, is enamelled (opaque or transparent enamel). Earthenware tiles are quite sensitive to impacts and temperature changes. They are used inside buildings. • Fired tiles: Coloured, fired clay. Porous, frost-sensitive, quite fragile. Used for wall coverings. • Sintered fired tiles: Clay and sandstone mixed. Porous, frost-sensitive, easily scratched but sufficiently resistant to impacts for them to be used on indoor floors. • Stoneware: Called quarry tiles in the UK, quite strong. Used for ordinary work floors, for example domestic kitchens. • Ceramic tiles: Clays and feldspars mixed and vit­rified by baking. Ceramic tiles are very hard, do not scratch, are not porous, and are rustproof. Very suit-able for floors with heavy use, facades, etc. They can be enam-

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elled to give various aesthetic effects. They are made by moulding or re-pressing: pulled into shape from cut, extruded paste. • Industrial tiles: Based on clay, feldspar, schist, silica, etc. Thick and strong, they can be made to meet many requirements (for non-slip surfaces, for example).

Strong points: aesthetics, low-maintenance, strength, sealed surface. Weak points: application.

C CERAMIC, TECHNICAL

As we have seen, the term ‘ceramic’ now covers many different materials, involving varied compositions and applications. The term ‘technical ceramics’ describes a family of high performance materials, with exception­ al hardness values, yet fragile in certain conditions. A domain where there are not many standard products but where specifications dictate precise formulations, made to order. Alumina, silicon or boron carbide, bar­ ium titan­ate, aluminium nitrate, beryllium oxide, zircon oxide, etc., constituent elements in these ‘new’ materi­ als which are triggering completely new interest. These technical ceramics are found as powders and fibres for fillers and dies for composite materials; as additive elements in adhesives; for the fabrication of tools; as components for the electrical, medical, automobile or aerospace sectors, even in watch/clock making (watch cases). In general, technical ceramics, as well as their great hardness, all have resistance to wear and friction, abra-

sive abilities, resistance to high temperatures (more than 2,000°C), electrical insulation abilities, and resistance to corrosion. They can hold their place where no other material can compete and some of them even have piezo-electric qualities, shape memory abilities or a biological tolerance of our bodies: they can replace our bones and disappear when nature takes over.

Strong points: exceptional hardness, withstand high temperature, wear resistance, anti-corrosion, biocompatibility. Weak points: cost, fragility.

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C CERAMIC, TRADITIONAL

The word ceramic has many interpretations, above all referring to the baking of clay. Two major types of ceramics are distinguished, as a function of the composition of the paste and the baking temperature: • Porous ceramics: Also known as fired clays, which encompasses pottery, earthenware, bricks, etc. Enamelled earthenware is used for sanitary fittings or wall tiles; fired clays decorate gardens in the form of pots but are also used, enamelled, as decorative tableware (handmade dishes, for example). Bricks, like tiles, come in many forms and finishes: plain bricks, perforated bricks, brickettes, facing bricks, refractory bricks (resistant to high temperatures), hollow bricks, plasterwork bricks, and honeycomb bricks. Roof­ ing tiles, concave or convex pantiles, mechanical tiles. • Vitrified ceramics: These include sandstone, porcelain and chemical stoneware. The architectural domain uses these materials as tiling (wall and floor coverings) but also, for porcelain for example, with electrical ele-

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ments (insulation), doorknobs and handles and small sanitary-ware items. Sandstone (opaque, characterised by small black dots) and porcelains (white paste) are also found on our tables: plates, cups or vases, which can be transparent when the porcelain is very thin. The application of these ceramic materials is widely industrialised even if the know-how of real craftsmen survives, which often confers an incomparable cachet on ceramic objects. The tradition of ceramic artists endures.

C CHIPBOARD

Panels of particulate material, comprise of wood chips glued under high pressure. The different types of panels are distinguished by the size and shape of the particles, their density and the type of adhesive (thermosetting resins) providing their cohesion. Chipboard is essentially made from ground-up wood from sorted waste material. There are single-layer and multi-layer chipboard panels – i.e. the latter has a core of coarse wood particles and two layers of fine wood particles. They can be sold untreated, covered in the factory with a melamine surface (a surface coated with a paper veneer impregnated with thermosetting resin: the melamine), or covered afterwards with a laminate (see card p.175). Chipboard panels do not resist moisture well. There is however an approved type, the resistance of which is considerably improved. Despite their poor reputation, chipboard panels are probably the wood product which has undergone the

most significant development. Much use is made of chipboard in building, for floors, under-roof, temporary partitioning and ordinary furniture.

Strong points: homogeneous, flat surface, price. Weak points: weight, poor for screwing and nailing, poor bending resistance, abysmal damp resistance, friable edge and not very aesthetic, tool wear.

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C CONCRETES, CONVENTIONAL

Starting with cement concrete (which contains cement, ballast, water, additives and air) there are different types of ‘concrete materials’, for example: • Reinforced concrete: This refers to cement concrete’s weakness - resistant to compression but not with a very good tensile strength. When a concrete item has to undergo tensile or bending stresses (as in a bridge or beam), it is necessary to incorporate steel reinforcement (which offers tensile strength) to correct this. • Pre-stressed concrete: Used when the performance of reinforced concrete is not good enough. Following the example of a spring, the steel reinforcing compresses the concrete at rest and is capable, when stressed, of lengthening and allowing the concrete to decompress without reaching intolerable tractive strain. Distinction is made between pre-stressing by pre-tension and prestressing by post tension (the latter performs better), according to whether the tension on the reinforcing steel is activated before or after the concrete is laid.

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Cellular concrete: A light concrete, comprising of a fluid cement, fine sand and an additive such as alumin­ ium powder, which initiates a chemical ‘aerating’ reaction in contact with the lime in the cement. Providing a concrete with an ideal cellular structure for cast elements ready for use (blocks, panels for partitions, etc.) A good thermal insulator, it is easy to cut (with a simple saw) but does not resist local crushing well. • Architectonic concrete: The name for concrete used in architecture, sufficiently aesthetic to be used in facades, for example. •

Strong points: price, great freedom of form, durable, strong, applied in situ. Weak points: weight, time to fully apply.

C CONCRETES, FIBRE

The mechanical strength of cement concrete (a mixture of cement, ballast, water, additives and air) can be increased by incorporating fibres in the composition. The steel in reinforced concrete is then avoided, for example and so the application of concrete is easier. Metal fibres, glass fibres, polymer fibres, even vegetable fibres are used for reinforcement, as for any composite material. The fibres are in general short (a few cent­imetres in length) and fine (about 1-mm diameter), the interaction between these two parameters modifies the final performance of the concrete. Fibre concrete is in general less inclined to cracking (the fibres disperse in the material and give it structure), resistant to impact, fire resistant and more ductile than conventional concrete. According to the fibres used, the properties of the concrete are variable: with metal fibres, the concrete has better resistance to chemical attack, fatigue and abrasion; with polypropylene fibres, shrinkage is reduced.

There are also so-called ‘ultra performance’ fibre concretes which contain microfibres and offer better qualities. This type of concrete is used today in pre-fabricated elements and high-strength constructions. Glass-reinforced concrete is concrete reinforced with glass fibres. This is used frequently for finishing prefabricated covering elements (cladding panels, for ex­ ample).

Strong points: resistance to cracking, improved fire resistance, ease of application. Weak points: price, not easy to apply on-site.

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C CONCRETES, HIGH PERFORMANCE

Concretes, thanks to the increased mastery of their composition, become more and more efficient. Today, there are: • High performance concretes: This family of concretes offers compressive strength much greater than conventional concretes, high durability and low porosity. Their fluidity before setting facilitates laying. • Ultra high performance concretes: These materials in general comprise of cement, sand and ultrafine powder such as silica smoke-particle aggregates. Some of them also include microfibres (metal or synthetic). These concretes offer exceptional compressive strength and bend strength as well as high ductility. They are fluid and easily fill formwork, are not very porous, but very durable (capable of withstanding freez­ing, abrasion). The fineness of their grain allows very accurate and smooth surface finishes to be obtained. Plastifiers – water reducers – are often added to the mixture to accelerate setting time: a few hours (and not the regular 28

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days) are sufficient to obtain high value character­istics. These top of the range concretes are valued materials in the domain of street furniture and internal architecture. The concretes in the above photo (showing glints of optical fibres running through) have appeared recently and are very translucent.

Strong points: compressive strength, bend strength, high ductility, low porosity, durability, fineness of grain, accurate and smooth surface finishes, fluidity, easy to apply. Weak points: price.

C COPPER (Cu)

Density: 8,800-9,250 kg / cm3. Melting point: 1,083°C. Copper is probably the first metal used by man. Despite existing in its native state in the ground, nowadays (due to its low abundance) it is usually produced by converting sulphides – a relatively simple process. Brown or orange in colouring, it is used for its electrical conductivity (95% of that of silver, the most conductive metal). It also has excellent thermal conductivity and excellent resistance to corrosion (copper takes on a blue-green colour when it corrodes) and a relatively low coefficient of friction. It is very ductile, therefore easy to fabricate by plastic deformation. It is easily brazed, with silver or tin. However, in the annealed state, its properties are mediocre and can be improved by work hardening. Its main applications are: plumbing pipes and electrical wire and components (half of the world production of copper is reserved for the manufacture of electrical

conductors). It is also used in building (roof cov­erings). Copper is very often alloyed with other metals: with zinc to produce brass, nickel or aluminium for cuproaluminium alloys. As a matter of interest, copper – essential to life as a trace element – is present, for example, in the haemoglobin of Limulus (a species of arthropod, the North American horseshoe crab) for the transport of oxygen. Their blood is blue (copper oxidation). In man, iron performs this function of oxygen transportation, explaining the red colour of our blood.

Strong points: electrical conductivity, resistance to corrosion, ductility. Weak points: high price, machining difficult.

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C CORK

Cork is taken from the bark of certain species of trees, such as the cork oak. Forming a protective layer (against weather and insects, for example), it still allows the tree to breath. Cork takes a minimum of 9 years to reach a thickness which is sufficient enough to be exploited. A very old material, traces were found in ancient Egypt and Rome. Today, one of the major producers is Portugal. Unsurprisingly, one of corks biggest applications is the manufacture of stoppers for wine bottles (some singlepiece, some agglomerated pieces). A flexible material, light and water-resistant (it decomposes slowly), it is also a good thermal, sound and vibration insulator. These qualities have qualified it for applications in build­ ing, as a wall or floor insulating material. In the form of large pieces or crushed agglomerated granules (with synthetic adhesive or natural resin, or sometimes albumen – contained in blood), it is valuable – as a renewable resource – in various fields. For a long time it performed functions now taken over by plastic materials,

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such as seals or shoe soles, for example. It is still used in the composition of linoleum, but is gradually being replac­ed by polyethylene, among others, in the manufacture of bottle stoppers.

Strong points: light, antistatic, elastic, insulates against heat, sound and vibration, resistant to water, renewable, price. Weak points: long cycle to obtain it (several years), available thick­ness (a few centimetres).

C CRYSTAL

At the end of the 15th century, in the Bohemia region of Germany, the first thick, hard glasses, loaded with oxides of lead, appeared. The technique was later improved in the 17th century in England to obtain glass with a more intense brilliance and a higher refractive index. This glass is also easier to work, over a longer period of time and at lower temperatures than previously. Lead glass is called crystal if the lead oxide content exceeds 24%. Above 50% of lead oxide, it is generally called strass (imitation gemstone) and above 60% the very densest glass is obtained, for laboratory use and as a barrier to x-rays. Crystal quite obviously serves above all for decorative tableware. Limpid, resonant, it is very resistant to devitrification (irreversible opacity) and is always an ideal addition to a wedding trousseau. It is somewhat astonishing that, in the case of glass, the term ‘crystal’ is used in the opposite sense. In effect, this material is above all glass and is therefore

amorphous, that is to say, non-crystalline. The opposite, therefore, of ‘crystal’ in terms of molecular, atomic or ionic arrangement, as the ones of metals, salt, sugar or precious stones (gems), with regular and ordered structures. There is also liquid crystal, used to describe a particular state of material, between liquid and crystallised solid. The different phases of crystal liquids have, among other things, different optical behaviours which are exploited in liquid crystal displays.

Strong points: brilliant, hard, transparent. Weak points: high coefficient of expansion, fragile.

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D DiamonD

composed of pure crystallised carbon like the other forms (allotropes) of carbon, graphite and graphene, diamond is the hardest mineral of all. it has a hardness of 10, the maximum on the Mohs scale. a piece of diamond can only be scratched by another diamond. diamonds are formed at a particular combination of temperature and pressure which occurs at great depths in the earth’s mantle, promoting crystallisation of carbon to form these gemstones. they come to the surface following volcanic eruptions or erosion may carry them into alluvial sediments. Famous diamonds have been discovered in india or brazil centuries ago but now natural diamonds, transparent, translucent or opaque, mostly come from africa, russia and australia. the issues relating to control of the deposits are important, numerous conflicts being linked to them. diamonds are classified by colour (slight tints ranging from pink, cream, blue and, black to exceptional white), by purity index (impurities are classified as flaws) and

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by weight (1 carat = 0.20 g, different from the purity index used for precious metals which is also a carat). the value of a diamond will depend on various parameters and increases exponentially as a function of its size. Quite apart from jewellery, the majority of diamond applications are in industry: for cutting and machining tools, electrodes, semiconductors, in the field of optics, etc. small synthetic diamonds are widely used in industry.

strong points: transparency, brilliance, high refractive index, hardness, very good insulator, exceptional thermal conductivity, low coefficient of expansion, biocompatible, resistant to acids and bases (alkalis). Weak points: high cost, conditions for exploitation.

E electroluminescence (el)

electroluminescence (el) was developed in the 1930’s for military projects (indication systems on aircraft carriers for example) and by nasa. produced by screen printing phosphors onto a conductive substrate, an el light comprises of several elements: a polyester substrate, conductive ink, phosphors, an electrode and a protective encapsulation. the phosphor reacts to electrical current by emitting light that, although weak, is sufficient for many signalling and rear-lighting applications (display panels, telephone screens, stairway nosing, emergency exit indication, etc.). there are now flexible electroluminescent sheets as well as wires. the light emitted is generally blue. however, several colours can be obtained, either by varying the voltage and frequency of the supply, by sheathing the wires or by overlaying them with sheets containing coloured filters. properly speaking, electroluminescence is not a light ‘source’, which brings various advantages and disad-

vantages for this technology, it cannot produce a light suitable for bed time reading but it can be used to create signs that will glow brightly in the night sky. perhaps most importantly it does not cause light pollution which is becoming an increasingly essential requirement. it is also of interest to designers as light comes from these delicate films, flexible, coloured, ‘malleable’ and with programmable effects.

strong points: low electricity consumption, thin, long-life, light weight, flexibility, no heating effect. Weak points: high voltage, needs a transformer, residual noise.

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E emeralD

emerald is a silicate mineral, a variety of beryl. it’s legendary green colour is due to the presence of chromium, vanadium and sometimes iron in its composition. it is a transparent, hard stone (about 8 on the Mohs scale, in which the maximum is 10), relatively fragile (therefore difficult to cut) and resists all acids except hydrofluoric acid. colombia is by far the biggest supplier in the world. already celebrated in the ancient world, genuine emerald is rare and one of the most precious stones. the deeper green and more intense the colour, the more valuable and sought-after is the emerald. it gives its name to a specific cut: an ‘emerald-cut’ stone is rectangular with bevelled edges. among the most famous crystals there are for example the devonshire, cut out of more than 1,300 carat, and an emerald of 16,300 carat presented to the topkapi palace in istanbul. other popular stones with green reflections (among others green corundum, close to ruby and sapphire, but also jades

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and green tourmaline) can be taken for emerald. tinted cut glass can also give a good imitation. emerald is formed under very specific geological conditions in which all its components, which are not generally in the same place, actually come together. emeralds normally contain inclusions which, rather than being called ‘defects’ by vendors are called ‘gardens’, and make each stone unique. emeralds are used above all in jewellery. however, over the centuries many virtues were attributed to them: a remedy for digestive, hearing or psychiatric problems, the stone of learning and knowledge, facilitating divination, etc.

strong points: lightly dichroic green reflections, sparkle, hardness, transparency. Weak points: rarity, cost, fragility.

E EPOXY or EPOXIDES POLYEPOXIDES

These are amorphous, thermosetting polymers, in the form of liquid resins and catalysts. Polyepoxides are often found in association with fibre, glass or carbon, for instance. Characteristically they come close to unsaturated polyesters, but have markedly better performance, apart from their setting times, which are longer, a handicap for industrial use. They have good adherence to anything. They can be used alone, as embedding (potting) resins. Their transparency quality, again better than that of unsaturated polyesters, makes them popular for decorative objects. They can be put to use by pouring, impregnating, coating and in wire winding. Their limited shrinkage makes them reliable for the production of precision parts. In the form of powder, they can be moulded by compression or transfer. Their main applications are: bi-component adhesives of the Araldite® type (which are powerful enough to be used in the fabrication of aircraft fuselage assem-

blies), anti-corrosion coatings, encapsulation of electrical parts (motors, coils), high-performance composite and sandwich materials (helicopter blades, boat masts, etc.)

Strong points: excellent mechanical strength, chemical resist­ ance (to organic solvents, bases and weak acids), transparency, excellent heat resistance (up to 150-200°C), limited shrinkage in moulding. Weak points: long setting time, delicacy required during manufacturing (among other things, toxicity).

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F FELT

Felt is a non-woven fabric, made from wool fibres or hair – goat, sheep, camel – inextricably mixed with no external binder. The entanglement of the fibres is assured by the combination of their own structure (wool has fibres with scales which ensure cohesion), moisture, heat and pressure. Felt-making is a very ancient technique where the fibres and hairs are tangled under water with soap or clay. The mat of fibres obtained is trodden and pressed to ensure an overall cohesion. Once dry, the felt obtain­ ed is a solid material. It can be clipped or pumiced to give it a good surface finish. Felt can be dyed, cut and sewn easily. It is very suitable for shaping by moulding, a process used to create hats and shoes. Today, there are targeted synthetic felts which combine fibres and polymer resins (polyester, polyamide, polypropylene). All these felts can be developed to have good sound and thermal insulation properties, to absorb impacts and change from impermeability to absorption. They consequently have industrial applica-

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tions: as seals, oil or moisture absorbing el­ements, ink rollers, leather polishing and graining, lining of ironing presses, packaging, sound-proofing, chair pads, etc.

Strong points: resistant to impacts and vibration, impermeable or absorbent, sound and thermal insulator, filtering power, resist­ ance to abrasion, resistance to wear, easily moulded, elastic, recyclable (natural felts). Weak points: weight, limited cohesion.

F FIBRES, ARTIFICIAL

In the category of chemical fibres, artificial fibres (produced by chemical treatment of natural polymers – of vegetable or animal origin – such as cellulose or certain proteins) are distinguished from synthetic fibres (from polymers linked to petroleum chemistry). As far as artificial fibres are concerned, cellulose is the most common primary material, extracted from wood, to create viscose. However, there are also certain fibres derived from milk casein, from the alginic acid from algae (to produce alginate, which dissolves in hot water) and other substances contained in plants. Artificial filaments are obtained by extrusion through a spinneret, then stretched. The shape of the spinneret is variable and thus allows control of various properties such as sheen, strength, insulation and adherence abil­ ities, etc. The fibre, continuous or discontinuous, can be mixed with others, such as wool or cotton, to form yarn. As far as viscose is concerned, cellulose is almost pure, this fibre is mechanically strong, chemically resist­ant

and absorbent. It is widely used in making string, clothing, under-garments and in furnishings. Viscose is also used in the manufacture of cellophane and biocompatible filtering membranes. Many so-called ‘veget­ able’ sponges are made from viscose. Cellulose, depending on the conversion process and different additives, can also become cupro-cellulose (the cellulose will have been dissolved in ammoniacal copper hydroxide) or cellulose acetate, for example.

Strong points: vegetable or animal origin, mechanical strength and chemical resistance, adaptable properties. Weak points: a chemical preparation is required.

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F FIBRES, CARBON, ARAMID, BASALT

Carbon fibres They are obtained by heating and fusing polymer fibres (often of polyacrylonitrile) under very specific conditions (1,100 to 1,500°C). They are then more than 90% carbon and remain soft. Treated at temperatures between 2,500 and 3,000°C, they become high-performance fibres (‘high-modulus fibres’). Carbon fibres have remark­able tensile strength. Spun and then woven, they combine with matrices, epoxy for example, to form structural composites with the highest performance. Aramid fibres They can be used with temperatures of up to 180°C, are self-extinguishing and have excellent tensile strength. The low density of these fibres makes them among the lightest of the fibrous reinforcements. The trade name Kevlar® refers to a range of aramid fibres perfected by Dupont de Nemours, with unbeatable tensile strength. Their capacity for plastic deformation is high (great ex-

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tension). They are however less resistant to compression than glass fibres (poor adherence to the resin). These fibres are very difficult to cut (ceramic cutters required) and are sensitive to UV. Basalt fibres They are obtained by extrusion of molten basalt through fine spinnerets, to obtain continuous filaments. In textile form, they are more resistant to flame than glass fabric (which is pierced very quickly). They are lower in cost than others are; they are found in protective garments, however they can be an irritant in contact with skin. Heat resistant and also corrosion resistant, they are used in numerous composite materials.

F FIBRES, GLASS

Drawn at high speed, molten glass is transformed into a filament (5 to 20 micron) and is wound directly onto a spindle. The filaments are then woven, treated or cut, depending on what they are intended for. Glass powder can also be made from the fibres by cutting them. Several glass compositions can be used. In the majority of cases, glass fibre has discrete, unseen applications as reinforcement in composite elements made with a polymer resin or concrete base (GRC – glass fibre reinforced concrete). It ensures structural mechanical qualities and improved rigidity, with significant weight gains. Glass fibre weaves are called glass mat. There are many variants (thickness, unidirectional or multidirectional weaves) which provide different functions. Glass fibre is also chemically inert, impact resistant and insulating. In the case of optical glass fibre, a bar of pure silica is drawn in an oven and brought up to a temperature of

about 2,000°C. This bar is then transformed into sev­eral kilometres of fibre at a speed of a kilometre per minute. Optical fibre is used in remotely fed (light pipe) light­ ing installations and for the transmission of information (data links, telecoms, video signals, medical field, etc.). An optical fibre consists of a core and glass envelope whose indices are chosen to guide the light along the fibre. Flexible and transparent, they are perfectly capable of transmitting light. There are also poly­mer optical fibres.

Strong points: weight, structural qualities, chemically inert, isolation (optical fibre is immune to electrical interference), insulation, light transmission. Weak points: fragile.

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F FIBRES OF ANIMAL ORIGIN

Fibres of animal origin are either taken from the hair of mammals or produced naturally by insects or spiders. Sheep’s wool and silk are certainly the most well known. The wool of angora goats is used to make mohair and other wools used are those of lama, alpaca, camel and angora rabbit. Initially these hairs were used to make felt, and then they were assembled to form yarn to be woven or knitted. Silk Silk is secreted by a worm (the silk worm) whose scientific name is Bombyx mori, meaning the mulberry silk worm. Farming of these worms is called sericulture. Wound into a cocoon, the fibre is long and delicate, soft and light, the use of which has been mastered by the Chinese for thousands of years. Its strength, with respect to its thickness, is comparable to that of steel. It is quite flexible and elastic, absorbent and shiny. Representing only a small proportion of the worlds

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fibre production, it remains a deluxe and expensive product. The term ‘grege’ silk is used to designate silk freshly secreted; silk crepe for grege silk filaments twisted together (which gives characteristic woven effect), and finally wild silk (the famous Shantung silk) which comes from non-domesticated caterpillars or spiders and is woven in very small quantities. Silk can also be mixed with other fibres. It is used in lingerie and other items of clothing, trimmings and furnishing materials. Wool The term ‘wool’ in general refers to sheep fleece. Once shorn off, the wool (short or long keratin fibres) is washed, carded or combed, spun into yarn and woven or knitted. It has properties of high thermal insulation (against heat as well as cold) and absorption (capable of retaining 18% of its weight as water) and is slightly inflammable.

F FIBRES of vegetable origin

Vegetable fibres, the most important constituent element of which is cellulose, are extracted from different parts of plants: seed for cotton, fruits for kapok and coco, stems for flax, hemp, jut, etc. Cotton Cotton is an ancient crop grown in the hot humid zones of the USA, China, India and Egypt. Today, there are many species of cotton plants (small shrubs), among which produce ‘Indian’ cotton, with short and thick fibres, slightly commercially valued; ‘Egyptian’ cotton, with long, fine fibres – the best cotton in the world – as well as tradi­tional cotton, the most widespread, also known as ‘upland’ cotton. Cotton fibres are formed with the fruit, around the seed. They are gathered mechanically – or still by hand in certain plantations – and are subjected to various treatments before being spun. The history of cotton is also part of social, political and economic history, hard labour and slavery, interests and markets.

Cotton fibre’s natural colour is between white and brown, it is hollow, therefore light. Its cellulose wall guarantees that it is absorbent (therefore comfortable, easy to dye and maintain) and strong. It is also relatively elastic. Cotton production represents more than 80% of natural fibre production. Cotton growing is also synonymous with chemical pollution (pesticides, fertilisers) and genetically modified organism (GMO) trials, parameters that our era of sustainable development seeks to master. Despite news of biological cotton (without [chemical] fertiliser or pesticides) and fair trade, the majority of cottons available today are far from being that natural, and, on the contrary, make a high demand on chemical products. Flax Cultivated in temperate zones, this is also a hollow, therefore light fibre, absorbent and strong (above all, wear resistant), sound but crumples easily. Used for

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F FIBRES of vegetable origin (continued)

household linen and clothing, it can also be mixed and be found in furniture, certain technical fabrics (postal sacks and drive belts, etc.) and certain papers such as banknotes. Also, extracted from the seed is linseed oil, with siccative properties useful in paints and varnishes. Hemp Hemp fibres are also hollow and light, very strong and absorbent, but rougher to the touch than linen. Previously used for string and rope as well as in certain weaves for clothing, today hemp is used predominantly in paper making (cigarette papers, filter papers) and as a filler in thermoplastics. A hemp ‘wool’ is also used for building insulation. The cultivation of hemp, among other plants hungry for CO2 is of benefit to the planet. Other vegetable fibres are appearing in the textile field: fibres of pineapple, bamboo, algae and even fibres linked to the conversion of maize and beetroot (see

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biopolymers p.127). Certain non-woven textiles, originating from tree bark (giant African fig, among others), become wood ‘cloth’.

F FIBRES, SYNTHETIC

Synthetic fibres are chemical fibres which are distinguished from artificial fibres by their link to petroleum chemistry. As their name indicates, they are synthesised from thermoplastic polymers such as polyamides (which give Nylon®, polyamide 6-6, for example); polyesters (which give Tergal® and Dacron®, for example) or polyacrylics (which give Dralon®, for example). The fibres are obtained by extrusion through a spinneret of variable shape and then stretched. These operations are carried out using a polymer in solution or in its molten state; extrusion and stretching sometimes require a dry, gaseous atmosphere, sometimes baths of reagent or simply air (dry extrusion, via a moist channel or in its molten state). These fibres have great regularity, owing to their madeto-measure fabrication. Delicacy, lightness, rigidity, strength, thermal conductivity, extension to breaking, resistance to light can all be calibrated. In general, these fibres are rot-proof, are not very absorbent, readily take

on an electrical charge and mix well with other fibres from different origins. With the use of certain treatments, they can become crease-resistant and non-shrinking; however, originating from thermoplastics, they remain vulnerable to high temperatures. They are present in many sectors: conventional, such as clothing or furnishings (they can be glossy and highly coloured) and more specialised, such as the high performance field of so-called ‘technical textiles’ – linked to cars, sport, medicine, industrial filtration, building, civil engineering, aerospace or agriculture.

Strong points: lightness, delicacy, strength, sheen, possible col­ ouration, adaptable properties. Weak points: their origin in petroleum chemistry.

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F FOAMS

Foams – mostly polymer foams – are cellular materials which hold large quantities of air. When foamed, the lightened material becomes absorbent, shock-absorbent, and a better heat and sound insulator. Foams are frequently classified as rigid, semi-rigid and flexible. The cells are open or closed (as a result their capacity to absorb water or air varies, as well as their capacity to return to their initial shape after deformation; there are so-called ‘delayed’ or ‘memory’ foams or viscoelastic foams, which return very slowly). Foams are commercially identified by their density (in g / cm3 or kg / m3). Plastic foams are normally obtained by the expansion of a gas – liberated by a chemical process. Polyurethane foams are the most common: flexible (for mattresses, cushions, chairs) or rigid (expanded foams used for insulation in buildings). There are latex foams, at the higher end of the market but with average mechan­ical strength, which as a result need protection (a cover­ing or a polymer skin). Melamine, polystyrene,

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polypropylene, PVC, polyethylene foams, and metallic foams. Aluminium foam – very light cellular material very strong in compression – is used as the core of a sandwich materi­al or for its astonishing aesthetic aspects; copper foam for its electrical conductivity. Recycled glass foam on the other hand is used as an insulating covering material.

Strong points: light, insulating, absorbent. Weak points: lifetime (polymer foams).

F FULL GRAIN LEATHER

Full-grain leather is leather which has kept the full thick­ ness of the grain (the upper part of the dermis where, for example, the hairs are implanted). It is strong and impermeable and can take different finishes, some of which are immaculate and very smooth: • ‘Corrected-grain’ leather: The grain has been abraded to make its appearance even. There is sometimes an artificial relief pattern (grained). • Immersion-dyed leather: A leather (often lamb’s) coloured by immersion and not protected. The immersed leather is very supple and very soft, but also very fragile (and expensive). • Ooze or hazed leather: The immersed leather has received protective treatment to give resis­ tance to sunlight and bad weather while remaining supple. • Grained leather: The skin has been subjected to treatment to bring out its grain. • ‘Antiqued leather’: Sheepskin or calfskins have their pigmentation altered to obtain an aged appearance.

As any piece of leather is different from any other, leather remains an unpredictable material. The thickness of the grain depends, for example, on the animal and the tanner: for calfskin, it could be up to 0,3mm. A leather where only the grain is conserved is referred to as split leather. Noticeably of the same nature as full-grain leather, this leather is finer and more supple. The remaining part after this operation to split full-grain leather is called flesh-split leather and has numerous lower-quality applications.

Strong points: appearance, numerous finishes possible, strength, impermeability. Weak points: price, delicacy of certain finishes (liability to stain­ ing).

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F FUR

Today, 85% of fur comes from farmed animals: mink, fox, chinchilla, and rabbit. Europe supplies the greater part of it. Wild fur – muskrat, beaver, racoon or coyote – come from North America and Russia. A priori, the number of wild animals captured is regulated by quotas and only affects ‘excess’ populations. Everything is very tightly regulated, locally and internationally. However, certain species are now threatened, such as leopard, tiger, jaguar, certain zebras and must not be hunted. Poaching and clandestine trafficking cast a shadow on fur’s reputation. The fur market, kept up by trappers, was large up to the 19th century, in particular in Canada. The tradition of sales by auction continues, playing on supply and demand. Classified by colour, size, sex and quality, fur – once acquired – is worked on to make it into clothing or objects. The whole art is to arrange various pieces into a whole, to create the illusion of a single piece.

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Today, there are weaves mixing fur and other materials such as wool or lace. Fine strips of fur twisted around cotton or silk threads are also slipped into knitwear, crocheted material or clever weaves, revealing their silky hair. Synthetic fur is also very widespread. Certainly less expensive, it sometimes imitates nature to a surprising degree. False fur is fabricated by a three-dimensional weaving process, which allows the length and distribution of the ‘hairs’ to be controlled.

Strong points: insulation, touch, appearance. Weak points: price, trafficking.

G gallium (ga)

density: at 20°c, 5,900 kg/m3 in its solid form Melting point: 29.76°c

gallium is an intriguing metal which becomes liquid at a temperature of 29.76°c, literally melting in the hand. it is extracted in small traces from bauxite or zinc ore and china is the world’s main supplier today. Mendeleyev predicted its existence in his periodic table, calling it ‘eka-aluminium’. it was discovered by the French chemist lecoq de boisbaudran in 1875. its name comes from the latin gallus, which means ‘cockerel’. however, the name is usually incorrectly associated with the latin word gallia, for ‘gaul’. what’s more, this encouraged german scientist clemens winkler to choose the name germanium for the chemical element he discovered. in its pure form and as a solid it has a lovely silvery appearance and breaks easily like glass. thanks to the principle of supercooling (a precarious so-called metastable state in which matter is maintained in the liquid

phase when it would be expected to be solid at the considered temperature), gallium can remain liquid and be used for example in thermometers in place of mercury. when it solidifies, its volume increases by about 3%, just like water turning to ice and this must be taken into account for its storage. gallium is mainly used in the form of gallium arsenide, a very useful semiconductor. it is also used in medical imaging, in scintigraphy for example. it is also used in the production of very bright mirrors.

strong points: allied with another element as a semiconductor, non-toxic, shiny metallic appearance. Weak points: poor electrical conductor, breaks in its solid state, increasing volume during passage from liquid to solid.

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G GLASS, 3D

Pouring glass always poses problems with shrinkage and internal tensions which are difficult to control. There are different techniques to give shapes to glass: • Blown glass: Using a hollow blowpipe, the glass maker shapes a gob of molten glass. This is often formed into decorative coloured drinking glasses, with irregular walls and characterised by the presence of small bubbles. Stained-glass windows, dishes, bottles (industrial blowing) can all be made of blown glass; mastery of the traditional manual technique is an ancient and difficult art. • Rounded and thermoformed glass: A 3D shape is obtained from a flat sheet of glass. Vehicle wind­screens, display cabinets, spectacle lenses are made this way. • Pressed moulded glass: Molten glass is poured into a mould and heavy pressure applied via a piston. Optical lens blanks and electrical insulation elements are made this way. • Moulded glass: Molten glass is poured into a steel mould, a lost-wax mould or a sand mould. This method

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can be used to make solid glass bricks, cobbles, tiles and mosaic elements. • Sintered glass: This is made from crushed glass particles, distributed randomly, which are put in a mould and heated. It can be used to make jewellery and coloured artistic items. • Blowtorch glass: Shapes are obtained by reworking tubes or sticks of glass in the flame of a blowlamp. Vases, presentation cups or glasses can be made. Various traditional methods have also been developed for machining and finishing (including: sandblasting, bevelling, cutting, engraving) which are widely exploited today (glass jewellery, cosmetic pieces, etc.).

G GLASS, BOROSILICATE (PYREX®)

Borosilicate glass, known under the trade name Pyrex®, is capable of withstanding high temperatures (up to 400°C) and thermal stresses, owing to its low thermal expansion coefficient. It also has high resistance to chemical agents. Its exceptional properties are related to the addition of boric acid to the basic components of the glass (sand, soda, aluminium, potash and lime). Borosilicate glass is a hard glass, less dense than norm­al glass. There are items (oven dishes, plates, etc.) in borosilicate glass which can be washed in a dishwasher. A lot of glass items used in laboratories are Pyrex®, as are neon tubes, industrial pipes and columns and telescope mirrors. This type of glass is also used to permanently vitrify radioactive waste. It should be noted, that although it easily withstands a sudden rise in temperature its resistance to sudden falls in temperature are not as good, particularly when the glass is thick (taking a plate from an oven and put­ting

it in a refrigerator without having a prolonged rest­ing stage in between is to be avoided). Its use in manufacture is more difficult than tradition­al glasses, owing to its high melting point. It can be mould­ ed manually, mechanically and blown. Some items can be welded together or locally reheated for a later shape modification (laboratory beaker, for example). Parts should be reheated to eliminate residual stresses.

Strong points: resistance to high temperatures and chemical agents. Weak points: price, average optical qualities.

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G GLASS, COATED

Metal deposition Flat glass, or float glass, can be given various surface treatments for technical and/or aesthetic reasons. The term ‘coated glass’ applies above all to industrial prod­ ucts which have had a surface coating of metal oxides sprayed on in a thin layer (less than one micron). Chang­ ing the behaviour of the glass in relation to solar radiation (energy-saving and light-control, giving economic benefits as well as having an aesthetic function). By applying several layers, the treated surface can be made resistant to corrosion, abrasion, UV, scratches, some chemical agents, cleaning agents, and saline mist. The deposits are applied in a vacuum, either hot – pyro­ lysis in liquid, solid or gaseous phase – or by direct coating. With this type of deposit, various effects can be obtained: self-cleaning glass, self-heating glass, filter filtering glass and some aesthetic effects. This is also how so-called ‘one-way’ mirrors are made, for ‘seeing without being seen’.

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Enamelled or silk-screened glass Glass can also be enamelled (industrially by spray gun or brush) or silk-screened with enamel and then tough­ ened. The enamel is in fact a glass that is fusible around 600°C, loaded with pigments (metal oxides) which give it colour. There are opaque enamels and transparent enamels. Printed glass Printed glass should not be confused with coated glass. In effect, what is meant by printed glass is glass which has received a relief imprint on one of its faces during manufacture. Printed glass motifs are numerous and much valued in architecture.

G GLASS, SECURITY / SAFETY

Armoured glass When the glass is leaving the oven, as the sheet is formed and passes between the laminating rollers, a reinforcing mesh of non-oxidising metal wire is introduced to produce armoured glass. The metal mesh is held within the thickness of the glass, reinforcing its structure. This glass is found mostly in public buildings, in vertical fire-resistant partitions and in glazed walls and doors. Laminated glass Conceived to resist impacts, laminated glass comprises of a sandwich of two or more leaves of glass linked to each other at low temperature (100 to 150°C) by polymer inserts – PVB (polyvinylbutyral) or EVA (ethyl vinyl acetate). If the glass is broken, the glass splinters remain fixed to the plastics film. This characteristic is very useful for vehicle windscreens (safety glass) or anti-burglar windows (security glass), however laminated

glass also allows the inclusion of decorative films and various other material. As a result the majority of coloured glass we see on a daily basis, is laminated glass with an internal film creating its colour. Similarly, motifs, images, metal mesh, vegetable or textile material, as well as LEDs, can be integrated into the lamination. Some interleaved films can also be treated to provide UV protection or sound insulation.

Strong points: resistant to impacts, many aesthetic effects possible. Weak points: price.

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G GLASS, TOUGHENED

Performed by a heat or chemical process, glass tough­ ening compresses the external layers of the glass to improve its impact resistance. Due to the high level of compression, if the glass breaks, it does so into small, non-sharp pieces, reducing its danger. The production of toughened glass relies on certain properties of glass and in particular on the fact that it is plastic (deformable) above 550°C, elastic (rigid) below this temperature and that it expands or contracts as a function of temperature. The glass is brought up to its softening temperature (620°C), then suddenly cooled by a current of cold air. As a result, the external skin becomes rigid more rapidly than the inside. Once cooling is complete, the core will have a tendency to contract more than the skins, thus compressing the latter. Heat toughening is now applied to glass between 4 and 6 mm in thickness. It is much more complicated to perform heat toughening outside this range or on shaped pieces.

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Chemical toughening also compresses the skin of the glass, by replacing certain molecules on the surface with bigger elements, creating the same compression phenomenon. Chemical toughening gives better impact resistance, will allow work on any thicknesses and 3D shapes, but at a greater cost and gen­erally reserved for aviation, military applications and technical parts.

Strong points: large increase in impact resistance, broken glass is harmless. Weak points: slight optical deformation, risk of breaking during toughening process, impossible to cut after toughening.

G GLASS, VITRO-CERAMIC

The phenomena of expansion in glass can be significantly limited by increasing the proportion of silica or, as in borosilicate glass, by adding chemical agents which stabilise the dimensions of the glass. The same qualities can also be obtained by devitrifying the glass − partially crystallising it. Vitro-ceramic glass, was discovered in the 1950’s due to a handling error in a Corning laboratory. An oven was too hot and a block of glass was left longer than planned at a high temperature. The resultant glass was less transparent, but when inadvertently dropped on the floor, instead of breaking, just made a metallic sound. In addition to these peculiarities, this glass was insensitive to temperature, because it had a coefficient of expansion that was almost negligible. To make vitro-ceramic glass, it is necessary above all to encourage the phenomena of crystallisation in a material which has a natural tendency to solidify in a disorganised manner.

For this, the solidification temperature level is monitored carefully (ceramisation at 800°C), to allow the necessary time for the crystals to form, however, at the same time the crystallisation is limited to the minimum necessary to conserve the properties of the glass, its hardness and partly its transparency, while making them similar to those of ceramic material.

Strong points: exceptional dimensional stability and heat resis­ t­ance, mechanical strength and toughness superior to normal glass. Weak points: opaque or translucent, but never transparent.

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G GOLD (Au)

Density: 19,300 kg / m3. Melting point: 1,063°C. Gold, which can be found in its native state, as nuggets, is certainly the most symbolic precious metal, a synonym of economic value. It occupies a preponder­ ant place – the ‘gold’ effect is only obtained with gold, even in a minute amount. It is used in jewellery (about a third of world production), surface treatments (gild­ing with gold leaf down to 1 / 10,000 of a millimetre in thickness, colourings, pigments, etc.), electronics, medicine, cosmetics, food processing, nanotechnol­ogies and, obviously, stored in national banks (also about a third of production). A certified gold ingot weighs between 995g and 1,005g, its purity status must be at least 995 / 1,000 (that is, at least 995g of pure gold per 1,000g of in got). Purity is shown by a hallmark and value in carats (24 carats corresponding to 100% gold).

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Often alloyed with other metals: yellow, grey and pink gold have 75% gold, with silver and copper in varying proportions; blue gold is an alloy of iron and gold with surface heat treatment. Silver cov­ered with gold is called vermeil. Gold is readily workable cold by hammer­ing or drawing (it is very ductile) or in leaf form. Its exceptional electrical conductivity quality, among others, makes it useful for certain applications in electronics, mostly where its resistance to corrosion is useful (a thin layer on delicate contacts, for example).

Strong points: ductile, malleable, resistant to corrosion, biocompatible, excellent conductor of heat and electricity, food compatible. Weak points: rare, price, poor mechanical resistance

G GRANITE

A magmatic, plutonic acid rock with a crystalline structure, a major constituent of the earth’s crust, granite is composed above all of feldspar, micas and quartz. The mineral components are visible to the eye as the char­ acteristic grains which give granite its name. There is a great variety of granites (more than 500 colour shades listed), the most well known being black granite, flecked grey granite and pink granite. Granite polishes very well, but its granular structure does not permit fine chiselling. It is non-porous, resist­ ant to wear and its density is about 3,000 kg / m3. Granite is widely used as an interior (kitchen work surfaces) and exterior construction material; in sculpture and grave headstones. Certain gneisses (orthogneiss) – rocks also composed of quartz, feldspar and mica – come from the metamorphism of granite and are often used as construction stone. Granite is also a common term which describes any rock with a granular appearance, with qualities of im-

permeability and homogeneous structure. There is also the term ‘artificial granite’ for a concrete composed of marble ballast which, once sealed, has a surface appearance similar to real granite. ‘Belgian granite’ describes a black marble speckled with white.

Strong points: resistant to wear, impermeable, good polished surface, abundant. Weak points: granular structure which prevents fine working.

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H HONEYCOMBS

From the close observance of bees, man has used this animal cellular form as a model for the manufacture of materials, producing cellular structures of different types, which are both light and resistant to compression. These honeycomb materials, which can be aluminium, cardboard, textile, or polymer served initially as the core of composite sandwich panels. Their manufacture includes: stacking, as in a millefeuille cake, of different fine layers of material which are glued or welded to each other at certain regular locations to constitute a stretchable net forming cells (method often used for aluminium, textiles and cardboard); or a glued or weld­ ed assembly of fine polymer tubes or straws; or the controlled distribution of resin on the external surfaces of a sandwich, the detachment of the two surfaces creating a three-dimensional resin network which poly­merises and sets in cells; or extrusion. The aerospace industry, in its eternal quest for light­ ness, were among the first to exploit these cellular struc-

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tures. They are also found in the automobile industry (shock-absorption and weight saving) and in building (cellular cardboard in doors, with laminated facings, for example). Today, these materials are valued for their aesthetic appearance and their availability in a large range of colours and materials. Designers have used them to create furniture and decorative partitions, proclaiming them, curving them, backlighting them thus creating incredible light effects.

Strong points: light, resistant to compression, aesthetic. Weak points: edges difficult to manage.

H Horn

horn designates a material of animal origin – buffalo, zebra, antelope, springbok, goat, ram, chamois, etc. the majority of these horns consist of keratin (like human hair) which is also the material forming animal nails, claws or hooves. horn has long been used to make small things such as spectacle frames, knife handles, buttons, in marquetry, jewellery and combs, but was widely superseded by plastics (such as galalith in France – called erinoid in the uK) from 1900 onwards but continued to be prized and is coming back into fashion now for its ‘natural’ appearance and the artisan know-how it involves. the horn is first softened with boiling water, just as tortoiseshell is, then flattened and machined as a function of the requirement (cutting, engraving, polishing, etc.). two pieces of horn, for example tortoiseshell, can be ‘welded’ together, simply by heating them and then pressing them together. horn can also be tinted and, in essence, every item made in horn will be unique, with its own specific play of colours,

veining and translucence. like leather, this antistatic, non-allergenic material requires special care to prevent it drying out, cracking or shrinking. in this family of horn materials which are used in the same type of applications, we also find: deer antler and the bones of certain animals such as buffalo or giraffe and warthog teeth, for example.

strong points: antistatic, non-allergenic, each piece unique. Points faibles : heat-sensitive, care required, small dimensions.

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I IVORY

Ivory – or dentine – an organic material containing calcium, has always been a precious material. Bright white, it forms the teeth and the defence organs of certain animals such as elephants and other mammals including hippopotamus, walrus or warthog. Since the dawn of time, man has taken and carved ivory, transforming it into knife handles, religious objects, buttons, billiard balls, piano keys, etc. A material close to wood, ivory shows its growth by gradual concentric lines and swells in the presence of moisture. Today, its use con­ stitutes a menace for the survival of certain animal species and the sale of ivory is very regulated and even banned in certain countries. Rarity and cost mean that several ivory substitutes have appeared: fossil mammoth ivory, abundant in Siberia; vegetable ivory from tagua nut; bullock or camel bone (which have a tendency to go yellow and do not have the fine constitution of true ivory); ivorine (ivory powder with a plastics binder, in various proportions, which can

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be moulded) or finally plastics materials, which can imitate the appearance of ivory very deceptively. If, over time, ivory has a tendency to go yellow, several of grandmother’s recipes allow its whiteness to be revived: from lemon juice to milk, passing through oxygenated water or sodium bicarbonate.

Strong points: precious, symbolic, strong. Weak points: price, regulated supply, sensitivity to UV: yellows with age.

L LACQUER

Lacquer is an ancient surface coating, which is applied to various substrates: wood, bamboo, metal, leather, etc. Perfected several millennia ago in China, the lacquering technique continues to be a prized Asiatic tradition. Natural lacquering consists of the application of several, successive and very thin layers of a type of latex extracted from various trees to form a very sound and impermeable surface material. When collected, the resinous sap is very shiny and sticky. Once dry, it forms a non-porous and insoluble film. A fine lacquer has at least seven layers; for some items it can have up to 14 or 18 layers. Patience and sanding between each layer are what governs lacquering. The material can be coloured by incorporating iron oxide (to obtain black, for example), mercury sulphide (for red), arsenic sulphide (for yellow), etc, the depth and brilliance of these colours is incomparable. Industrially, the word ‘lacquer’ is used to refer to coatings painted in thick layers (acrylic, epoxy, etc.) which

are imitations of true lacquer. Shiny coatings are more resistant than matte: they are less porous. These paint coatings now offer one of the best protection for wood or metal, for example. Application is done on wellprepared substrates (sealers on wood, undercoat on metal, etc.) and is carried out by spraying and then, possibly, by baking (for epoxy powder paints).

Strong points: shine, depth, impermeable. Weak points: price, long process, impossible to repair damage.

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L LAMINATED TIMBER, GLUED

Glued laminated timber, used above all in architecture, consists of an assembly of solid wood pieces, in length and thickness, all with the grain in the same direction. Essentially resinous woods are used and, in fabrication, the gluing planes are alternated to avoid creating weakened zones. Glued laminated timber allows considerable spans to be obtained, up to 100m. Very elegant curved surfaces can also be fabricated. The strength / weight ratio of these beams is astonishing: a span of 3m supporting 20 tonnes contains about 60kg in wood, 80kg for steel and 300kg for concrete. Wood however is more bulky. This is a technique which allows all the qualities of solid wood to be preserved, while limiting the amount of offcuts and opening up dimensional possibilities. Structural framework in covered markets, swimming pools and gymnasiums, in addition to furniture (table tops, kitchen work surfaces) and bentwood furniture are among the common applications of glued laminated timber.

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Some companies are now offering standard prefabricated beams, but they can be fabricated in situ, depending on requirements. This avoids transportation problems. There are also many glued laminated timber products which use the same principle to combine wood and metal, wood and plastics, or simply several species of wood to create decorative effects. Some furniture parts can be made of glued laminated timber using production offcuts.

Strong points: large dimensions, remarkable weight and fire resistance compared to steel, dimensional stability, great flexibility in fabrication, in situ fabrication, limitation of offcuts. Weak points: durability, great thicknesses.

L LAMINATES

Laminates are high performance materials produced in thin layers and used for furniture, floor and wall coverings. Often used on wood products such as chip­board or plywood, they have a higher mechanical strength and heat resistance than chipboard panels which have a simple layer of melamine, a thermosetting polymer, applied. Laminates are made from a stack of Kraft paper sheets coated with thermosetting resin, finished on the two external faces by decorative sheets such as sheets with printed pictures, metal sheets or wood veneers. This structure is then pressed at high temperature and pressure and cut into standard formats. Laminates are in general supplied as panels. Any laminate veneer fixed to one side of a wood product with the aid of a neoprene flexible adhesive, will require the addition of a ‘counterbalancing’ laminate to balance the assembly and prevent later deformation (warping). Shapes can be made in three dimensions: cafeteria table­ tops, small items of furniture, and decorative objects.

There are numerous laminate manufacturers and an infinite number of possible combinations chosen for colour or the effects offered by the two surfaces of the material. Some imitations are quite striking (wood grain, for example). There are also close-grained, largethickness laminates which can be used for covering external facades.

Strong points: resistant to scratching, acids, heat, impact, impermeable, wide variety of decorative finishes. Weak points: difficult to use and cut.

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L LASER

The word ‘laser’ is an acronym for Light Amplification By Stimulated Emission of Radiation. This principle of stimulated emission was described by Albert Einstein in the 1920s. The laser is a source of very concentrated artificial light: perfectly regulated and coherent. All the light is emitted at a single wavelength and is not, as in other forms of natural light, a series of independent wavelengths, all out-of-phase with each other. The light from a laser is therefore monochromatic: a single wavelength at a perfectly defined frequency. There are different types of lasers, whose properties (power and emitted wavelength) vary, as well as their field of application. Lasers are distinguished by: solidstate lasers (using crystalline solid media such as glass or crystal to emit photons), gas lasers, semiconductor lasers, free electron lasers, fiber lasers, dye lasers, etc. Lasers are classified according to their danger level: class I (low power, no danger to the eye and used in

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DVD players or printers, for example) to class IV (real danger from the light, whether direct, reflected or refracted). There are lots of applications for lasers: in the lighting domain, cutting and micro-machining, micro-surgery, military, surveying (range-finders), holograms, printing, reading and recording of numerical data, telecoms...

Strong points: concentrated light beam, multiple applications, precision. Weak points: price, monochromatic, delicate manipulation, danger from some lasers.

L LATHBOARD or COREBOARD

Hybrids between plywood and glued laminated timber, lathboards have a core of soft or resinous, solid wood laths, each with more or less of a square section. This core is placed in a sandwich between one or two plies (thick veneer) which can then be covered with a thin veneer of rare wood. Care is taken to alternate the orientation of the laths, alternating the tendency of each one to deform. Thickness varies between 15 mm and 40 mm (15, 19, 22, 25 and 30 mm are the most common). Lathboard is one of the oldest wood derivates, used for a long time by cabinet makers, but has become less popular recently because of its cost. Lathboard has great longitudinal strength in the direction along the laths. However, even when covered with a decorative veneer, the presence of the laths can still be seen: there is a slight surface undulation visible. Not a good idea, for instance, to use lathboard to make a table top if you want

a nice flat varnish effect. Edges, in addition, show the laths, which doesn’t always look good. As a solution, a piece of solid wood often covers the edges. The main applications of lathboard include furniture, and shelving among other things.

Strong points: close to solid wood in use, better resistance to bending than other wood derivatives, little weight gain (not much adhesive). Weak points: average flatness, price.

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L LEAD (Pb)

Density: 11,300 kg / m3. Melting point: 327°C. Lead is a heavy, grey metal used for thousands of years. It is a mythical metal – the alchemists tried to transmute it into gold. Extracted from, among other things, galena, a mineral with a large lead content, it is rare in its native state. Lead resists corrosion and chemical agents well. Easy to melt and put to use at a low temperature, malleable and ductile at ambient temperature, this material has had many diverse applications, now becoming restricted owing to its toxicity. Used for a long time in plumbing, in paint (lead-based pigments), for munitions, roofs and gutters (replaced today by zinc in most cases), it has recently been prohibited in some countries. It can cause lead poisoning, a serious illness which affects the nervous system. In alloys, with tin and antimony, for example, lead was used in the fabrication of the first typeset characters for printing.

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Today, it is found in the form of lead compounds in ‘anti-knock’ additives in petrol for road vehicles; in sheet form as protective screens against x-rays; in pigments, in soldering alloys; some still in munitions, but above all in lead-acid batteries. These however are recycled and the lead reused. Recycled lead plays a major part in current world lead production.

Strong points: malleable, ductile, low melting point, resistant to corrosion and chemical agents. Weak points: toxicity, weight.

L LED

The light-emitting diode (LED) is a relatively recent invention. The first diode emitting light in the visible spectrum was created by Nick Holonyak in a GEC labo­ratory in New York. Small electronic components, consisting of a few millimetres, LEDs use the properties of semiconductivity. The first LEDs emitted infrared light, used for example, in remote controls (TV etc.). For a long time simple indicator lights, LEDs have now become a source of light for everyday use (torches, signalling lights, ambiance lighting in shops, car direction indicators, etc.). Their efficiency is still not high enough but continuous develop­ ment means that considerable improvement can be predicted. In the near future, LEDs could even replace incandescent lamps in the home. Their advantages could bring a genuine revolution in the lighting domain. The appearance of organic light-emitting diodes (OLEDs) promises yet more developments in the light­ing domain,

among others. Based on the same principles as LEDs, they use carbon-based semiconductors. They could soon replace liquid-crystal or plasma displays.

Strong points: very low current consumption, theoretical life unequalled (10 years continuous), maintenance almost non-existent, very low-voltage operation with almost no heating effect – therefore great safety rating, small size. Weak points: cost, true white light, difficult to obtain.

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L leD, o-,P-, PHo-

an oled is an organic electroluminescent diode, i.e. an organic led (light-emitting diode). it consists of superimposed layers of organic semiconductor materials (i.e. carbon-based), also called luminophores, connected between two electrodes. the manufacture of oleds involves the use of a vacuum deposition technique. the anode is transparent, and sometimes the cathode as well, in order to obtain a luminous surface. the first oled was produced by Kodak in 1987 and is still being further developed. oleds are already in use, mainly in display screens, where they can replace the lcd (liquid crystal) type, and in mobile telephone screens and digital camera screens. oled screens are thinner and lighter than led and lcd, can be flexible and offer darker black since no back lighting is necessary. one of the aims of research is to obtain screens with larger dimensions so that they may be used for computer and television screens and as light sources for different lighting devices.

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other technologies derived from oleds are appearing, such as pleds (polymer led), where the use of polymers, which are sometimes in liquid form, often derivatives of poly (p-phenylene vinylene) and polyfluorene between two flexible films, opens routes to faster and cheaper fabrication requiring no vacuum deposition, but instead a process rather like printing with a type of ink jet. pleds also offer the promise of low energy consumption, and screens based on pled technology will have a higher refresh rate than lcd screens. there are now pholeds (phosphorescent organic light-emitting diodes), currently the subject of research and development. these should offer higher efficiency.

strong points: flexibility, better colour rendition, good contrast, thin and lightweight display devices, cost, low energy consumption. Weak points: lifespan, small dimensions (in development), moisture-sensitive, issues concerning patents.

L ligHt source, DiscHarge Fluorescent

there are now many fluorescent light sources. the best known is, without doubt, the famous ‘neon’. these sources need an ignition device, a starter and a current limiter: the ballast. a layer of fluorescent powder is applied to the internal face of the glass envelope, which is usually in the form of a tube – the familiar long white tube. this powder is excited by invisible ultraviolet radiation which is emitted in the tube by low-pressure mercury vapour. the light emitted by the fluorescent material is visible light. the tube can also contain argon or an argon-neon mixture. More recently, a large range of fluorescent sources has been developed, integrating the starting circuit components into an almost normal-size bulb, with a base identical to the standard incandescent types so that they can be used in the same light fittings. Fluorescent lights are not as suitable for repeated on/off cycles as the standard incandescent type as they reach maximum light output after a certain delay.

Fluorescent bulbs produce much less heat than other types (above all incandescent bulbs) and are better for direct contact with all types of materials, with simple convection ventilation. allowing lamps to be made from paper or cloth. Fluorescent lighting is commonly used for work areas (offices, classrooms), commercial premises and, increasingly in the home.

strong points: long life, reduced maintenance, wide colour temperature range, low power consumption, great diversity of form, low heat output. Weak points: cost, ignition time.

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L LIGHT SOURCE, HALOGEN INCANDESCENT

Halogen light bulbs function on the same principle as standard incandescent types, but halogen (iodine and bromine) compounds are added to an inert gas enclosed in a quartz envelope. They cause a continuous cycle of chemical regeneration of the tungsten lamp filament. The temperature rise is higher, but the luminous efficiency and lifetime are increased by the continuous regeneration of the filament. It is desirable to use halogen lamps continuously to encourage this regeneration, so frequent switching on / off should be avoided. There are two types of halogen lamps: low (main supply) voltage (LV) and extra-low volt­ age (ELV), less than 50 V, normally 12 V. The maximum voltages which can be applied to the human body with­ out mortal danger are 50 V alternating current and 120 V direct current. ELV halogen lamps are therefore very safe and open the doors for accessible installations. Widely used in the commercial domain and for exhibitions, these bulbs do require special attention: venti-

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lation is essential, hence the special false-ceiling designs, for example, or choice of materials in lighting, to with­stand the high temperatures (no paper, for example, but rather ceramic or glass).

Strong points: lifetime, ELV possible, hence safety; luminous efficiency, concentrated light beam. Weak points: ELV involves the use of transformers (sometimes heavy), high temperatures, possible fire risk.

L LIGHT SOURCE, SODIUM/ MERCURY DISCHARGE

Light from discharge sources is produced by an electrical discharge in a bulb enclosing one or more metal vapours, one or more rare gases and sometimes other chemical components of varied nature. When a high enough voltage is applied, an arc is produced and the heat given off causes the vaporisation of the substances present and the progressive establishment of a stable state (ignition period). A discharge lamp using mercury vapour emits a bluish light; with sodium vapour the light is orangey yellow; with neon gas, it is red and with xenon gas it comes close to pure white. The best-known discharge lamps are sodium, mercury vapour and the fluorescent types. Unlike incandescent lights, these sources cannot be directly connected to the main supply. Various supply accessories have to be used: a ballast, a starter, etc. They have a long lifetime, but are very sensitive to volt­ age variations and their ignition time (and re-ignition) is not instantaneous.

The high light output makes these sources a good choice for exterior lighting in the public domain or, indoors, in places that are very high (for example, work­ shops) or to achieve a high light level (shop windows, large commercial premises and sports facilities).

Strong points: high light output, external use, durability. Weak points: cost, colour rendering, special treatment for recycling.

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L LIGHT SOURCE, STANDARD INCANDESCENT

The archetypal bulb: invented by Joseph Swan in 1878 and improved by Thomas Edison, comprises of a glass envelope containing a gas (often nitrogen, krypton or argon) and a tungsten filament which, when brought to a high temperature by an electric current running through it, becomes incandescent and emits light. The inert gases in the bulb limit filament oxidation. Halogen gases can be used, in which case the bulb is described as a ‘halogen’ bulb (see Light Source, halogen incan­ descent p.182). Carbon was used for the filament in the first lamp, but because it dirtied the glass envelope too quickly it was replaced by tungsten. The metal with the highest melting point (about 3,400°C), modern tungsten filaments are known as ‘coiled coil’, a form which operates at the highest possible temperature to increase the proportion of visible light for a given physical bulb size. Over time, heated tungsten sublimates and is deposited on the glass envelope and the weakened filament suddenly breaks.

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Standard incandescent bulbs, once lit, reach their maximum luminous output immediately as far as the human eye is concerned (unlike discharge lamps with are comparatively slow to light up). (See cards p.181.182). There are many forms and finishes for these bulbs, widely used for decorative lighting, lighting controlled by time switches and for rooms not often used.

Strong points: low cost, simple to use. Weak points: low efficiency (luminous output/watt), short life (approximately 1,000 hours), heat emission, safety (mains voltage).

L LIMESTONE

Present in abundance – like schists and sandstones – lime­stones are sedimentary rocks, often characterised by their white colour and the presence of fossils. Moreover, their formation is linked to the accumulation, over time, of shells, fossilised vegetation, the remains of marine animals or chemical accretions (successive deposits from rainwater, accumulated rock debris, etc.). Limestones, composed essentially of calcium carbon­ ate (calcite) or magnesium carbonate, are readily soluble in water. They are known for their effervescent reaction in contact with an acid. It’s various levels of hardness from marls (clays) to chalk and harder limestones, make the rock suitable for many uses: some limestones are widely used as dressed stone and building stone; others – in powdered form – as inert loading for plastic materials, as ballast in concretes or as flux in glass making. Lime is produced by calcinations (roasting) of lime­ stone rock. Unslaked lime, taken directly from the oven,

is a powerful desiccant: it dries up any organic material which has a high water content. It is a dangerous product which has industrial and agricultural applications. Once mixed with water, it becomes slaked lime, widely used in building to make coatings. In certain regions, water has a high content of compounds from limestone rocks the water has percolated through (so-called hard water). This has no harmful consequence for health, but the deposits cause problems for pipe work and kettles, for example.

Strong points: abundant, easy to work with, inert. Weak points: soft, poor resistance to acids.

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L LIQUIDMETAL®

LiquidMetal® is a registered name (by Liquidmetal® Techno­logies) which describes a range of revolution­ ary metal alloys: metals with an amorphous structure. These metallic glasses (which are not liquid at ambient temperature) have a particular molecular arrangement with further refinement possibilities giving them breathtaking qualities: hardness, strength, but also elasticity: they combine the properties of metals and plastics. In effect, they can be worked in a similar way to polymers: moulded, for example, they offer very precise definition of shape. They absorb vibration, resist abrasion and yet remain light. They are not subject to corrosion and are biocompatible. Their melting points are generally quite low, allowing them to be used more easily in manufacturing at less cost. Finally, according to their composition, their properties can be calibrated (as well as those mentioned above, their electrical and thermal conductivity, their resistance to wear and tear or their density, etc.can also be modified).

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The applications of LiquidMetal® are already abundant: surface treatments, military applications, electronics, the fields of medicine, sport, aerospace, watch/clock making, jewellery, etc.

Strong points: harder and stronger than titanium, higher elas­ ticity, lightness, resistance to abrasion and corrosion, biocompat­ ible, very precise shapes can be made down to details at micro­ scopic level. Weak points: price.

L litHium (li)

density: 530 kg/m3 Melting point: 180.5°c lithium is the lightest solid element known. a highly reactive, soft alkaline metal, it oxidises rapidly on contact with air, changing from silvery white to black, so it has to be submerged in mineral oil to preserve it. there is no natural occurrence of lithium in its elemental form and it is normally extracted – often as an ionic compound – from minerals such as pegmatite, loams/clays or from brines. it is also present, in extremely small quantities, in living things (from plankton to vertebrates). currently identified terrestrial reserves suitable for commercial exploitation are few. some of the larger reserves are in south america (bolivia, chile, argentina) and in china. lithium is used in the manufacture of certain glasses and refractory ceramics, in metal alloys intended for aeronautical use and in the well-known lithium batteries. despite its undeniable toxicity in some forms and under

some conditions, lithium also has various medical uses. lithium salts, among others, allow treatment of bipolar and obsessional disorders, sleeping problems and are also anti-allergenic. chlorides and bromides of lithium are used as dessicants, lithium deuteride is a fusion fuel in the h-bomb and the lithium-6 isotope is a nuclear material and a licence is required to possess it. recent developments in computing and communications technologies have generated a high demand for batteries and therefore for lithium. these are mainly rechargeable lithium-ion (commonly known as li-ion) batteries, with their high energy-density. consequently, the price of lithium has increased.

strong points: light, high electrochemical potential, therapeutic use. Weak points: very reactive (to air and water), corrodes rapidly, corrosive, toxic in some forms.

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M magnesium (mg)

density: 1,740 kg / m3 Melting point: 650°c Magnesium is among the most abundant metals on land (after aluminium and iron) and in the sea (a component part of sea salt). despite its weak mechanical properties, its very low weight (lighter than aluminium) makes it a valuable metallic material for certain specific applications, such as photo equipment cases or portable pcs. More and more applications are being found in the aerospace and automobile domains, where power consumption is related to weight. it occurs in various alloys, in particular with aluminium, for the fabrication of cans or profiles, for example. a metal with a greyish white appearance, which tarnishes very quickly in contact with air. in the form of powder or shavings, it ignites spontaneously in contact with oxygen or water. this astonishing characteristic was exploited in early photography with flashbulbs – the

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flame created gives off a lot of light – but it remains a real problem in its use, which is evidently dangerous. Magnesium is used as a reagent in the chemistry and pharmaceutical domains; magnesia (magnesium oxide) in agriculture or sport (adhesive powder for gymnastics and climbing, for example). it also plays an important part in our diet. Magnesium deficiency can be implicated in depression, cramp, etc. the magnesium content of the cocoa bean is certainly one of the good things about chocolate.

strong points: light, abundant, essential for health. Weak points: spontaneous ignition, difficult to work with.

M MAGNETIC MATERIALS

These materials exhibit the phenomenon of magnetism (permanent or reversible). This means that they exert a force of attraction on other materials such as iron or nickel. There are naturally occurring magnets – magnetite or rare earths in the Lanthanide series of elements – and artificial magnets which have been subjected to an intense magnetic field. Magnets are dipoles, characterised by a ‘north’ pole and a ‘south’ pole where the force is at a maximum. Two of the same poles on different objects repel each other, two different poles attract each other. A compass uses a magnetised ‘needle’ which invariably points to the earth’s magnetic north pole. Simple, familiar magnets are often made from oxides of iron and titanium. Their ‘power’ is variable. There are also electromagnets, which exert their force only when electrically energised. These are often used, for example in door-lock opening devices and, perhaps in the future, will provide a frictionless, levitated movement for certain means of transport.

If certain materials are ‘magnetic’, others are said to be ‘anti-magnetic’, i.e. they offer no attraction towards mag­nets. This provides a means of identification. The majority of stainless steels for example, are anti-magnetic. In the field of paints, by magnetically orienting metallic pigments, their behaviour in light is changed, allowing for example, the depth and the illusion of a third dimension to be obtained in a coating of paint.

Strong points: attractive force, flexible magnets possible, frictionless movement possible. Weak points: use of these materials is limited, difficult to machine.

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M MARBLE

Marble is a metamorphic rock, produced by marmorisation (recrystallisation of a limestone by heat to create a marble). It essentially comprises of calcium carbon­ ate, which makes it a calcareous mineral. Marbles are dense (about 2,700 kg / m3), resistant to breakage and are beautiful when polished. Veining and mottled effects are much sought after, effects mostly linked to the presence of metal oxides. There are many different marbles, depending on their place of origin and their composition. The term ‘quarry marble’ is used to refer to a calcareous stone which has characteristics close to those of marbles (hardness, density and suitability for polishing). There are white marbles (Carrara marble, for example) beige, blue, black, grey, pink, red, yellow, green and violet marbles. Marble is very often used – the term marble masonry is used to describe different techniques for use in the building domain – for floor or wall coverings. It can be used inside or outside (not every type). Some objects

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and many sculptures are creat­ed in marble. It is also used in the composition of some toothpastes. The term ‘marbling’ is also commonly used, meaning among other things the production of marble imitations. Real know-how is required to imitate the perfection of marble in stucco or painted effects, for example. In mechanical engineering, ’marble top’ is a word used to designate a perfectly flat reference surface.

Strong points: appearance, hardness, density, beautiful when polished. Weak points: price (of certain types), weight, porosity (though it can be varnished or waxed).

M MDF

MDF (Medium-density fibreboard) is produced by hotpressing a cake of wood fibres / chips. Adhesion of the fibres / chips is provided either by reactivation of the natural resin in the wood, namely lignin, or by the addition of synthetic resins. The pressure applied and the type of binder determine the panel density. MDF is a relatively homogeneous material, although more dense at the surface than at the heart. It is considered as iso­ tropic (its properties are the same in every direction). Often used for the back part of furniture, in the hidden parts of interior architecture, as panelling to be painted or covered by a wood veneer, it is also commonly used in its raw state for furniture. Very suitable for numerically controlled machining, it is used for door panels, decorative panels (cut patterns, for example) or sound insulation panels. It allows industrial production of very fine, immaculate finishes (ready for painting, for example). MDF can be self-coloured and is available in several colours.

Its good dimensional stability allows it to serve as a support for a multitude of semi-finished products: concrete panels, sub-layer for flooring (laminated parquets, for example). MDF also exists as pre-grooved panels, flexible, ideal to cover curved surfaces.

Strong points: homogeneous, flatness, price, possible fire resistance, fine finish when painted, more reliable for assemblies than chipboard. Weak points: weight, mediocre resistance to bending, poor moisture resistance.

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M mercury (Hg)

Masse volumique : 13,600 kg/m3 température de fusion : -38.8°c

a heavy metal that it is liquid at ambient temperature, mercury is most commonly found in its ore, cinnabar, which is mercury sulphide, with a colour ranging from bright scarlet to brick red. it has to be handled and stored with care, as it has neurotoxic and reprotoxic effects on all life forms. it is the subject of various legal projects aimed at reducing (or even prohibiting) its use. it vaporises and in this form is highly mobile in air, even in soil, so that its polluting effects can move around easily. by far the largest proportion of mercury emissions now come from human activities (oil refining, burning coal, incinerators, the chlorine industry, etc.). Known as ‘quicksilver’ by the alchemists, it has long been used in the form of an amalgam (an alloy of mercury with another metal). gold panning, the washing of gold particles from river sediments, allows fine flakes and dust

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to be isolated. these particles are extracted by combining them with mercury to form a mercury/gold amalgam. this is then heated and the mercury evaporates rapidly, leaving gold. the consequences are very bad for health and the environment if the operating conditions are not rigidly controlled. despite its toxicity, mercury is used in the medical field. it was the base of mercurochrome, once widely used as a topical antiseptic and now generally banned in many countries. it is still in common use as a dental amalgam. it is also found in batteries, mercury-vapour and metal halide lamps. despite the catastrophic consequences its presence may bring, it is considered as a strategic material in the field of nuclear chemistry and for some measuring instruments.

strong points: precise indicator of temperature and pressure, good electrical conductivity, chemically stable, useful alloys. Points faibles : high toxicity, heavy, evaporates very easily.

M metamaterials

the term ‘metamaterial’ now applies to several types of composite materials whose electromagnetic properties are completely new and cannot be found in ‘natural’ material. they are currently being intensively studied by scientists. some of them, in the form of layers of glass fibres in which metal rings are inserted, were made popular because of their ability, when subjected to a magnetic field, to induce an internal magnetic field which can deflect light rays in a special way. they have been found to have a negative refractive index at microwave or far infrared wavelengths of electromagnetic radiation. refraction describes the deviation of a wave (a light beam, for example) when its speed changes crossing the interface between two media. these metamaterials are being promoted as materials capable of forming a shield of invisibility, like harry potter’s famous invisibility cloak. if we’re not there yet in reality, the theoretical idea for this type of material is to make light ‘flow’ like water around a rock and in do-

ing so with a metamaterial shield, make a visible object become invisible. the size of the metamaterial components relates to the wavelengths concerned (much more work is necessary to make progress in the production of extremely small parts) and scientists have so far not managed to demonstrate the phenomenon at life-size dimensions. Metamaterials also allow astrophysicists to simulate black holes for better understanding of the physics involved. other uses are in the manufacture of ‘superlens’ antennas or perhaps one day they may even be used in floating breakwaters.

strong points: invisibility potential, negative refractive index. Weak points: life-size invisibility not yet possible, complexity in application.

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M MIRRORS

Symbolic items, mirrors offer a polished surface to reflect the image of whatever approaches them. The object of fantasy, a material of truth, narcissism and magic, a mirror offers a perfectly reversed image of real­ ity, sometimes deliberately altered (enlarging mirrors, witches’ mirrors). Certain natural situations (light on water, for example) or simply polishing a metal create a reflection, but mirrors are often comprised of a thin layer of metal (the silvering) deposited on a piece of plate glass. Historically, tin has been used (the operation of tinning), however, now it is mostly replaced by silver, sometimes aluminium. By reducing a solution of silver salts, silver is deposited on the glass. A thin protective (sacrificial) film of copper as well as varnish prevent the corrosion of the silver and guarantee resistance of the deposit to chemical or mechanical attack. Today, there are also fine polymer films – called ‘tinless’ films or spy films – carefully metalised – which create an astonishing play of reflections. These films can be

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stuck onto or laminated with the glass and allow seeing without being seen (forming a so-called ‘one-way’ mirror), reflecting light or allowing it to pass, according to the ambient light. They are used on build­ing facades and shop windows. There are also metals chemically deposited on PMMA (an acrylic) or thicker polystyrene. Which amongst other things, allows flexible and light mirrors to be ob­tained, valuable in applications where fragility and weight pose safety/security problems.

Strong points: reflection. Weak points: fragility of glass (seven years of bad luck).

M MORTAR

Mortar is a basic mixture of cement and sand. Pigments, colouring agents and various additives can be added to change its properties. Intended for finishing or assembly work such as sealing, jointing, sticking and water-proofing, mortars were traditionally prepared by masons, but are now available ready for use, formulated for particular requirements. There is a large number of mortars, with specific applications: • Adhesive mortar: Plaster based, which allows heavy parts to be fixed in place (insulation panels, tiling, marble, for example) on walls. • Anti-corrosion mortar: Resists acid attack and has applications linked to construction in the food processing industry (grain silos, for example). • Lime mortar: With lime to give some flexibility, in fitting tiles, for example. • Insulating mortar: Mix with cork, clay, as light ballast. • Building mortar: For laying breeze blocks and bricks.

Plaster mortar: For making resistant filler. Refractory mortar: For construction of ovens, boilers, etc. • Fixing mortar: Fast-setting to hold mechanical parts. • Bituminous mortar: For screeds to seal horizontal roofs, for example. • Resin mortar: The binder is resin (polyester or epoxy). Resin mortar is used for repairing or within ground coverings. • •

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N nacre

nacre, commonly known as mother-of-pearl, is a luxury biomineral material much sought after for its iridescent reflections. it comes from the internal surfaces of the shells of some bivalve molluscs such as pearl oysters, gastropods such as snails and abalone and cephalopods such as nautilus. nacre consists of alternating layers of an organic substance called conchyolin (present in small quantities and forming a matrix) and hexagonal platelets of aragonite (a form of calcium carbonate) its main component, deposited on the matrix, resulting in a very strong material. it is considered as semi-precious. its whiteness is pure and intense and the play of light on its surface is particularly appreciated. various shades are also found as a function of geographical environment and it can have a grey, green or pink tint for example. the constituents of nacre are continuously secreted by the animals, allowing damaged shell to be repaired. they make another use of nacre: an irritating foreign body such as a grain of sand can be coated with

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nacre to form a pearl, accelerated mineralisation in a living creature from an originally organic matrix. buttons, jewellery, marquetry and small precious objects are some of the main uses of this smooth, strong material, collected mainly in australia, indonesia, the philippines, Madagascar and along the coasts of india. today there are very fine products where nacre has been cut into thin slices which are then assembled and applied as a laminate to semi-rigid substrates. easy to put to use (on walls and furniture for example), these nacre products are much more affordable than ‘solid’ pieces of nacre and available in larger dimensions.

strong points: iridescent and shimmering reflections, strength. Weak points: expensive, small dimensions in original form.

N non-neWtonian FluiDs

Most fluids that we encounter, such as water or air for example, are said to behave as ‘newtonian’ fluids, i.e. their viscosity depends only on temperature and pressure. in the case of so-called ‘non-newtonian’ fluids, this viscosity is variable, as a function of the speed at which they are agitated and other factors such as time. the study of these fluids, whose behaviour cannot be explained by classical theories, is called rheology. various examples of fluids which exhibit non-newtonian behaviour are quite familiar: the behaviour of damp sand or cornflower mixed with water. these are malleable as a paste if they are stirred gently, but appear to become ‘solid’ if they are dealt with more violently. this particular fluid behaviour is the subject of advanced studies. its application for bullet-proof vests is quite promising, for example. several types of non-newtonian fluids are distinguished. the first three are those whose behaviour is independent of time, whereas the others are influenced by this variable:

pseudoplastic fluids (certain polymers in the molten state or fruit purée for example. • rare dilatant fluids (such as plastisols or honey). • viscoplastics (for example mayonnaise). • thixotropic fluids (such as yoghurts, wallpaper adhesive, some gels or moving sand). • very rare rheopectic fluids (for example chantilly cream). there are also electro-rheological and magneto-rheological fluids whose viscosity is variable under the influence of electric or magnetic fields. these are used in shockabsorbers. •

strong points: variable viscosity. Weak points: various parameters to be controlled.

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N NUBUCK, BUCKSKIN, SUEDE

Nubuck Obtained by simple smoothing of lamb, calf or buffalo skin. This treatment allows less fragile skins to be obtained, with a velvety appearance and slight sheen. Nubuck is often made impermeable, using fluorinated or siliconised resin. In general, distinction is made between: • Skipper leather: lamb, calf or buffalo skin tinted with wax, giving a marbled, two-tone appearance. • Destroy leather: goat skin tinted with wax and felted. The irregular grain of the goat skin is revealed and the upper side of the grain has a sheen. • Oiled leather: skin of calf or sheep tinted with oil. Buckskin / suede Buckskin, ‘velours’ leather, ‘suede’ leather or ‘suede’ all refer to a leather (pig, goat, etc.) with the appear­ance of velvet, obtained by smoothing the ‘wrong’ side of the skin: i.e. the flesh side of the leather. The grain therefore

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appears on the inside of buckskin objects. Better quality is obtained than with simple treatments on the outer side of the leather. Alcantara Alcantara is a coated microfibre textile, pleasant to the touch, with an appearance close to Nubuck leather. Sensitive to stains and dirt marks, it is easily washed and often used – it is finer – to imitate Nubuck. However, its ‘velours’ is of lesser quality. Alcantara and Nubuck are of similar cost. The term suedine is also used for a textile which resembles suede in appearance. Split or flesh-split leather Obtained by splitting thick leathers after tanning, split leather is a fibrous material, often reworked (buffed or ‘stoned’) to give it a velvety appearance. Not to be confused with velours leather, split velours leather is stronger, of lower quality but less expensive.

O ORIENTED-STRAND BOARD (OSB)

About twenty years ago, oriented-strand board appear­ ed, panels with large orientated particles, comprising of thin strips of wood (0.3 to 0.4 mm thick and 6 to 8 cm long). The particles are oriented in the length direction in the outer layers and in the width direction in the inner layer. The mechanical properties of these panels are similar to those of plywood. However, they are much heavier than the latter. There are different types (the number of crossed plies, sizes of particles, wood species, etc. can vary). These panels have the economic and ecological advantage that they use potentially all parts of a tree and some waste wood. Triply® is a trade name which has come into common use to refer to this type of panel. Somewhere between chipboard and plywood, it comprises of strips of wood, often pine, arranged in three crossed layers and bound together by thermosetting resins that are resistant to moisture.

OSB is used to fabricate I beams, for example, which can compete with solid wood and even metal beams. OSBs are essentially used in buildings, as floors, shuttering and packaging. Their particular aesthetic qualities have also attracted certain furniture designers.

Strong points: cost, homogeneous, mechanical strength greater than chipboard (bend resistance), moisture resistance better than chipboard. Weak points: weight, average for screwing and nailing, edges not very even, tool wear.

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P PAPER

The multitude of papers available today, and the vast fields of application, make it impossible to draw up an exhaustive inventory. Here are some examples. Papers intended for printing Between 60 and 160 g / m2 (standard ‘machine’ paper is 80 g / m2). Often called ‘laid’ or ‘vellum’ they are capable of resisting temperatures up to 180°C when being printed on or used in photocopier. The paper used in this book is a 130 g Matt Art Paper. In printing paper, distinctions can be made: • Papers with bulk: With no binder, plenty of ‘hand’, 60 to 140 g / m2, rough surface, absorbent, no printing shine, suitable for text and line drawings (paperbacks, for example). • Offset paper: With a binder to increase surface cohesion, machine-finished, calendered or dull-glazed, they can be shiny, 60 and 180 g / m2, printed by offset

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litho, in black or colours, for books, magazines, catalogues, etc. • Machine-glazed papers: One side plain and shiny, obtained by contact with a polished chrome roller. • Layered paper: Mineral surface coating on one or both sides. Different types: light layered (LWC – light­ weight coated), with a mineral coating for rotational printing, offset or gravure, catalogues and periodicals with colour pictures; modern layered with a medium coating, for offset, gravure and letterpress print­ing, or traditional layered, with increased coating, high quality surface, giving very fine printing quality. • Thin printing papers: Grammage between 22 and 65 g / m2, weight is an increasingly important issue today (effects transportation costs). These thin papers are found in publishing for voluminous works such as dictionaries, directories, religious works like the Bible, pharmaceutical instruction leaflets and household equipment booklets.

P PAPER (continued)

Newspaper and magazine papers Between 45 and 55 g / m2. Mostly made from mechanical pulps and recycled material, of mediocre whiteness, they tend to go yellow quickly. These papers however have good opacity for their fairly low grammage and high strength to with­stand the stresses of offset printing without tearing. Today, there are magazine papers of better quality than standard newspaper material. The pulp used is a mixture of mechanical pulp and chemical pulp, whitened to between 65 and 75% (ISO standard), grammage between 60 and 65 g / m2. Writing papers Exercise books, notepads, envelopes, printing paper, etc. These papers (60 to 100 g / m2) are made from chemical pulp, whitened, with mineral filler and binder. The translucence of tracing paper (30 to 110 g / m2) is due to its immersion in baths of oily resins.

Kraft papers A range of flexible packaging papers (40 to 180 g / m2), unbleached or whitened, often machine-glazed (one of the two sides is smooth and shiny). Used to pack var­ ious materials, for example in sack form, for cement, fertiliser, food, etc. Washi Japanese paper: ‘wa’ for Japan and ‘shi’ for paper. Often made from fibres from the paper mulberry tree (kozo) and hemp. Japanese papers, acclaimed for their great aesthetic qualities and strength, are often used for screens, in furniture, light fittings, packaging, origami, and kites. Household papers (toilet paper, absorbent paper, antistatic cloth, etc.); paper for banknotes or photographic paper are other materials with specific characteristics which are part of our everyday life.

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P PARCHment

Parchment is obtained by a special treatment applied to an animal skin. The first writing medium (after papyrus), parchment has been (and still is) used as the vibration surface in musical instruments, as a covering material in furniture or as a bookbinding material in art publishing. The first type of book, – comprising of leaves of parchment bound together – was called a codex. Palimpsest was the name given to a manuscript written on parchment which had already been written on and the writing rubbed off. To make parchment, the skin of goat, sheep, calf or pig, is soaked in a bath of lime, then stretched on a frame and scraped on the back to remove any flesh. It is finally polished with pum­ice and whitened with powdered chalk until it is extremely thin, in fact almost translucent. Once dried, the parchment can be waxed, given a shine, coloured or varnished. The quality of parchment (thickness, supple­ness, grain, colour, etc.) depends on the skin and the know-how of the craftsman parchment maker.

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Parchment made from the skin of stillborn calves is some of the finest and most prized and is called vellum. Skins are in general sold whole in one piece, ready to be turned into parchment, which can be glued, sewn, printed, embossed, embroidered, cut, written on by laser, etc. It can also have special surface treatments such as water-repellent dressings, for example.

Strong points: thin, transparent, supple, durable, each piece is unique. Weak points: price, difficult to process, each piece is unique.

P PHOSPHORESCENCE FLUORESCENCE

Phosphorescence Normally, when a molecule becomes excited, it becomes de-excited almost immediately. In a phosphorescent material, this de-excitation is slow: the molecule then emits light well after having received it. This property is widely exploited today, among other things to indicate certain objects in darkness, baby monitors or fish lures, etc. However, the emission of light decreases quite rap­idly (between several minutes to several hours for the most advanced applications). Fluorescence When a coloured object has light on it, it absorbs all the component colours apart from some, which it reflects. If the leaves of trees appear green to us, it is because they absorb all the colours in the incident light, except green. Illuminated with red light, they appear black, since they absorb the red light and therefore emit nothing. A fluor­ escent material emits a very precise colour and absorbs

all the other colours. It uses the light energy to emit its own colour. If a fluorescent orange material is illuminated with green light, it will appear to be orange. Invisible ultraviolet light (so-called ‘black’ light), for example, is more energetic than any visible colour. It is absorbed and rendered visible by fluorescent materials. They then appear more luminous than normal materials. Fluorescence is not simply a specific colour, it therefore applies to a specific material. Fluorescence is linked to the presence of light. In darkness, a fluorescent material is no longer visible, while a phosphorescent material continues to emit its own light.

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P PHotovoltaic cell

in a single year, the earth receives energy via solar radiation which represents 10,000 times the world energy consumption. each year, every square metre receives an average of 1,700 kwh. in the knowledge that the sun’s estimated life expectation is several billion years, it’s obvious that this is the source of energy we should value the most. the sun’s energy is used today for both heating and cooling. it energises chemical processes which allow, for example, desalination of seawater and is also of course used for electricity production, either by the photovoltaic process or by thermodynamic systems in which the sun’s heat is first converted into mechanical energy and thence into electrical energy. the photovoltaic effect, discovered in 1839 by antoinecésar becquerel, is a physical phenomenon characteristic of semiconductors: when exposed to sunlight, they produce electricity. photons impact the semiconductor surface and some of their energy is transferred to the electrons present in the material. a direct electric current is

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created in each cell and the cells are connected to achieve a desired output voltage per panel of cells or to achieve a desired output current. the efficiency, i.e. the electrical energy produced as a percentage of the solar energy captured, varies as a function of the chosen technology. there are several types of photovoltaic systems, which may even be referred to as different ‘generations’: • the first generation, with several variations, is based on the use of silicon in a crystalline, relatively massive form (silicon wafer). the manufacture of these wafers is energy-intensive, expensive and requires the use of very pure silicon. the conversion energy does not exceed 20%. • other, so-called ‘thin-film’ technologies appear in the second generation, based on silicon again or the tellurides of cadmium, copper, indium, selenium, etc. these open the way to bigger modules and cheaper techniques, facilitating applications. the semi-conducting film is applied directly to a substrate (for example glass). the process is cheaper than in the previous generation

P PHotovoltaic cell (continued)

but the solar cells have a lower performance and some of the elements are toxic (cadmium, for example). some products are based on amorphous silicon, with an even lower efficiency (about 6%) but at a lower cost and allowing flexible products. • the third generation of photovoltaic cells is expected to show a large increase in efficiency. this generation is still under development. current research aims to perfect different types of processes: either transparent cells or flexible, light-weight organic cells which could, for example, be used to make photovoltaic textiles. research is underway on hybrid solar cells based on dyes (one possibility, for example, is blueberry juice) which works in a biomimetic manner, on the way to simulating the phenomenon of photosynthesis. research is focused on increasing efficiency, reduction of production costs and the development of cells which are easy to manufacture. however, although solar energy is considered as renewable, what should not be ig-

nored is that the manufacture of photovoltaic products requires energy and the use, though in small quantities, of toxic elements and that recycling has not been fully mastered yet. photovoltaic cells are used today in various fields, either singly (calculator, garden light) or in groups to form solar panels. they can supply small electronic objects directly or be connected to an energy storage system to provide the energy needed by houses, public installations, satellites, etc.

strong points: long-lasting output, reliability, harmless (noise, movement, smell, emissions), free use of renewable sunlight. Weak points: initial investment, manufacture and recycling are ecologically significant.

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P PIEZOELECTRIC MATERIALS

Piezoelectric materials have the ability to convert mech­ anical energy into electrical energy when they are deformed, and vice-versa. Mechanical deformation, caused by slight pressure, generates an internal electric field. The first piezoelectric effects were noted in quartz crystals, but numerous other materials in the ferroelectric family also exhibit these properties. Piezoelectric materials are in common use today in so-called intelligent devices. These are very often monocrystals of silicon, germanium or doped ceramics. These materials have an ionic structure that is not centro-symmetric. When the centres of gravity of the positive and negative charges in the material are displaced by mech­anical action, the displacement causes the formation of dipoles responsible for the appearance of the electric field. This phenomenon reverses to transform an electric field into a physical change in dimensions. Piezoelectric materials are used as sensors or actuators in intelligent systems in satellites, in active vibration

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monitoring systems (in buildings for monitoring beams, bridge piles); in gas lighters, cigarette lighters or nowind watches; in sonar; in medical ultrasound scanners and in various sensors in cars (suspension, rain, etc.)

Strong points: anti-breakdown devices in cars, no additional energy needed, small dimensions of devices. Weak points: price.

P PLASTER

Plaster is an ancient material, normally made from powdered gypsum (a sedimentary rock) and water. Various additives are used (for example, setting retarder, etc.) to complete the basic mixture. Gypsum is crushed, baked and then ground to form a fine white powder. This powder has the special quality of hard­ening in the presence of water: it sets irreversibly. If setting proves to be too rapid, the resulting plaster can take a very long time to dry completely (up to several days, as a function of the mass). The quality of plasterwork will depend very much on the fineness of the powder, but also on knowhow in the mixing and application of the plaster. Each professional supplier offers variants: plaster of Paris, modelling plaster, plaster to be sprayed, shovelled, etc. It is possible to add colour­ing to plaster, to create stone imitations, for instance. Stucco – lime and plaster – often with a marble powder filler, is an ancient, cost-saving substitute for solid marble.

Staff, a form of plaster with glycerine, sisal, and jute cloth allows ornamental plasterwork (much prized in the 19th century) to be created by moulding. In building, plaster is used as a coating material or in the form of sheets – plasterboard – ready for use (non load-bearing partitions), with water-repellent treatments and coatings with a high resistance to scratches and impacts. Finally, there is polyester plaster. This is a high-strength material, between resin, plaster and porcelain, for smooth and detailed depiction, prized in sculpture among other fields.

Strong points: ease of use, cost, good fire resistance. Weak points: sensitive to moisture, average mechanical strength, slow drying process.

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P PLYWOOD

Plywood is a composite sandwich material, made from wood and adhesive, which allows certain drawbacks and the dimensional limitations of wood to be resolved. It is fabricated from unrolled sheets of veneer, each called a ply, always in an odd number (from 3 to 15 plies) where the direction of the grain is alternated for each ply. At each addition of another ply, a compensating ply must be added in order to maintain the odd number of layers and avoid deformation. The number, thickness and tree species are variable. Standard plywood is often Okoume. There are more technical plywoods, Finnish birch for example. It is necessary to distinguish between ‘beech plywood’, where all plies are beech and ‘beech veneer plywood’, where only the two outer plies are beech. Common thicknesses: every millimetre between 1mm and 10mm, then 10, 12, 15, 18, 19, 22mm and from 25mm, every 5mm up to a maximum of 50mm. Density: between 500 and 700kg / m3

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Plywoods are used in building, furniture, vehicle body­ work, flooring, etc. Some have one smooth, slippery side and a rough anti-skid side for use on stairs, for example. Others can have outer veneers from fine tree species.

Strong points: great dimensional stability, good flatness, homo­ geneous edge on special plywoods (which can be left uncov­ ered), flexibility, equal strength lengthways and perpendicular to this, can be given a fire rating, can be approved for exterior use (vertical), withstands screwing and nailing well. Weak points: average resistance to flexing.

P PLYWOOD, MOULDED

One of the most spectacular forms of plywood is mould­ ed plywood. The moulding never starts with standard flat plywood, but is carried out simultaneously with the gluing of the plies, in a mould. There are many stand­ ard types from different companies – half cylinders, quarter-round, chair seats – for re-cutting according to requirements. Using a standard one is much cheaper than creating a custom mould. There are two different methods of moulding: using a mould and a countermould (in industry, metal heating moulds are used; in cottage industry, moulds can be wooden) or veneers can be pressed, in a vacuum, against the mould inside a heat-welded plastic bag. In the furniture industry among others, moulded plywood gives manufacturers the freedom to create a wide range of two-dimensional shapes. With certain manufacturers now even capable of offering the most astonishing three-dimensional shapes. The veneer sheets are ‘lacerated’ in the direction of the grain and pasted onto

a canvas before being assembled and moulded. Thus divided, they prove to be even more deformable. In the field of ‘flexible wood’, there are also particular tree species veneers, or solid wood with special heat treatments, which lend themselves readily to deformation. Bendyply® (3-ply plywood) or Bendywood® (flexible solid) are examples.

Strong points: elegance and great diversity of form, good mech­ anical strength, good dimensional stability. Weak points: cost, manufacturing difficulty (need for a mould), management of edges.

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P POLYAMIDE (PA)

Maximum temperature for continuous use: 80-120°C. Glass transition temperature (softening temperature): 50°C. Melting point: 220-260°C. Polyamides are technical thermoplastics, which can be semi-crystalline or amorphous. There are various slightly different ones, such as polyamide 6.6, better known under its trade name of Nylon® or polyamide 12, called Rilsan®. Each one has its own qualities. Polyamides are, in the molten state, very fluid, therefore difficult to extrude. In spite of this, various items are made from it. The majority of polyamide parts are made by injection moulding: parts for domestic electrical equipment, cars (cams, gears, carburettor floats), electrical equipment (plugs / sockets, switches, etc.), soles for sports shoes, ski boot shells, flexible links between lorries and trailers, and bike derailleur parts.

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Tanks are made from PA 6 by means of rotational mould­ing. PA 12, among others is deposited as a protective, anti-corrosion covering on metal parts such as dish­washer baskets. Polyamides are also widely used in the form of textile fibres. In spun form, they are found in brushes and garments such as tights. Polyamides are easily fixed by adhesive, fuse well and can even be used for clip-together products.

Strong points: good tensile strength and fatigue resistance - better with 50% glass fibre. Low coefficient of friction (PAs are used for parts subject to friction, mechanical parts, gears, etc.). Good chemical resistance, self-extinguishing, good electrical insulation. Weak points: poor resistance to water, complex to process.

P POLYCARBONATE (PC)

Maximum temperature for continuous use: 125°C. Glass transition temperature (softening temperature): 140-150°C. Melting point: 230-250°C. Polycarbonate is an amorphous thermoplastic material, very resistant to impact. Its transparency is similar (slightly inferior) to PMMA but it has better mech­anical properties. Polycarbonate is extruded to obtain all types of profiles: sheets, honeycomb sheets for building, bullet-proofing protection (sheets, profiles, tubes, etc.). Hollow bodies such as bottles can be obtained by injection blow moulding. Polycarbonate is very suitable for thermoforming, at about 190°C, for fabrication of domes, portholes, windows, car windscreens, etc. At high pressures, it injects well and allows hatches, dials, parts for domestic electrical equipment, optical

parts, protective devices (helmets) and medical equipment to be made. Polycarbonate is easily fixed by adhesive, fuses well (using ultrasound, vibration or friction) and can even be used for clip-together products.

Strong points: resists relatively high temperatures and is rigid up to 100-110°C, allowing it to be sterilised, for example. Transparent, shiny, good electrical insulator, self-extinguishing, author­ised for food industry use, impact resistant. If treated, has good resistance to UV and can be used in architecture. Its chemical resistance is good, but should be tested or monitored in certain cases. Weak points: an expensive plastic, very viscous, complicated in application. Poor resistance to hydrocarbons and washing liquids.

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P POLYESTER (UP)

Unsaturated polyesters (note: saturated polyesters are thermoplastic) are amorphous, thermosetting resins. Often available in liquid form, solidification is triggered by a catalyst. Setting accelerators allow the poly­ merisation time to be controlled to a certain degree. However, polyesters are often sold ‘pre-accelerated’ and manipulating and measuring the amount of accel­ erator can prove to be a delicate procedure. Polyesters can be combined with fillers or fibres which improve their mechanical and electrical properties or fire resistance. They are found in filament windings, for example. They are the most widespread resins in the manufacture of so-called composites (resin plus glass or carbon fibre). Their relatively short setting times favour their industrial use for economically attractive solutions. They are often craft processed (contact moulding or simultaneous spraying of fibre and resin). It is possible to use polyester for injection moulding, with two

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methods: Reaction Injection Moulding (RIM) and Resin Transfer Moulding (RTM). Pre-impregnated materials have appeared recently, making industrial applications easier. These are prepared mixtures of catalysed resin, with either cut fibre (Bulk Moulding Compound, BMC) or fabric (Sheet Moulding Compound, SMC), pressed while hot to make vehicle coachwork parts, for example. Unsaturated polyesters have numerous applications, such as varnish, mastic, reconstituted stone, coachwork, baths, swimming pools, and tanks, boat hulls, etc.

Strong points: medium cost, good mechanical strength. Weak points: tricky in application (toxicity, among other things).

P POLYETHER ETHERKETONE (PEEK)

Maximum temperature for continuous use: 200-250°C. Glass transition temperature (softening temperature): 143°C. Melting point: 334°C Polyether etherketones are a family of polymers with a very technical nature. Semi-crystalline thermoplastics, they are opaque, have excellent mechanical properties: resistance to wear, bending, impact and friction, very good chemical resistance, and above all remark­able heat resistance of up to 250°C and are barely inflammable in normal use conditions. When reinforced with glass fibre, their heat resistance can go up to 300°C. Their properties makes them real competitors to thermosetting polymers. They can be injected and extruded, however, processing them remains difficult. For example, very high temperatures are required for injection. PEEK is often used for coat­ing metal parts, a material it is fully compatible with. PEEK

fibre is used in woven form or filament winding. There are also cloths made from glass and carbon fibre which are impreg­nated with PEEK and used to make longfibre composites. PEEK applications include technical parts in road vehicles, aeronautics and the chemical industry.­

Strong points: mechanical strength, resistance to heat degra­ dation. Weak points: price, poor resistance to UV.

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P POLYETHYLENE (PE)

Maximum temperature for continuous use: 65°C. Glass transition temperature (softening temperature): very wide ranges, they start to soften between 35 and 50°C. Melting point: 120-135°C. A member of the polyolefin family, polyethylenes are semi-crystalline thermoplastics. Low-density and highdensity distinctions are made, the former (often referred to as LDPE) being flexible and translucent and the latter (HDPE) more rigid but with a higher performance. They have a waxy appearance – when burning their smoke smells like burn­ing candle. Greasy to the touch, they mark easily, have a tendency to self-heal, are used in the food industry, are not expensive and very widely used in packaging. They are extruded to produce film with many uses: protection in agriculture and the food industry (transparent when very thin), waste-bin liners, supermarket bags, gas pipes, petrol tanks, and milk bottles.

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Used as a coating material, they provide waterproofing. With rotational moulding, containers and other differ­ent, complex shapes can be made: tanks, reflective road studs, etc. Application of these materials by injection moulding is easy: bowls, paint containers, toys, etc. However these are of limited aesthetic quality. Polyethylene foam is also often used in car heat insulation, protective sports devices, and packaging. Polyethylene can be welded and also used to make clip-together products. However, use with adhesives and the application of paint are difficult.

Strong points: cost, easy in application, good chemical resistance, low coefficient of friction, excellent electrical insulation, use with food, flexible, good impact resistance down to -100°C. Weak points: very sensitive to sunlight, large shrinkage in mould­ ing, moderate mechanical strength.

P POLYETHYLENE TEREPHTHALATE (PET)

Maximum temperature for continuous use: 70°C. Glass transition temperature (softening temperature): 73°C. Melting point: 255°C. PET is part of the saturated or thermoplastic polyesters family, not to be confused with the better-known thermosetting polyesters. PET can be used in extrusion to produce films which can be stretched – which improves their strength – to make packaging, photo or cinema film, film for back-projectors, insulating films, and film for industrial tracing material. Drawn PET filaments or fibres can be used to make ma­ terials known as Tergal® or Dacron®. Filaments can also be used to make ‘non-woven’ or interwoven cloth (filaments welded to each other), used for insulation or ground stabilisation. It is used by injection moulding to make electrical equip­ ment, contactor boxes, connectors, switches, toaster

bases, and mechanical items (casings, bodywork parts). Other things made using injection moulding are bottle blanks (test-tube type) which are reheated and blown to give strong gas bottles (or blown containers). This is now certainly the most important use of PET. Use with adhesives is difficult, but PET can be welded by ultrasound or heating.

Strong points: quite transparent, shiny, good chemical and electrical properties, good mechanical strength, low coefficient of friction, good insulator. Weak points: poor chemical resistance above 60°C, low resis­ tance to fluids used in road vehicles, difficult to use in manufacturing.

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P POLYMETHYL METHACRYLATE (PMMA)

Maximum temperature for continuous use: 70-90°C. Glass transition temperature (softening temperature): 110-130°C. Melting point: 210-240°C. PMMA is an amorphous thermoplastic, often called acrylic or Plexiglas® . A ‘good-looking’ plastic, it is used in decoration, light fittings and furniture. It is un­usual in that it can be applied by casting to cover objects, making it one of the embedding or ‘potting’ resins. It is also easy to extrude and can be used to make sheet, tubing, piping or vehicle trim. Its optical properties (high transparency – for a 3mm thickness, 92% of light is transmitted), mean it is used for optical fibre. Extruded acrylic sheets can be well thermoformed, on the condition that they are pre-heated in an oven. Domes, portholes, windows, and display units are made in this way.

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PMMA works well for injection moulding, for the manufacture of car rear lights, reflectors, and light fittings. Frequently used to make parts by machining, it can be drilled, milled, turned, bent,and polished. Good for use with solvent-based adhesives (pre-heat­ ing to 80°C) or with heat-polymerising adhesives (acrylic and UV), it can also be welded easily, either thermally or with high frequency or with ultrasound.

Strong points: exceptionally transparent (superior to glass), good resistance to UV, shiny, easy to thermoform. Weak points: fragile, breakable, sensitive to scratching (but easy to re-polish), limited heat resistance, sensitive to moisture (has to be heated before transformation), average chemical resistance, combustible (but burns slowly).

P POLYOXYMETHYLENE (POM)

Maximum temperature for continuous use: 90°C. Melting point: 170-180°C. This is a crystalline thermoplastic, a member of the polyacetal resin family, used in engineering, owing to its excellent mechanical properties, good impact resistance and good resistance to heat. Very resistant to friction and abrasion and high fatigue resistance (good hinge and spring effects, very reliable when used in clip-together assemblies). Often compared with polyamides, it has a better physical / chemical performance. Low water absorption and excellent resistance to hydro­ carbons and solvents. Not suitable for use with food. It can be extruded and injected. Often used in mechan­ ical engineering as a substitute for metal parts. Present in cars, domestic electrical machines, ski bind­ ings, aerosol mechanisms, bodies of throwaway cartons, some gears and electronic keyboards, etc.

Difficult to use with adhesives, it can be welded, either thermally or by using ultrasound, but not via a high frequency method.

Strong points: excellent mechanical properties, resistant to impacts, hard, resists heat, high resistance to friction, abrasion and fatigue, excellent resistance to hydrocarbons and solvents. Weak points: not for use with food, difficult to use with adhesives, poor resistance to UV.

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P POLYPROPYLENE (PP)

Maximum temperature for continuous use: 80°C. Melting point: 165-170°C. Polypropylene is a semi-crystalline thermoplastic in the polyolefin family. It is available opaque or translucent and in numerous bright colours. Polypropylene is close to polyethylene, but has better performance in all fields. When extruded, polypropylene can be used to produce protective film, cover sheets (‘tarpaulins’), tubes and pipes for water and gas, as well as filaments which, when woven, can become rope or string. Hollow bod­ ies are also extruded to produce tanks, domestic and industrial containers. Rotary moulding is used to produce polypropylene containers and toys. In addition, polypropylene works well by injection moulding and is used to make items such as small gears and car bumpers.

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It is characterised, among other things, by its high strength and fatigue resistance. Well-designed polypropylene hinges – in packaging – for various items, for example aerosol pumps and stationery, can last for several thousand cycles. PP comes are in the form of non-woven fabrics, such as Tyvek®. Welding of polypropylene is easy and the material can be used for clip-together items, but painting and use with adhesives remain difficult.

Strong points: cost, very easy to use, good chemical resistance, low coefficient of friction, excellent electrical insulation, use with food, high fatigue resistance (hinges, repeated bending), good impact resistance down to 0°C.

Weak points: very sensitive to UV, high shrinkage when moulded, average mechanical strength (better than PE).

P POLYSTYRENE (PS)

Maximum temperature for continuous use: 60-85°C. Glass transition temperature (softening temperature): 90°C. Melting point: 180°C. Polystyrene is a very widespread, amorphous thermoplastic, a throwaway plastic par excellence. It is found in different forms: crystal (general purpose), high-impact (or HIPS, with an additive) and expanded polystyrenes. Crystal polystyrene is shiny but breaks easily; highimpact polystyrene (containing butadiene) is always opaque, more flexible and has better impact resistance than crystal; finally, expanded polystyrene, foamed using pentane gas, is lighter and a sound and heat insulator. Crystal or high-impact polystyrene are used to make injected CD cases, containers, toys and bottom-ofthe-range kitchen equipment. Expanded polystyrene is used for various forms of pack­aging (for example egg boxes), protective wrapping or insulation.

Polystyrene sheets can be extruded to then be thermoformed. Expanded polystyrene sheets can also be extruded to then be used for insulation and packaging. Thermoforming is easy, below 100°C, where the poly­ styrene is very deformable. Yoghurt pots and other food tubs and beakers, as well as kitchen electrical equipment casings can be made in this way. Welding is easy, but with clip-together items, repeat­ed un-clipping is to be avoided. Polystyrene is very easy to use with solvent adhesives, epoxy or cyano-acrylate, etc.

Strong points: low cost, transparent and good appearance of the crystal form (smooth, shiny surface), easy to use with adhesives or to weld, easy to mark, decorate, print on, easy to colour (bright colours), expanded form can be made fireproof. Weak points: sensitive to impact and scratching, very sensitive to chemical agents.

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P POLYTETRAFLUORETHYLENE (PTFE)

Maximum temperature for continuous use: 250°C. Melting point: 327°C. Very well known under the Teflon® trademark of Dupont de Nemours, PTFE is a strongly crystalline thermoplastic, part of the fluoropolymer family. It has exceptional properties of heat resistance and near-perfect ‘antistick’ properties. Its weather and light resistance is total, and its resistance to solvents are the highest of any organic polymer. PTFE is non-inflammable and will not burn under normal conditions. It does, however, have a major disadvantage: when heated, it takes the form of a very viscous liquid and cannot be used with the same equipment and the same procedures as other thermoplastics (notably injection moulding). Available in the form of a white powder, it is moulded under pressure and then heated, in exactly the same way as the sinter­ing technique for metallic powders. It is then cooled in a very controlled manner.

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As the design of solid parts is difficult, it is essentially used in the form of a thin layer or as a coating. Surfaces to be coated must be prepared by being scored, striated, abraded. There is often use of intermediaries to assist adhesion. PTFE can also be sprayed on textiles (for example, conveyor belts). It is widely used in industry, in applications exposed to heat (chemistry, food processing – bakeries, for example); in casseroles, frying pans and cake moulds or on the underside of clothes irons.

Strong points: exceptional heat resistance, anti-stick. Weak points: difficult to apply, cost.

P POLYURETHANE (PU)

Polyurethanes have the special feature of being available either as thermoplastic, i.e. softening with heat, or as thermosetting, i.e. hardening with heat. However, they are most often encountered as the thermosetting type. They are often used with an expansion product to produce honeycomb materials: flexible foams – with open cells, from 10 to 60 kg /m3 – for mattresses and cushions; rigid foams – with closed cells – for thermal insulation in buildings and refrigerators and for pack­ aging. There are also semi-rigid foams, some with an integrated skin, used to make arm-rests, vehicle steer­ ing wheels, and golf-club grips. Polyurethanes are also used for abrasion-resistant varnishes which also have very good chemical resistance. Polyurethane adhesives are useful adhesives which can offer a degree of flexibility in the glued joint. Polyurethanes are often found in the form of elastomers, with good mechanical properties, good resistance to abrasion, to tearing, good tensile strength, good resis-

tance through time and continuous use at a temperature up to 100-120°C. Finally, polyurethanes are more and more available in the form of gels. Originating from the field of medicine, these are very comfortable in use and are found today in the fields of sport and furniture. Polyurethanes are good for use with adhesives and are easily welded.

Strong points: excellent tensile strength, resistance to tearing and abrasion, good chemical resistance to oils including hydrocarbons, good resistance to cold. Weak points: limited resistance to UV.

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P POLYVINYL CHLORIDE (PVC)

Maximum temperature for continuous use: 60°C. Glass transition temperature (softening temperature): 70-100°C. Melting point: 140-170°C. PVC is one of the best known plastics, so much so that it is easy to assume that everything can be made with it. It is an amorphous thermoplastic material, which can be transparent (always a little bluish); dominant in common objects until the 1970s, its place is being taken more and more (for ecological reasons) by polypropylene (PP), poly­ethylene terephthalate (PET) and polyethylene (PE). Calendaring allows a continuous sheet of PVC to be obtained for damp-proof membrane (used under ground concrete), substitution for tarpaulins and oilcloth, imitation leather luggage items and inflatable items. Rigid PVC can be extruded to make pipes, building profiles, sheets, tape, etc. When flexible, it can become garden hose, seat upholstery, and electric cable sheath.

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With injection moulding, PVC can be used to make items such as valves, connectors, and cosmetic containers. Thermoforming is also used a lot to make packaging material. Used for coatings, in the form of a viscous paste called Plastisols, it is used on textiles and metal parts. Use with adhesives and fusing are easy, but decoration is difficult.

Strong points: cost, flexible or rigid, good chemical resistance, good electrical insulation, self-extinguishing and therefore still useful in buildings, easily recycled. Weak points: sensitive to UV, special tools necessary (stainless steel or with anti-corrosion treatment), limited chemical resis­ tance when transparent, poor impact resistance at low temper­ ature (breakable at -10°C), toxic emission of hydrochloric acid vapour if there is a fire.

P PRECIOUS STONES

Precious stones, which encourage dreams of princes and princesses in all of us, are different types of beautiful gems, rather rare and often very hard minerals (hardness of more than 6 on the Mohs scale, in which the maximum is 10). Historically however, the term ‘precious stones’ actually applies only to four gemstones: diamond, emerald, ruby and sapphire, which are each described separately in this book. Following this historical classification there are also semi-precious stones – or fine stones – which are transparent and also highly prized: aquamarine, topaz, amethyst, garnet and tourmaline, among others. The term ‘semi-precious’ is deprecated in the USA and banned in France. The more common ones may also be called fantasy or ornamental stones, for example amber, jade, agate, onyx, obsidian, opal or pearls. These gems are often of mineral origin: crystals discovered in rocks or on the surface in some countries, in alluvial deposits or in the ocean. However, pearls and amber have a biological origin, which explains their

formation. It’s also possible to synthesise certain gemstones artificially or imitate them with coloured glass. All of the so-called ‘precious’ stones are now assessed according to a series of precise criteria: their weight (in carats, where 1 carat is equivalent to 0.2 g), their colour, their purity (also described as ‘clarity’) and the way they are cut. Fashion as well as their provenance also influences their value. The precious stone market operates according to these different aspects and each piece is unique. Their main use is in jewellery, even if some of the stones have very industrial uses. The economic issues involved with precious stones can’t be overlooked and inevitably cause tensions: coveted deposits, exploited miners/ prospectors, etc.

Strong points: beauty, sparkle, hardness, rarity. Weak points: high costs, conditions for exploitation.

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R rare eartHs

contrary to what their title implies, so-called ‘rare earths’ are in fact metallic elements whose abundance on the earth is comparable to that of a lot of the normal metals. this atypical group from Mendeleyev’s periodic table contains 17 elements: scandium, yttrium and the 15 elements in the lanthanide series. their unique optical, chemical, structural, mechanical and magnetic properties have made them essential for various hightechnology applications: they are used in miniaturisation of powerful magnets for telephony, in hard discs, in asynchronous motors, in medical radiography, in flat display screens, batteries for electric vehicles, glass colouring, in oil cracking processes, in catalytic vessels, in fluorescent sources, in night vision devices, in wind turbine generators, in superconducting devices, etc. this apparent but deceptive ‘rarity’ comes from the fact that these elements are generally very dispersed in low concentrations in other minerals (most often in monazite and bastnaesite). they are therefore difficult, and not very

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profitable, to exploit. they are also very randomly distributed in the earth’s crust. china is estimated to have more than 50% of the existing deposits, supplies about 95% of world demand and is also the major consumer. this quasi-monopoly situation inevitably causes some tensions as well as political and economic concerns. the whole rareearth exploitation process, wasteful of energy and polluting, is very questionable. one route followed to counteract these environmental questions, but also to anticipate exhaustion of valuable resources, is to use recycling facilities for the difficult process of extracting small quantities of rare earths that have already been used. however this is a solution which in itself also poses real questions in relation to pollution and working conditions.

strong points: elements which are now essential for high technology applications. Weak points: exploitation difficulty, pollution, strategic issues.

R RUBBER - LATEX

Rubber is a natural polymer. It originates from the secretion of an Amazonian tree: the hevea, which the Indians, who originally exploited it, called the ‘tree that weeps’: cao (wood) and tchu (which weeps), hence the French name: caoutchouc. This soft, sticky gum had a fast rise to prominence after the discovery in 1839 by Charles Goodyear. He succeeded in stabilising it with the aid of sulphur to obtain an elastic material that was deformable and impermeable. Besides many applications exploiting its flexibility and sealing ability, rubber has become an essential element of car tyres, now its major use. Rubber is an elastomer, i.e. it can change its shape and dimensions. It extends up to between twice and ten times its initial length without breaking and regains it after being stretched. Natural rubber (NR), called latex, is in the form of a whitish liquid. It is thermosetting and to become solid it must be polymerised with the aid of sulphur and an accelerator: the process of vulcanisation. Numerous

additives can be combined, such as carbon black in tyres (increased resistance to tearing and abrasion), talc, chalk, anti-oxidants, etc. Rubber can now be chemically synthesised. Even if synthetic formulations have superior performance in a particular field, natural rubber remains the best compromise and the most multipurpose. This explains its numerous applications (in cars, the medical field, balloons, etc.).

Strong points: elasticity, resistance to breaking, good chemical barrier. Weak points: difficult to use in manufacture, difficult to recycle (thermosetting), deterioration over time.

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R ruBy & saPPHire

sapphire and ruby are a variety of corundum. they are evaluated according to their colour, purity (transparency), size and cut. • ruby: chromium oxide is the compound responsible for the characteristic red colour. ruby is very rare and has a hardness of 9 on the Mohs scale (in which the maximum is 10, for diamond among others). it is also resistant to friction and thus wear. today the majority of rubies come from deposits in Myanmar (formerly burma), but they are also mined in Kenya, sri lanka, thailand and cambodia. synthetic rubies have been developed, made from aluminium oxide and red dye. these have no imperfections. the main fields of application of ruby are in jewellery (where they are often cut in an oval shape), tiny ones in clocks and watches (as a bearing material) and in ruby lasers. • sapphire: the best known colour is blue, but there are also sapphires that are colourless, pink, yellow, purple, green, etc. only ruby is red. sapphires consist of alu-

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minium oxide crystals in conjunction with other oxides which cause a particular colour, titanium and iron for blue, chromium for pink, etc. the world’s main deposits are in australia, thailand, Myanmar (formerly burma), Kashmir and Montana. sapphire, natural or synthetic, is mainly used in jewellery but synthetic sapphire in particular also has applications such as optical components in scientific instruments or in the electronics field, where it is used as a thin insulating substrate for semiconductor circuits. it can also be used for watch glasses or portable telephones screens owing to its high resistance to scratching. it can be used to make the envelopes for xenon lights, bullet-proof windows and, in association with composites, protection vests for military use.

strong points: colour, sparkle, hardness, transparency, resistance to friction and thus wear. Point faible : rarity, cost (except for synthetic ruby and sapphire).

S SANDSTONE

Sandstone is a sedimentary rock comprising of sand grains agglomerated together by a natural silica, clay or calcareous cement. This is a consistently homogeneous stone, difficult to saw but which is commonly found in construction in the form of stone paving or cobblestones, for example. Sandstones are also use in sculpture and to make abrasive tools such as grinding wheels. There are different types, distinguished from each other by their colour: from bluish to beige, passing through ochres, reds and even violets. The most sought after are sands­tones with fine grain and close-knit texture.Quartzite (quartz sand­stone, very compact) and molasse (calcareous sand­stone) are among the most common. Sandstones are hard rocks, which have the special feature of continuing to harden after their extraction. They are more or less porous, depending on the exact mode of transformation. Certain geological strata of porous sandstone can also function as water, gas or even petroleum reservoirs. The term ‘sandstone’ is also

used to describe vitrified fired earth ceramics (at about 1,300°C). With the term ceramic sandstone or ‘stoneware’ used for very hard impermeable materials used for floor coverings, for example; enamelled sandstone when the ceramic receives layers of surface porcelain and enamel in the fabrication of sanitary ware; drawn sandstone (instead of being moulded); vitrified sandstone, fine and extremely hard for industrial gutters or slabs, etc. Some items of crockery are also fabricated in ‘ceramic sandstone’.

Strong points: hard rock, homogeneous, strong, durable. Weak points: porosity (for some), more or less fine grain.

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S SCHIST

Schists are metamorphic rocks. The accumulation of sediments (clays, muds) at the bottom of the oceans was subjected to high temperatures and pressures and governed schists formation. Schists have a laminated appearance, often smooth and shiny. The Greek etymology of the word ‘schist’ is significant (from the word ‘to split’); they have a lamellar texture and split along planes of cleavage. They are composed of either clay – argillaceous schists – or mica and quartz, in which case, they are known as mica-schists. There are also bituminous schists, rich in hydrocarbons, from which schist oil is extracted. Slate is a well-known member of the schist family. It occurs in thin layers, producing slabs (in the geological sense) and is often used for roofing, floor covering and was once used as school ‘slates’ to be written on. Recently, slate has appeared more and more in interior architecture, for kitchen work surfaces and bathrooms, in its characteristic colours: from black through to blu-

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ish grey (the most common) to red or violet. Slate can contain quartz, clay, mica, feldspar, pyrite, chlorite or haematite, as well as fossils. It is generally available in thicknesses from 3 to 9 mm, above these – between 20 and 40 mm – the term slab is used (in the everyday sense), or flagstone. Slate can also be used for sculpture and engraving.

Strong points: aesthetic. Weak points: splits easily (slate), price.

S semiconDuctors

these crystalline materials are electrical insulators at absolute zero temperature, but capable of electrical conduction at ambient temperature. they are found in components such as diodes, transistors, photovoltaic cells, integrated circuits, lasers, etc. the observed properties of semiconductors are explained by the theory of energy bands. in a solid, the electrons can take certain energy values. the energy of an electron determines which energy band it inhabits. there are permitted energy bands and forbidden zones. in the case of a metal, electrons circulate throughout the material, moving directly from the last filled, so-called ‘valence’ band, leaving a ‘hole’ there, to go into the next so-called ‘conduction’ band if these two bands are close together. in an insulator, a very wide forbidden zone, called a ‘gap’, exists between these two bands, making it impossible for electrons to conduct an electric current. in a semiconductor, this gap is reduced and, with a little encouragement (in the form of electromag-

netic energy of some kind, including heat or light), electrons go back into the conduction band to move around in the material, producing an electric current. there are intrinsic semiconductors (the conductivity of the material increases with heat) and extrinsic semiconductors for which studies have shown that the regularity of a crystalline structure induces the formation of forbidden bands. germanium and diamond, as well as composite semiconductors such as silicon carbide, gallium arsenide, zinc oxide, copper chloride, titanium dioxide are in the category of inorganic semiconductors. today, there are also lighter, flexible organic semiconductors used in the manufacture of oleds (organic leds) for some solar panels and electronic paper for example.

strong points: very sensitive control of conductivity, miniaturisation. Weak points: recycling, strategic issues.

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S SHAPE MEMORY ALLOYS (SMA)

Shape memory alloys, discovered in the 1950s, have a remarkable property: they are capable of changing shape and then reverting back to their original shape, according to the temperature. Long reserved for military applications, SMAs – some of them biocompatible – started off in medical applications (vascular stents) and are now found in aeronautics or safety equipment (micro-mechanics in hostile environments), for example. SMAs change not by the action of atomic diffusion in a solid body – which would modify the chemical structure of the material – but by a shearing effect involving whole groups of atoms. Atoms do not change place, there is no fundamental change in atomic composition. It is displacement transformation, which enables the memory effect. Their properties therefore depend on their micro structure and the thermo-mechanical treatments – delicate and costly – they are subjected to. The shape memory effect is present in numerous alloys: copper-zinc, nickel

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-titanium and is starting to be explored in polymers and certain ceramics. The forces which appear in polymers are mostly weaker than in metals; in ceramics, weaker as well but faster acting. Depending on the materials used, shape memory can lead to applications that are almost inverse: with shape memory metal alloys, for instance, mostly contact and possible conduction is caused where as with shape memory polymers or shape memory ceramics, one usually aims at precise action to isolate or break contact.

Strong points: miniaturisation potential, reliability, biocompat­ ibility. Weak points: price, limited to small devices.

S SHARKSKIN OR SHAGREEN

Fish skins have been used in cabinet making, luxury case-making (smelling-salts flasks, snuff boxes, dagger sheaths and sword scabbards) and garments, for a long time. Shagreen is the skin of a shark, dogfish or ray. The French name is galuchat, from the name of master scabbard maker Galuchat – in the service of king Louis XV – who introduced shagreen to the West. Shagreen is a rare and precious exotic leather, much exploited in Asia. Its characteristic grainy appearance – seen above all on the dorsal side of fishes – reveals an ‘ivory’ effect when pumiced. With the flesh shaved off, washed, cured, cleaned by sanding on the outer side and scraping on the inner side, the skins are subjected to various preparatory stages before being flattened out and possibly pumiced and coloured, depending on the desired aesthetic effects and planned use. Pumiced shagreen is very fashionable in green. When not pumiced, the skins are very abrasive.

In the Art Deco period, furniture with a shagreen covering was very popular, but this popularity quickly waned after fashion became less ornamental. It is beginning to come back into fashion today for small luxury leather goods, jewellery and some furniture. Other fish, salmon or perch for example, are also exploited for their leather. Paradoxically, the leathers from aquatic animals are not all impermeable. Some are now tanned and treated to make them washable. These are also prized for use in luxury accessories, garments and shoes. Because the size of the skins depends on the size of the fish, only small dimensions can be obtained.

Strong points: aesthetic. Weak points: price (shagreen), small pieces.

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S SHELL

Shell is a precious material long exploited by man, like ivory. Obtained from the carapace of certain species of turtle (the hawksbill turtle in particular), working with it is an art and remains ancestral know-how, still practised in a few workshops in the world. A natural and lightweight material, based on keratin (like hair), its colours vary from dark brown to honey blonde, up to transparency, with astonishing shimmers and patterns. It has incredible plasticity and is easy to work (milling, turn­ing, sculpturing, fusing). Shell is used in sheet form – inlays or veneers – or in solid form. It has a strange capacity to self-amalgamate: just pile sheets of shell and add hot water to create a monolith to work on. This capacity for self-amalgamation allows invisible repairs to be made. Shell has had (and still has) many applications: de luxe marquetry on furniture, spectacle frames (non-slip), elements of leatherwork, decorative boxes, cigarette holders, hair slides, etc.

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In time, shell develops a dull layer. It can be maintained using fine oils. A precious material, available in limited quantities, today’s supplies are regulated. As a result there are a rising number of shell imitations, with plastic materials including cellulose acetate creating relatively good substitutes.

Strong points: weight, non-allergenic, anti-static, easily worked, self-amalgamating. Weak points: price, regulated supply.

S SILICON (Si)

Density: 2,329 kg / m3. Melting point: 1,410°C. Silicon is a chemical element with a decisive role in technology. Present in sand, in the form of silica (sil­icon dioxide), it is an essential component in the manufacture of glass, concretes, ceramics and silicones. In this form, it is an effective abrasive and a cutting tool (highpressure sand jet). Silicon – a semiconductor – is also at the heart of the digital revolution. Abundant all over the world, neither a good insulator nor a good conductor, nothing predisposes it, a priori, for such success. Its behaviour is completely the inverse of that of metals: the higher the temperature rises, the better its conductivity and, a mediocre conductor in its pure state, its performance improves when chemical impurities are introduced – socalled ‘doping’ – such as boron and phosphorus. The resulting electronic components, switches and ampli-

fiers, have allowed continuous improvements in transistors over the last 50 years. Associated with capacitors, they allow the production of solid-state mem­ory: one of the greatest successes for the quantum mechanics theory and a demonstration of its practical application. Today, starting with wafers of very pure silicon (30-cm in diameter) and proceeding through numerous complex operations, millions of transistors are made, capable of controlling billions of electrical ‘contacts’ in integrated circuits. A powerful factor in miniaturisation, silicon seems to have reached the limit of its progress. Prominent solutions now involve new forms of silicon doping, with gallium or arsenic for example, or even finding a substitute for silicon by processing data with the aid of molecules of organic DNA.

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S SILICONE (SI)

Silicones are a very large family of elastomers which are distinguished by the way they are processed or the type of cross linking (some achieved with the assistance of heat) in their structure. Contrary to the majority of other polymers originating from carbon chemistry, silicones are based on silicon. In the form of oil, liquid, paste, gum or resins, silicones serve in shock-absorber fluids, heating fluids, varnishes, polishes, seals, flexible membranes, mould-release agents, and paints. They stick very well to themselves. They allow the fabrication of flexible moulds (sock moulds) into which, polyester and epoxy resins can be poured. However, when using them it is necessary to check compatibility between materials, to avoid mould release problems. It is also very easy, with certain silicones, to take the imprint of fragile objects, and mould copies of old things such as statues, without the risk of damaging them (sil­ icones do not heat up and do not stick). For this work, silicones offer high definition precision.

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Safe to use with food and resistant to high temperatures, the material is ideal for applications in cooking: cake moulds and baking sheets etc. are available today in silicone. Silicones are however subject to ageing and getting dirty. Milky transparency (which yellows quickly) can be obtained, but it will never be possible to get a fully transparent silicone. Hardness of silicones is measured by the Shore (Durometer) test or Rockwell hardness test.

Strong points: excellent heat resistance (-50 to 250°C), antiadherence quality (mould-release), good electrical insulation, biocompatibility. Weak points: price, average lifetime, mediocre resistance to oil and solvents.

S SILVER (Ag)

Density: 10,500 kg / m3. Melting point: 960°C. Silver is a precious metal, grey with a white lustre, ductile and very malleable. It is sensitive to corrosion and quickly forms a dark surface layer. It has bactericidal properties and is recyclable. It is often alloyed with copper (as a small proportion) to increase its mechanical properties, or with gold. It is also used in small quantities in alloys, for example, to increase the mechanical characteristics of aluminium. Used by jewellery makers and silversmiths, for objects such as tableware – silverware – it is present as solid silver or, as plating, a few microns in thickness. Some coins and medals are also made in silver. Its applications in traditional photography or radiography, in the form of photosensitive silver salts, used to be a cause of large consumption, now losing ground with the advent of digital techniques.

Silver is an excellent conductor of electricity, the best in the field, it is used in electrical and electronics applications (conductors, switches, contacts, conductive jointing compounds and inks). It is also found in braz­ing solders and welding rods for jewellery, cars and aircraft. Some surface treatments require silver cyanide. Silver is also present in some batteries and mirrors.

Strong points: precious, malleable, quite ductile, excellent electrical conductor. Weak points: price, corrosion.

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S SOLID SURFACES

‘Solid surfaces’ are synthetic materials. Created by Dupont de Nemours forty or so years ago, Corian® remains the best despite numerous competitors. Made from a mixtures of PMMA resin (acrylic) and a type of aluminium oxide (alumina) as a filler, these materials have excellent characteristics: they are hard; resistant to scratching and impact; resistant to heat; to dirt marks; to UV; to certain acids; they are non-porous (anti-mould) and non-toxic; easy to use, maintain and repair; flame resistant. Among other methods, it is possible to thermoform them (to fabricate sinks, for example) or to prepare moulded parts. Most of the time however, they are used as standard panels; working with solid surfaces comes close to that of a cabinetmaker working with wood. Adhesion with invisible joints, cutting, carving, and en­graving, are all possible with conventional tools. They are found today in solid form or as veneers, not only in commercial and residential interior architecture

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(counters, furniture, wall coverings, light fittings, etc.) but also in the medical sector (work surfaces in surgical units). In general, these materials are available in numerous colours and finishes (plain, speckled, granite or marble effect, etc.). When thin, the material is translucent.

Strong points: hardness, resistance, impermeable, aesthetic, easy to use. Weak points: price.

S STAINLESS STEEL

Stainless steels are a family of alloys based on iron. Their most remarkable property is high resistance to corrosion. It is the addition of chromium (about 12%) which makes steel non-oxidizing. These steels form a layer – or film – of protective passivation on their surface. This layer has the ability to reform in the event of impact or scratching. One could almost call the material ‘self-healing’. Nickel, vanadium and molybdenum also come into the composition of non-oxidizing steels. For example, the addition of 2 to 4% of molybdenum considerably increases the resistance of stainless steel to marine atmospheres. There is therefore not ‘a’ stainless steel but a range of grades refined as a function of the requirements and circumstances. Stainless steels can be brazed and welded reasonably well, but these operations require special precautions compared to ordinary steels. In effect, stainless steels are particularly sensitive to deformation after being heated by welding.

The majority of stainless steels are non-magnetic. The diversity of their applications, means they are found everywhere. Buildings, naval construction, med­ icine, tools, kitchen utensils and food processing are a few examples.

Strong points: resistant to corrosion, food compatible, good mechanical strength. Weak points: rather expensive, rather heavy.

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S STEELS

Density: about 7,850 kg / m3. Melting point: about 1,500°C. Steels are metal alloys based on iron and carbon. The carbon content (which does not exceed 2%) determines their properties, in the same way that the addition (one then speaks of alloyed steels) of other components such as nickel, molybdenum, etc. can modify their prop­erties, allowing special and/or non-oxidizing steels to be obtained. In effect, distinguishes can be made between ‘classic’ carbon steels (the majority, at competitive prices), heat-treated steels (which have been subjected to tempering, annealing or stress-relieving), tool steels and stainless steels (see Stainless steel p.237). Mild steels, medium-carbon steels, high-carbon steels or extra-hard steels are categories depending on their composition. The presence of carbon has a tendency to increase their hardness and their mechan­ical strength while weakening their structure. Beyond 2% of

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carbon, steel becomes cast iron (see Cast iron p.134). Steels are recyclable and a lot will be used in the ‘scrap iron’ channel of the steel production cycle (see Metal p.40). If they are not alloyed and non-oxidizing, their resis­tance to corrosion is mediocre. They can however undergo treatments such as galvanization (surface layer of zinc), lacquering or burnishing to increase their longevity. Steels are widely used in rail transport, cars, building (with specific standards), tools, mechanical devices and furniture.

Strong points: price, recyclable, mechanical strength, mallea­ bility, elasticity, impact resistance, hardness. Weak points: weight, corrosion.

S suPerconDuctors

the superconducting properties of certain materials (often metals) are very promising and of strategic importance. in effect, at extremely low temperatures, close to absolute zero, namely -273.15°c, these materials exhibit zero resistance to the passage of an electric current. among other things, this opens the way to transporting electrical energy without loss. with the ever-increasing need to save energy, it’s obvious that these materials are of great interest. superconducting materials also exhibit a phenomenon of ejection of the magnetic fields that they are exposed to, rendering them capable of levitating magnets. this is the Meissner effect. considerable current research is under way to find materials which exhibit superconductivity at higher temperatures than the level already achieved, approximately 130 K, i.e. -143°c. liquid helium or nitrogen are currently used to cool the materials. superconductivity can only be explained by quantum mechanics and each material, or alloy, has its own precise temperature

called its critical temperature. For example, mercury becomes a superconductor at 4.2 K (-268.95°c), lead at 7 K (-266.15°c). at this point a phase transition is said to occur in the material. the superconductivity of certain materials such as cuprates, which are a combination of various elements with oxygen to form an oxide, for example the ceramic material barium lanthanum copper oxide, is not yet understood. they are called ‘unconventional’ superconductors. superconductors are already in use, in superconducting electromagnets in medical imaging, in particle accelerators like the lhc (large hadron collider) at cern and in some magnetic levitation (Maglev) train systems.

strong points: zero electrical resistance, levitation potential. Weak points: at present, superconductivity temperatures are extremely low.

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T THERMOPLASTIC ELASTOMERS (TPE)

Long ago, elastomer polymers included only thermosetting silicones or rubbers. Although they became indispensable in industrial production operations, they were difficult in application (long polymerisation process, vulcanisation or reticulation, i.e. chemical cross-linking). Chemists turned their interest toward polymers which have chemical associations of both rigid and flexible phases. These hybrid materials are now known as thermoplastic elastomers, or TPEs. The flexible phases are often dominant in their construction and provide an elasticity that is almost the equivalent to conventional elastomers. The only usage limits still problematic today are their resistance to high temper­ atures. In effect, the best TPEs are not operational above 100°C. The appearance of TPEs nevertheless constitutes a nificant advance in production using elastomers sig­ (ration­ alisation and shorter production time) in the sense that their application is simplified and it be-

240

comes possible to inject or extrude them using conventional tools. To some extent, TPEs can be considered as recy­clable. They are found in road vehicles, shoe soles, and thermofusible adhesives. There are four large families of thermoplastic elastomers: based on styrene; based on olefins, such as pol­ ypropylene in rigid phase and rubber in flexible phase; based on polyurethanes and based on polyesters.

Strong points: elasticity, easy to use, cost of production, recycling. Weak points: residual deformation, poor resistance to high temperatures (>80°C).

T TIN (Sn)

Density: 7,310 kg / m3. Melting point: 232°C. Tin is a silvery-grey, soft malleable metal, moderately ductile at ambient temperature. In nature, it is found essentially in oxide form. It can be easily laminated in thin sheets and does not change with exposure to air. Resistant to corrosion (sea water and soft water), it does not really resist strong acids. Apart from dishes and traditional decorative objects, tin – added by electrolysis, immersion or chemical deposition methods – is used as protection for steel sheet. It is then called tinplate, commonly used for canning. It can also protect copper. These are tinning oper­ations, which also provide good electrical contact. It is found in the field of soldering: brazing with tin or tin-copper or silver-copper alloys, is important in the electrical and electronics fields. Tin also comes into the manufacture

of float (completely flat) glass, where the glass spreads over the surface of a bath of molten tin. Finally, it is used in alloy form with niobium, as the constituent of a superconducting material (at a temper­ature of 19K, namely -254°C) or, more simply, alloyed with copper to produce bronze. It is also involved in antifriction alloys. Certain organic derivatives of tin can prove to be toxic to man.

Strong points: malleability, corrosion resistance. Weak points: toxicity in certain forms, soft at ambient temperature, mediocre resistance to acids.

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T TITANIUM (Ti)

Density: 4,508 kg / m3. Melting point: 1,670°C. Titanium is a metal which was discovered in the 18th century, but was not used until 1950. Although abundant on earth, its transformation to a metal product is expensive. The strength / weight ratio of titanium is exceptional. It has a higher strength than steel but weighs 40% less. Its resistance to corrosion is also high. Titanium can be passivated and its auto-protection is better than that of stainless steel. It can be alloyed, with aluminium, molybdenum, vanadium, to increase its resistance to corrosion or make it biocompatible (for the manufacture of prostheses, for example). Titanium is non-magnetic and its electrical conductivity is similar to that of stainless steel. It is used today in numerous highly-specialised applications: spectacles, medicine, aeronautics, and extremesports equipment. It also appears in the form of pig-

242

ments (90% of titanium is used to make pigments or white paint) for paint or plastics, improving their weather resistance and lifetime, due to its capacity to absorb UV.

Strong points: strength / weight ratio, corrosion resistance, biocompatible. Weak points: price.

V VENEER

First made using rare and precious woods, there are now three techniques for cutting veneer from solid wood: • By hand sawing: The oldest technique. This gives the most beautiful veneers, which keep their colour. Their thickness is from one to several millimetres. This limited production is now reserved for veneer used in the renovation of antique furniture. • By cutting with a blade: The wood, steamed prior to cutting, is fixed and cut with a large moving cutting blade. The cut veneers range from tenths of a millimetre up to 6 or 7 tenths of a millimetre. These are often fine species, intended for cabinet making. Depending on the orientation of the length of tree trunk with respect to the machine, more or less pronounced veining and patterning are obtained. Cut veneers are often made up in bundles to be matched up (reconstitution of the decorative patterns) and are limited in dimensions to the diameter of the tree).

By rotary cutting: Steamed lengths of tree trunk are mounted in a lathe and cut by a fixed blade while the trunk is rotated, like a pencil sharpener. The long, continuous sheet of veneer is then guillotined. The thick­ ness varies from several tenths to a few millimetres. Of lesser quality, this type of veneer is the most common and the most industrialised; it is used to make various plywoods and packagings. The dimensional advantage is evident, but there are less decorative effects. Today, so-called ‘reconstituted’ veneers are produced, by lathe cutting or sawing pieces of ‘re-assembled’ wood. Numerous decorative effects are possible.

•

Strong points: thin, aesthetic quality. Weak points: fragile, price (for some).

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W WOOD POLYMERS

Wood polymers (sometimes called ‘liquid wood’) are a family of materials between wood and polymers, composites obtained essentially from recyclable wood products (shavings, sawdust or dust/fibre). Semi-finished products comprise in general mixtures of 55 to 70% of wood, with the addition of thermoplastic polymer resins (30%) which are often high-density polyethylenes. Wood polymers can be used in the normal way, like thermoplastics: injection and extrusion are possible, and the same traditional ways of working solid wood (sawing, drilling, nailing, screwing, etc.) are easy. These composite materials are to be found in many applications: decking, footbridges, steps, landing stages, swimming pool edges, outdoor furniture. Some composite materials using various fibres (hemp, flax) coupled with polymer resins are described by the term ‘wood polymers’. There are many formulas for the vegetable base of the mixtures formed.

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Strong points: rotproof, fungus resistant, dimensional stability, made from waste wood, recyclable, touch and appearance close to solid wood, no protection finishes necessary. Weak points: mechanical strength less than solid wood, aesthet­ ically a bit too much like plastic material.

W WOOD, RETIFIED

Retified wood is obtained by a special treatment, similar to roasting the wood throughout. Many tree species are suitable for retification but as the technique is relatively recent, mainly beech, ash, poplar, spruce, maritime pine and Scots pine are used. The principle consists of raising the temperature of the wood, in a very precise manner, in a reactor (200-260°C) in a controlled atmosphere (absence of air). After retification, wood can be considered as a new material, as it has become rot-proof and hydrophobic, without its mechanical properties being notably affected. The classic shrinkage of wood is reduced by 50%, it seems less susceptible to insect attack and much more durable over time. Ret­ ified wood can be worked in the same way and with the same tools as non-retified wood. It can be glued, planed, varnished, painted, etc. Depending on the extent of its treatment and the species of the wood to start with, it becomes brown to very brown in colour, which remains homogeneous. Retified wood gives off no

odour. Retification – with performance comparable, or better than other wood treatments – allows wood used for external applications to be treated without the use of polluting chemicals (as is the case up to now with copper ions for example). The increasingly reasonable cost of this material makes it ideal for applications in exterior architecture (cladding panels, street furniture, flooring, terracing, garden equipment etc.).

Strong points: non-polluting treatment, weather resistance with­ out additional finishes. Weak points: price, no light coloured wood.

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W

2

6

WOOD SPECIES 3

1

4

5

1 FIR (Resinous) Relative density 0.40 to 0.60 Wood creamy-white, little odour. Appearance close to spruce, but less durable. Used in joinery and structural woodwork. 2 SPRUCE (Resinous) Relative density 0.40 to 0.55 Wood yellowish-white. Sapwood not distinct. Usage very close to fir, but its grain is straighter, allowing its use in fine woodworking. Christmas trees are generally young spruce trees. 3 RED IRONWOOD (Broad-leaved) Relative density 0.95 to 1.10 (i.e. does not float) Very hard and heavy wood, very dark in colour, almost chocolate. This is a wood with very high mechanical strength and its main applications are: structural timbers and parquet flooring.

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4 OAK (Broad-leaved) Relative density 0.60 to 0.80 Wood light yellow to dark brown. Characteristic sap­ wood to be removed. Hard, with coarse grain. Depend­ ing on sawing, very specific decorative radiating lines. Common uses: parquet, structural woodwork, cooper­ age, interior and exterior furniture. 5 CEDAR (Resinous) Relative density 0.40 to 0.50 Wood cream to reddish brown. Straight, fine grain. Sometimes a little brittle. Excellent stability and durability. Very beautiful finish when varnished. Used in fine woodworking and in outdoor furniture. 6 BIRCH (Broad-leaved) Relative density 0.50 to 0.60 Creamy-white, semi-hard, homogeneous and easy to work. Used in turning, crate making, plywood.

W WOOD SPECIES (continued) 9

7

10

8

7 WILD CHERRY or CHERRY (Broad-leaved) Relative density 0.60 to 0.70 Wood light reddish to pink. Fine and homogeneous grain. Sapwood usable. Beautiful when polished. Used in rustic furniture and cabinet making, either in solid form or as veneer. 8 WALNUT (Broad-leaved) Relative density 0.60 to 0.75 Wood grey to brown, veined, glistering, dense, easy to work, fine grain and rather hard. Beautiful when pol­ ished. Widely used for cabinet making – in solid form or as veneer – in turning and by gunsmiths. As veneer, it has notable burrs (then known as burr walnut). 9 POPLAR (Broad-leaved) Relative density 0.40 to 0.50 Wood white to yellowish in colour, soft and homogeneous. Frequent presence of cross-graining. A light

11

wood used for battens and laths, in packaging (e.g. Camembert boxes), match manufacture, paper pulp or whitewood furniture to be painted. 10 LIMEWOOD (Broad-leaved) Relative density 0.45 to 0.50 A white wood which can turn slightly pink. No distinct sapwood. A little waxy to the touch, with rancid odour. Regular and straight grain. Mediocre mechanical strength, soft and quite brittle. Has a tendency to warp and split. Often used in sculpture, turning, modelling, mould fabri­­cation, piano keys, etc. 11 SYCAMORE (Broad-leaved) Relative density 0.55 to 0.75 Wood creamy-white, straight or wavy grain, soft and homogeneous. Popular for use in stringed instruments, turning, veneering, giving a beautiful finish. Never used outdoors.

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W WOOD SPECIES (continued)

12

16 14

13

15

12 CHESTNUT (Broad-leaved) Relative density 0.60 to 0.70 Wood colour cream to brown, coarse texture, very obvious rings and very little sapwood. Used in rustic furniture, structural woodwork and fencing. Interesting fact: spiders avoid it. 13 WENGÉ Relative density 0.80 to 0.95 Dark brown wood, with narrow blackish veining. Grain rather coarse and generally straight. Sapwood whitish and very distinct. A durable wood which resists decay well. Quite high mechanical strength, good impact resistance but splits quite easily. Main applications in veneer, cabinet making, parquet, seats and as decorative wood. 14 LARCH (Resinous) Relative density 0.55 to 0.70 Wood red-orange with a characteristic sapwood that

248

is not extensive . One of the hardest of the resinous woods. Suitable for parquet and exterior use: posts, fences, flooring. 15 MAHOGANY (Broad-leaved) Relative density 0.40 to 0.80 The mahogany family includes great variety with slight differences. These are woods pink to red-brown in colour. These varieties give some of the most beautiful patterns in cabinet making: glistering, flamy, dappled, ribboned, very popular in the 19th century in decorative veneers. Applications of mahogany are: veneers, marquetry, furniture, cabinet making and decorative panels. 16 BEECH (Broad-leaved) Relative density 0.60 to 0.75 Light-white, with characteristic small brown spot mark­ ing. American beech is slightly pink. A hard wood with tight, homogeneous grain, somewhat difficult to work

W

17

WOOD SPECIES (continued) 20

18

with. Used in furniture, workbenches, panelled tables, chairs, turning and plywood. Often used for bentwood (a steaming process developed by Frenchman Michael Thonet in the 19th century). 17 OKOUME (Broad-leaved) Relative density 0.40 to 0.50 Pink wood, salmon, homogeneous, soft at the heart, not difficult to work. However cross-graining often present. It is used in cabinet making, moulding and above all in plywood manufacture, as it produces large diam­eter logs. 18 ASH (Broad-leaved) Relative density 0.70 to 0.80 Coarse-grained white wood with veining. A hard wood, but notable for its flexibility. Often used for bentwood. Applications are: cabinet making, veneers, sports e­quipment (skis), boat building and bentwood for furniture.

19

19 PINE (Resinous) Relative density 0.40 to 0.85 Colour of wood varies from pink to reddish. Sapwood substantial, to be taken out. Very strong resin odour. Used in glued laminates or in the chemical industry (to recover the resin). 20 TEAK Relative density 0.55 to 0.80 A greenish-brown wood which darkens and goes grey in light. As it ages, it acquires coppery glints. Grain quite coarse with relatively heterogeneous structure which can cause problems in working. Characteristically fatty to the touch, specific leathery odour. Essential to re­move sapwood. High resistance to decay and high dimen­ sional stability make teak good for exterior use. Medium mechanical strength. Difficult gluing and varnishing, so oiled or waxed finishes preferred. Its applications in­ clude: boat building, exterior furniture, parquet.

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W WOOD SPECIES (continued)

23

25

22

24

21 VIOLET WOOD (Jacaranda) (Broad-leaved) Relative density 0.80 to 0.95 Wood with purplish ribbon patterns. White sapwood to be discarded. Comes from a tree with very tight grain. Available pieces are necessarily small, therefore expen­ sive. Very good mechanical properties. Veneers, marquetry, inlays, small deluxe objects. Threatened species. 22 IROKO (Broad-leaved) Relative density 0.60 to 0.75 Yellow to brown. Very easy to work with. Good resistance to moisture. Main applications are for outdoor woodwork. 23 ROSEWOOD (Broad-leaved) Relative density 0.80 to 1.15 (i.e. does not float) Wood light to dark brown to violet. A heavy and durable wood, with relatively coarse grain. Its applications are: deluxe cabinet making - in solid form and as veneer and in stringed instruments. Threatened species.

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21

24 EBONY (Broad-leaved) Relative density 1.05 to 1.25 (i.e. does not float) Depending on its origin, black wood. Macassar ebony has regular yellow and black veining. Very characteristic white sapwood to be discarded. Heavy and dense, with very tight grain. Trees are quite small diameter. Often used in veneers or for making small objects. Applications in marquetry, cabinet-making, inlays, stringed instruments, fancy goods. Threatened species. 25 BALSA Relative density 0.10 to 0.23 Light wood, almost white in colour. Extremely light weight, soft and brittle. Quite coarse fibres. Little resistance to scratching, but when it is cut perpendicular to the grain, it has a strength/weight ratio which is one of the best performing materials in composite form. Widely used in modelling, as the core of sandwich panels, as a sound and thermal insulator, and as floats.

X XX-CHROMATIC

There are different types of materials which are capable of changing colour as a function of their environment. • Thermochromic materials: These change colour as a function of temperature. There are reversible effects and irreversible effects. There are some liquid crystals (mesomorphic bodies between the amorphous state and the crystalline state) and encapsulated leuco dyes which are pigments capable of such changes. Liquid crystals are more precise but the temperature ranges over which they change colour are quite restricted, as the colour change is due to a modification of the reflection of light wavelengths on their structure. Heat-sensitive inks using leuco dyes – colour pigments which, when heated, lose their colour and regain it once cooled – are active over a wider range of temperatures between -25°C and +66°C. They can be combined with pigments or standard dyes. Numerous applications: temperature indicators such as thermometers or ‘intelligent’ labels, markings to prevent counterfeiting, ‘best-before’ indicators, etc.

Photochromic materials: These change colour as a function of exposure to ultraviolet light. Used for example for spectacle glass, toys and gadgets. • Hydrochromic materials: These change colour in contact with water or moisture. • Electrochromic materials: These change colour with the passage of an electric current. This changing colour can be due to heating or triggering of the thermochromic properties of a material or may be the result of rapid oxido-reduction causing a change in colour. Once the colour change has been obtained, the new colour persists until a new reverse electric charge allows a return to the initial colour. For example, electrochromic windows are available. •

Strong points: changing effects. Weak points: limited and restrictive temperature ranges for thermochromic materials, price, stability and lifespan.

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Z ZAMAK ALLOYS

Density: 6,600 to 6,700 kg / m3. Melting point: 380 to 400°C. ZAMAK is an old trademark for a family of alloys of zinc with aluminium (about 4%), with very small quantities of magnesium and copper. The name is an acronym from German: Z for Zink (zinc), A for Aluminium, MA for Magnesium and K for Kupfer (copper). It is also known sometimes as ZAMAC. Aluminium makes zinc pour more easily, which allows the alloy to be poured into a mould under pressure (an economical procedure which resembles injection). The advantages of these zinc alloys are: low melting point (380 to 400°C), they flow easily to give high precision for complex diecast parts – particularly those with very thin walls – and reduced production costs. In fact they come close to plastic materials. They accept var­ ious finishing techniques, electrolytic, chroming, patinas and bronzing. They have excellent corrosion resistance,

252

they are also resistant to petrol, motor oils, alcohols and even sea water. The applications of ZAMAK include: automobile industry (carburators, petrol pumps), plumbing fittings, cheap ironmongery parts, domestic electrical appliances, small containers, and fantasy jewellery.

Strong points: cheap, light, resistant to corrosion. Weak points: low mechanical strength, average heat resistance.

Z ZINC (Zn)

Density: 7,135 kg / m3. Melting point: 420°C. Zinc is a bluish-white metal, with mediocre mechanical properties, obtained from ores such as zinc blende (the common name for sphalerite – zinc sulphide) or smithsonite (zinc carbonate). For a long time, it was considered as a variety of tin. The main use for zinc (almost half of its production) is a result of the fact that it is highly electro-negative with respect to steel: it serves essentially to protect steel against corrosion, i.e. it is a ‘sacrificial’ metal. Deposition of zinc on steel can be performed either by hot-dip galvanising (immersion in liquid zinc) or by electrolysis. Galvanised steel is characterised by its high resistance to atmospheric corrosion (it forms a white coating of impermeable zinc oxide, known as ‘flowers of zinc’ on its surface), it is often used in building, in large or small sheets for covering, cladding or guttering. A lot of zinc is also used as an

alloying element with other metals (brass, ZAMAK, and sometimes bronze, for example). It is malleable and can be rolled between 100 and 200°C. Above that, it becomes brittle. Around 50°C, it will be ready for stamping or pressing. Zinc has astonishing healing properties in medicine and can be found in various therapeutic creams.

Strong points: very high corrosion resistance, cheap solution for metal treatment. Weak points: mediocre mechanical properties.

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03 PROCESSES

CUTTING p.260  / FOLDING, BENDING p.264  / MACHINING p.268  / ASSEMBLY p.272  / BONDING p.278  / HEAT SEALING p.284 / SEWING p.288 / STAMPING p.290 / FOUNDING p.292 / FORGING p.294 / SINTERING p.296 / CAST MOULDING p.298 / RESIN MOULDING p.300 / CALENDERING p.302 / INJECTION p.304 / EXTRUSION p.308 / ROTATIONAL MOULDING p.312 / THERMOFORMING p.314 / DIGITAL PROCESSES p.316 / PRINTING p.320 / FINISHES p.324 / RECYCLING p.330.

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Make the right choices

Machining

Thermoforming

Welding

Rotational moulding

Numerically-controlled process

Folding

Resin-injection moulding

Cast moulding

Injection

Printing

Sintering

Forging

Founding

Finishing

Extrusion

Stamping

Cutting

Sewing

Calendering

Use of adhesives

Mechanical assemblies

The aim of the three tables below is to facilitate the choice of fabrication process by looking at three important parameters: what material is being used, what quantity of parts is to be produced and what sort of geometry do they have? Obviously, in reality, there are many parameters to be taken into account (aesthetic, geographical, political, etc.) and they go beyond these three aspects of fabrication; however, it gives a guide to the complex, constantly developing, multitude of fabrication process possibilities.

Ceramic Composite Concrete Glass Leather and skin Metal Paper and cardboard Plastic Stone Textile Wood

Choice of fabrication procedure as a function of the material used

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Thermoforming

Rotational moulding

Numericallycontrolled process

Folding

Resin-injection moulding

Cast moulding

Injection

Sintering

Forging

Founding

Extrusion

Stamping

Calendering Single part

Small cottageindustry run ( 450°C) terms such as soft soldering, hard soldering or braze welding distinguish the process. Easy to implement, cheap, few deformations of the pieces to be soldered; almost all metals and alloys can be soldered. The mechanical strength of the solder, however, remains low. This procedure can be used to join metals of different natures and is widely used in plumbing, jewellery, and the production of small items.

cal procedure is generally reserved for hand and on site welding: ship building, steel works, car production. This procedure involves large dispersions of heat throughout the pieces to be welded, which can cause immediate or gradual deformations and sometimes even breakages.

GAS METAL ARC WELDING Gas metal arc welding (MIG: Metal Inert Gas, TIG: Tung­ sten Inert Gas and MAG: Metal Active Gas) are evolutions of arc welding where the electrode is replaced by an inert gas (e.g. Argon). This type of welding is becom­ing very quick thanks to the automatic feed of a variable diameter filler wire. High precision and strong thick­nesses are possible, and it is highly automatable. However, substantial investment is required.

OXY-ACETYLENE WELDING Oxy-acetylene welding is a weld where the energy required comes from the combustion of oxygen and acetylene. It can be used for soldering, braze welding, and autogenous welds.

ARC WELDING Arc welding consists of an electrical arc between an electrode (the filler rod) and the pieces to be welded, which creates a rise in temperature (2,400 to 3,200°C) and local fusion of the metal (of the rod and the pieces), giving a long-lasting join. This fast and economi-

RESISTANCE WELDING The work pieces are placed together. A low voltage, high intensity current is then passed through them, causing very localised fusion which creates the weld. The two types of weld most often used are spot weld­ ing and seam welding. Welds without additional metal are easily automated (e.g. the manufacture of welded tubes).They limit the possibility of distortion but need efficient clamping systems and careful cleaning of the faying surfaces to be welded. These are the most wide­ly used welds for fine metals sheets, car manufacture, and mechanics.

285

FRICTION WELDING The work pieces are joined by the heat generated from friction. One of the work pieces is rotated and repeat­ edly heated by friction causing fusion. The abrupt interruption of the rotation and a constant pressure guarantee the weld. This is a clean procedure, which is easy to implement, cheap, and can be used to assemble pieces with different profiles.

LASER WELDING A laser beam initiates localised fusion of matter. This high-end procedure could well become automated. It can weld in awkward places, and causes very few deformations. It is possible to machine the pieces before welding. Galvanised steel, gold, zinc, and silver are difficult to laser weld.

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electrode

ELECTRIC SPOT-WELDING

electricity generator

LASER WELDING

drive roller

CONTINUOUS ELECTRIC PIPE-WELDING

knot stitch

1

running stitch 2

3

single-thread overlock

4

5

6

7

zigzag stitch

8

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10

STITCHES (left), LEATHERWORK (right) 1 assembly with cut edge 2 glued-back 3 shaped-edge 4 mixed assembly 5 reversed-edge 6 covered-edge 7 turned-in edge 8 turned with strip or band 9 angle-cut 10 joined

Sewing Leather and skins, paper and cardboard, plastics, textiles, . Sewing is one of the main mechanical assembly methods for flexible materials, particularly textiles and leathers. An ancient procedure, which is done manually, sewing has always been present on a domestic scale, but is now mechanised in most applications. From Grandma’s sewing machine, right through to huge industrial machines, the main principles of sewing remain the same: only the rate of production and the solidity of the join varies. It is said that one ‘sews’ by hand and ‘machines’ when using a sewing machine. Sewn pieces, textile or leather, can take on three dimensional forms due to sewing, sometimes forming shapes that are totally unexpected. Its tendency to distort and twist is exploited to create ‘architectural’ clothing − which can be used to defy gravity; or indestructible structured luggage; and skilful furn­iture coverings.

There are several classic textile sewing stitches: • Running or Straight Stitch: This is the basic stitch, simple and classic, fast but not very strong. Smaller and closer together stitches give a stronger and neater line of sewing. • Basting Stitch: A running stitch where small and large stitches alternate, quite spaced-out, for a fast but rela­ tively weak join. It is often used to prepare seams which are then re-sewn by machine. • Slip Stitch: Two stitches on the front followed by one stitch on the back, this machine stitch is very solid and difficult to unpick. • Back Stitch: A hand sewing stitch which gives very solid sewing. The thread moves in the opposite direction to that of sewing during each stitch. • Zigzag Stitch: A machine stitch used on borders and edges to avoid unravelling. • Overlock Stitch: A stitch used to prevent unravelling at the borders and edges of fabric. Hems are often oversewn in this way.

(threads such as coated polyester thread, silk thread, linen thread, satin thread, and sometimes thread which has been treated to give water-tightness to the seam) will pass much more easily through holes which have been previously made. The sewing is also neater and more regular when prepared in this way. It is sometimes used to reinforce a glued bond (in shoes, for example). There is a real art to assembling leatherwork and leather goods. Some examples are shown in the accompany­ ing diagrams.

Numerous variations are, of course, possible. Aesthet­ ic qualities, but also solidity of the join, and difficulty in unpicking all affect the choice of the right sewing stitch. The threads available for use also have variable char­ acteristics and must be chosen carefully. In leatherwork and the production of leather goods, much of the work is still done manually, especially for luxury items, such as those produced by Hermès, for example. The stitches used are quite similar to those for textiles. A needle − called an awl − is used to pierce the leather before sewing. The thread to be sewn

289

8

1

top-ram

blank

stamping mould

3

METAL STAMPING 1 hydraulic press 2 clamping the blank 3 press closure 4 press opening

blank-holder

2

4

Stamping Paper & cardboard, metal, textiles, leathers & skins. Stamping is a piece-by-piece deformation process, done at cold temperatures, using flat sheets of metal (called blanks) which take a three dimensional shape. This process is widely used in the automobile, domestic appliance, and pack­ aging industries.

METAL STAMPING: HOW IT WORKS Stamping is done by stamping presses, which are very powerful machines. The sheet is held in a blank-holder (to avoid folding) above a fixed matrix. The moveable press tool, comes down with force to push the metal into the shape of the matrix. The hollow matrix has the final form of the piece’s exterior. The press tool has the final form of the piece’s interior (taking the thickness of the sheet into consideration). The process can be done with one or more strokes (in the case of multiple strokes, intermediate size matrices may be used, to gradually bring the matter to its final state). The maximum heights and depths of metal stamping are fixed by the plasticity of the metallic matter. In the case of deep stamping, the metal is also heated to avoid defects associated with cold hammering. The most common stamped shapes are conical or cylindrical, with large angles of curvature (generally greater than 5 times the thickness of the sheet). Stamp­ed metal must respect the rules of draft angles. Today, the fine mastery of stamping procedures and the quality of finishes, mean that stamping can be done directly onto sheets of pre-coated metal. The economical benefit of this is unquestionable.

VARIATIONS Metal may also be stamped by hydro forming, where the press tool is substituted with a fluid under high pressure (or an explosion), which pushes the sheet onto the matrix in a similar way. These complex techniques have the advantage of being able to remove the constraints of draft angles from matrix design as matrices can even be made to open out into several parts.

Advantages: mass-production, this is a fast procedure. Disadvantages: high initial investment for tools, pieces of constant thickness (beyond the phenomena of drawing), and not all metals can be worked in this way.

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2

1

4

5

3

7

6

SAND MOULDING 1 / 2 making imprint of master pattern in sand 3 taking master pattern out of mould 4 positioning inserts 5 pouring metal 6 extraction of part / removal of inserts 7 finishing part (deburring, etc.)

1

4

2

5

3

6

7

LOST-WAX MOULDING 1 machining the mould 2 making the fusible core 3 coating the core with refractory material and baking 4 melting of core 5 pouring the metal 6 destruction of mould to obtain the part 7 finishing the part

Founding Metal. Based on fairly rudimentary principles, founding is a wide-spread industrial procedure which produces moulds and cast pieces made of metal or liquid alloys, like cast iron, aluminium or bronze. This technique can minimise the need for forming and machining. Founding gives greater freedom in the three dimensional design of products. Complex and hollow designs can be achieved, for example cast iron radiators, crankcases for motors, etc. This manufacturing procedure involves specific rules of design: a respect for draft angles (pieces must be able to be lifted out of their moulds), anticipation of phenomena such as dimensional shrinkage, even distribution of mass to avoid defects like cracks (tears) or blowholes (cavities due to the contraction of solid particles during solidification of the metal).

The two main moulds which coexist are: permanent and non-permanent moulds.

NON-PERMANENT MOULDS: HOW THEY WORK The mould is only used once and is destroyed in order to remove the piece. There are two main procedures: • Sand casting: This is a widely used procedure. Around a model, which can be removed, sand is compacted to make a mould, either manually or mechanically, within a frame. The frame has two or more parts and it is these which determine the planes of the joint. The sand used is either green (moist) sand (where clay is used to make it moist), or sand mixed with resin. Once the sand is firmly packed, the two (or more) parts of the frame are opened and the model is removed. The mould is then ready to receive the molten metal, via a pouring channel which has been included for this purpose. This is gravity casting. Once the metal has solidified and cooled, the mould is destroyed to extract the piece. The sand can be recycled to create new moulds. To make hollow features, a sand negative of the desired hollow part is included in the pattern. These may be made separately and added to the mould before cast­ ing, to be destroyed along with the mould. • Lost wax casting: The principle is the same as with sand casting, the only difference being, that the basic model is made of wax and will be lost. The molten metal

takes the place of the wax model by destroying it. This procedure avoids planes of stress at joints and angles since the model and mould are both destroyed during the process. The process also works with expanded polystyrene in place of the wax.

PERMANENT MOULDS: HOW THEY WORK In this case, the mould is reusable, and the process is also known as die casting, done either by gravity or under pressure. This procedure is similar to that of injection. It is suited to multiple production of pieces within each run. The die casting moulds are made of special steel or cast iron. They allow low-cost casting, of aluminium alloys such as zamac, for hardware and decoration.

Advantages: complex forms, large pieces, flexibility of production (unique pieces or large runs). Disadvantages: difficult to obtain thin sections, amendments nec­essary after removal from the mould (de-burring etc.), high initial outlay for permanent moulds.

293

upper die

rough

bur ?

bur blank

pattern

meeting face

lower die

DROP-FORGING

hammer

1

anvil

BLACKSMITH’S FORGE

2

Forging Metal. Forging is a piece-by-piece production procedure which refers to the plastic deformation of a block of metal at high temperatures (between 800 and 1,200°C) or at cold temperatures, by the action of a strong pressure or shock. Forging can be done by hand: this is known as free forging, according to the old techniques of the blacksmith, using a hammer and anvil. It is suited to small production runs, even single pieces as the tools are simple and the implementation can be quick. On an industrial scale, a power hammer is used for a mechanised version of free forging or a hydraulic press for drop forging and stamping. The following can be forged: normal steel, brass, and aluminium alloys, for instance. Within these families certain types have greater or lesser ability to be forged.

DROP FORGING AND STAMPING: HOW IT WORKS Metal, in the form of a workpiece (calibrated block) is heated, and placed between two matrices which have the shape of the final piece. Under high pressure or shock, the matrices close and the matter takes the de­ sired form. The pieces are often treated as preforms which are then machine corrected to obtain the final piece. It is desirable to maintain the simplest and straight­ est joint plane between the two matrices and to avoid drastic changes to the sections or direction. The shape of a drop-forged or stamped piece must allow free flow of the cast matter. The best shapes are round, or gener­ously curved, and obey the rules of draft angles. The procedure retains, and can even reinforce, the fibre direction of the matter. Forged metal has great anisot­ ropy and preferential orientations of grains, the pieces obtained therefore have better mechanical properties. The forging procedure for metallic pieces can be used to make strong tools (keys, spanners, knives) or mechanical pieces which will be subjected to heavy loads during their work lives. It offers a flexible means of production: diversity of shapes and weights (from a few grams to a few tonnes) for forged pieces. Forge machines are characterised by the force they are able to deliver (from 500 to several tens of thousands of tonnes for very powerful hydraulic presses), their velocity of penetration, and stroke frequency.

Advantages: forged pieces have greater mechanical strength compared to machined or moulded pieces, large shape alterations are possible, increased production rates. Disadvantages: large energy requirements, mediocre precision, pieces must be corrected.

295

1

2

3

DIAGRAM SHOWING PRINCIPLE OF SINTERING 1 assembly of grains 2 compaction 3 heating

Sintering Plastics, metals, ceramics. Sintering is a piece-by-piece manufacturing procedure, using compressed powders which are heated to below their melting point. It primarily concerns ceramics and metals. In the case of ceramics, the process involves sintering with a binder, in the case of metals the process does not generally require a binder.

SINTERING WITHOUT A BINDER / POWDER METALLURGY: HOW IT WORKS For metallic sintering, the powder is first highly compressed into a matrix (under considerable pressure) to obtain a preform. This will then be heated in a vacuum or under a con­ trolled atmosphere, to a temperature lower than the melting point of the principle constit­uents of the powder. This heating phase is known as the sintering phase. The grains of matter become joined together. After sintering, the preform will shrink. The preform must therefore be designed to shrink to the dimensions of the desired final piece. Once the compensation factor for this issue is perfect­ ed, the sintered pieces are generally precise, and can be used directly. Sintered pieces are porous, the gaps between the grains are irregular and can constitute up to 30% of the volume of the piece! This defect, can, in some cases, prove invaluable for parts which must be intrinsically porous, like filtration components. By impregnating the pieces with lubricants, the components may also become self-lubricating. Sintering is also a round-about way of perfecting pseudo-alloys. By mixing metal powders together, alloy-type pieces can be created from metals which would otherwise be incompatible by classic fusion (due too diverse melting points for example), the metal with the lowest melting point imprisons the grains of metal with the higher melting point. The procedure of metallic sintering is mostly used for locks, domestic appliances, permanent magnets (iron, nickel and cobalt, titanium and aluminium), brake pads (glass, graphite, iron, and bronze), and light bulb filaments (tungsten).

SINTERING WITH A BINDER: HOW IT WORKS Not all situations allow powders to be compressed. So to obtain a preform which holds its shape in such cases, a binder must be used. In the case of clay and ceramics, water is the most common binder. It creates a paste called slip which helps to make a preform before it is heated. Preforms are either created by hand, moulded, or extruded. The water evaporates from the slip during firing. Some binders disappear during the sintering phase, like water and some polymers: they evaporate or are burnt off. Others remain and partly ensure cohesion in the finished product. This is the case for tools tipped with tungsten carbide where the binder, cobalt, is metallic. It reinforces the solidity of the piece and reduces its porosity.

LASER SINTERING Today, laser ‘sintering’ has become a buzzword. The term can lead to confusion, however, and the technologies it describes are grouped, in this book, under the heading of ‘Digital Processes’ p.316.

Advantages: no need to amend pieces, economic procedure if used on large production runs, controlled density, hard products, isotropic products. Disadvantages: large production runs, fragile pieces, porous pieces, a complex procedure.

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slip

mould

1

2

4

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6

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SLIP CASTING 1 filling the mould 2 mixing or vibrating 3 adhesion of a fine layer of slip (barbotine) 4 emptying the mould 5 draining / drying the product 6 opening the mould

Castmoulding Metal, ceramic, thermosetting plastics, glass, concrete, plaster. Gravity cast moulding is a piece-by-piece moulding procedure using liquid matter. Small ornaments, sculptures, and small bits of hardware are the products of this type of moulding. There are two types: open mould or closed mould.

OPEN MOULD CASTING: HOW IT WORKS

VARIATION: SLIPCASTING

An indentation is made from a piece called the model, master model, or master which produces the inverse of the product’s shape (contreform). The mould pro­ duced will be made of a refractory material when cast­ ing metal or metallic alloys, plaster for casting plaster or resin, steel for casting glass, and thermoset resin reinforced with fibres for casting resin and plaster. A new generation of silicone moulds is now being devel­ oped which bypass the need for back-tapering (draft angles) and release agents. Apart from silicone, all moulds need release agents, which prevent the pieces sticking to the mould. Liquid matter can be cast very easily using just the force of gravity. One side of the piece is exposed to air. In the case of thermoset resin, the use of a catalyst solidifies the piece. For other materials, hardening occurs due to evaporation or cooling.

For casting ceramics in liquid form, as slip, the term slip­ casting is used. The mould, often made of plaster, is filled with slip. Upon contact with the walls, the matter hardens and a crust forms, which is almost solid, but still moist. The surplus is emptied out. Drying causes shrinkage which aids the removal of the piece from the mould. Drying is completed in the open air. Many terracotta pots are made in this way.

CLOSED MOULD CASTING: HOW IT WORKS By the same procedure, casting can be done into moulds made up of two halves (or more parts). Matter is introduced via a casting hole and the air within the mould escapes through vent holes. Generally, the mould is opened before the matter (plaster, for ex­ample) is fully solidified. This finishes off the drying process, or polymerisation for thermoset plastics.

Advantages: very simple procedure, economical, can be done on a non-industrial scale. Disadvantages: very low production rates, filling difficulties, thin pieces impossible, matter is not highly compressed in the mould.

299

brush or roller gel coat resin fibres (mat or cloth)

mould

CONTACT MOULDING (WET METHOD)

Resin moulding Plastics, wood, composites. These procedures are reserved for thermoset resins. These tech­ niques add fibres (often glass fibres, or carbon fibres, for example) to plastic matter (epoxy resin or polyester) to reinforce the structure of shapes. They are known as stratification techniques. Materials made in this way are non-recyclable.

CONTACT MOULDING / ‘WET’ MOULDING: HOW IT WORKS Shapes are created from a negative mould. So work must be done ‘back to front’ as it were; starting with the mould, by applying the final layer, which determines the surface state of the object. This first layer is called the gelcoat. This is then followed by layers of glass fibre, carbon, Kevlar®, etc textile, or non woven fibres, impreg­nated with resin − called mats. Between each layer, care is taken to remove bubbles from the piece to ensure good cohesion. This can be done using rollers or a vac­uum. The resin can be applied quite easily with a brush or spray gun (this is known as simultaneous spraying). Once the resin has polymerised, at cold or hot temperatures in an incubator, the whole thing acquires marvellous mechanical properties. Boat hulls, car bodywork parts, furniture or architectural decoration, bicycle frames, and surf boards are all made in this way.

‘DRY’ COMPRESSION MOULDING: HOW IT WORKS More and more procedures are appearing to industri­ alise these techniques, particularly in the domain of car bodywork and structural elements. Resin/fibre com­ posites are pressed into shape. SMC (Sheet Moulding Compound) or BMC (Bulk Moulding Compound) are often used for this procedure. The procedure involves strong compression, at hot temperatures, between a mould and a counter-mould, of a matrix of fibres which

are roughly oriented and pre-impregnated with resin (also known as pre-preg). The results have very good mechanical properties, and the strength/weight ratio is excellent. However, production rates are still low and the shapes possible are limited (draft angles, no sharp angles).

VACUUM OR BAG MOULDING: HOW IT WORKS This procedure, mostly craft-based, can be used to create layers (thermoset resin and glass fibre or paper reinforcements), giving a quality which is sometimes greater than that of contact moulding. This is also how moulded plywoods are made. It needs little initial investment. A positive mould and the matter to be moulded are introduced into a plastic bag which is hermetically sealed. Depression by vacuum pushes the matter against the mould and removes all the air bubbles (which ensures good homogenisation of the composite). Production rates are low (one piece at a time) but the possible shapes are numerous and more importantly, large prod­ ucts are possible.

Advantages: low initial outlay, great mechanical strength, flexibility of production (from unique pieces to small runs, to make small or large pieces). Disadvantages: the procedure does not lend itself to high productivity, badly-controlled thickness.

301

1

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PLASTIC CALENDERING 1 agitator, mixer 2 z-calendering 3 engraving roller 4 cooling roller 5 winder

Calendering Paper, cardboard, plastics, metal, textiles, leather, skins, glass, ceramics. Calendering, lam­ inating, and drawing all aim to produce, by plastic deformation, plates and sheets, but they can also be used to make some structural shapes. Thermoplastics and paper are calendered, while glass and metals are rolled and drawn. These continuous procedures are either used alone or alongside other techniques such as extrusion. Their principle is no more complicated than that of a rolling pin. Hot or cold, under high pressure, they involve flattening matter between successive cylinders. The main aim of these processes is to end up with a material of constant and precise thickness; often very thin. During the process, rollers can also be used to ‘print’ patterns onto the matter. This is how we get grooved, embossed, and larmé effects. This type of procedure may be applied to all materials which are capable of plasticity and is very widely used: products can be made by the kilometre. At the end of the machine, the matter is either spooled into reels or cut. The lengths, widths, and thicknesses of ready-to-sell products that we find in catalogues are deter­mined during this stage of the manufacturing process. This is also where dimensional standardisation of semi-finished products takes place. Once calendered, rolled, or drawn, the matter will be strongly oriented, in other words it will not have the same mechanical properties in all directions. This may be an advantage or a disadvantage, depending on the final application.

PLASTIC CALENDERING: HOW IT WORKS

GLASS DRAWING: HOW IT WORKS

The plastic is heated and rolled between two or more rollers until it forms a continuous sheet. In terms of production, calendering is viable from 1,000,000-m upwards.

The principle of drawn glass was perfected at the beginning of the 20th century. This is the main mode of industrial production for flat glass. A sheet of glass is continuously and vertically drawn, after being passed through a hole in a refractory piece called a débiteuse, which is submerged in a bath of molten glass. (see drawing 2 p.57) There is also a process of drawing for polymers. Polyethylene is drawn at hot temperatures and fixed to acquire the property of ‘thermo-retractability’. Often used in electrical components (thermo-retractable sheaths) or in packaging, when it is reheated, the product retracts (the molecular structure relaxes and returns to its initial position).

Calendering has a number of variations, according to the materials used and the desired result. This tech­ nique will eventually include the effects gained by diestamping (artificial leather effect, for example), print­ing, coatings of metallic films, etc.

METAL ROLLING: HOW IT WORKS Based on the same principles, metals can undergo processes of rolling at hot or cold temperatures. At cold temperatures, mechanical properties (hardness, for example) will be modified by the subsequent deformation in a phenomenon similar to strain-hardening.

Advantages: high productivity, can be applied to multilayered products, continuous thicknesses. Disadvantages: matter becomes orientated.

303

1

ram

feed hopper

2

3

plastic injection 1 softening 2 injection 3 opening mould / ejection of part

softening ram

heater bands

injection nozzle

mould

Injection Plastics, metal, ceramic. Injection moulding is a fast, piece-by-piece manufacturing procedure which is widely used because it gives high quality moulded objects, often without any finishing process required; even for complicated shapes and extreme dimensional tolerances. Injection is considered the sole territory of plastic matter however, metals and metallic alloys such as zamac (zinc-based) or brass, and ceramics may also be injected at low temperatures. The dimensions of injected plastic pieces can vary from a few millimetres to several metres (some car bodywork and garden furniture are injection moulded). With regards to metal, only the more modest parts are injection moulded (cases for gear boxes, small bits of hardware).

PLASTIC INJECTION MOULDING: HOW IT WORKS Plastic granules are melted by the heat and friction in an injection screw and injected at high pressure (between 500 and 1,500 bars) and temperature into a mould which is then closed by a system of hydraulics or motors. The mould will have a clamping force of several hundred tonnes and include a cooling system which is carefully thought out so that the matter solid­ifies evenly. The piece is removed after the mould is opened. This procedure is used for thermoplastics, sometimes reinforced with short fibres and for some thermoset plastics or elastomers when used with an adapted machine. The design of injection moulds (an important task, often verified by specialised design offices or mouldmakers) depends on the geometry of the piece to be injected. Moulds are usually made of special, highly resistant steels and are precision-machined (and therefore expensive!). Moulds are mostly made in two parts (one fixed, the other mobile) which are hollowed out to give a cavity which is the inverse of the product’s shape. They can also have one or more cores to form hollow areas inside the piece and pins and slides to create openings in the walls of the object. Inserts may also be placed into the mould which will stay in the injected piece, or decoration may be added which will be firmly fixed to the surface (‘in-mould’ procedures). In order to be removed from the mould (which will be reused several times), the shape of injected pieces must not lock the piece into the mould; it must have a draft angle (minimum 2%) to aid the removal of injected pieces.

The position of the joint planes is aesthetically crucial. Always visible, they occur at each junction of the var­ ious parts of the mould. It is therefore best to study their position carefully during the mould design proc­ ess, before the procedure begins. Finally, the channels through which the plastic flows towards the chamber (the runners) will also solidify so their position, and that of any extractors pins or plates, must also be carefully planned so that they leave only minimal traces on the final piece (little ‘bumps’ are left by supply channels and ‘circular marks’ are left by extractor pins). These marks really identify an injected piece. Pieces must be carefully thought out to ensure even thickness of the walls. This will avoid common defects such as shrink marks (shrinkages and deformations caus­ed by uneven cooling). In terms of production, injection moulding remains viable from 100,000 up to 1,000,000 pieces (or more, if the moulds are well looked after.) Nowadays possibilities of injection moulding on a small scale are being developed, mostly to make prototypes. The cycle − production time for one single piece, ending with its removal ready for the next piece − varies from a few seconds to sev­ eral tens of minutes, depending, of course, on the size of the pieces.

Advantages: high work rates, productivity, complex forms, and precision. Disadvantages: large initial investment for the machines and moulds, currently reserved for mass-production.

305

CO-INJECTION MOULDING: HOW IT WORKS

VARIATION: CERAMIC INJECTION

Two different, yet miscible, mattters are injected together to obtain a skin and a body, each having specific prop­erties. This can greatly reduce costs (using a ‘cheaper’ fill for the non-visible core, made of recycled plastic, for example!)

Nowadays, procedures for ceramic injection moulding are being developed. This method can be used to produce crock­ery (for non revolutionary shapes). Simplified injection presses, similar to injection presses for thermoplastics, are used. Ceramic matter is injected as slip at low pressure (approximately 40 bars) and low clamping forces (approximately 75 tonnes).

AIR MOULD / GAS INJECTION MOULDING: HOW IT WORKS Gas is injected along with the matter. This gives hollow pieces. Savings in terms of matter, weight, strength, etc.

MULTI-MATTER INJECTION MOULDING / BI-INJECTION MOULDING: HOW IT WORKS Several matters are injected almost simultaneously, to obtain pieces with different areas, joined together. The demarcation between the various matters appears as a clean line.

INJECTION BLOW-MOULDING: HOW IT WORKS Injection blow-moulding is used to make fizzy drink bottles where the lid must be airtight. A preform or parison which has been created by previous injection, is reheated and placed between the two halves of a new mould. It already has the shape of the cap and this part will be protected so it is not distorted. A rod or pipe is introduced into the preform and air is blown in. Under pressure, the preform swells to fill the walls of the mould cavity which are cooled, thus forming a hollow body. By comparison to extrusion blowmoulding, injection blow-moulding gives better control of the thickness and better air tightness at the lid is achieved. However, the manufacture of the preform is an extra process (injection, storage, then blowing) compared to extrusion blow-moulding (which is a continuous process).

VARIATION: INJECTION MOULDING OF THERMOSET PLASTICS Thermoset plastics can be injection moulded. This is done using either machines in which the necessary ponents for polymerisation are brought together com­ or with low-pressure RIM (Reaction Injection Mould­ing) procedures (mostly used for polyurethanes), or RRIM (Reinforced RIM, where the thermoset plastics are linked to fibre reinforcements).

306

moulded part

sprue

ejector die cavity

movable side of mould

guide post

injection nozzle

thermoplastic polymer

INJECTION MOULD

temperature regulation channels

fixed side of mould

1

3

5

6

2 4 7

Extrusion 1 granules of material 2 endless screw 3 heater band 4 extrusion die 5 cooling device 6 marking 7 cutting

1

2

3

EXTRUSION BLOW-MOULDING 1 extrusion of the parison 2 blow-moulding 3 cooling / opening the mould

Extrusion Plastics, metals, glass and ceramics. Production on a kilometric scale! Extrusion is a continuous manufacturing procedure used, not only to obtain granules of thermoplastics (which will then be injected or re-extruded), but also, and more importantly, to create semi-finished products such as structural sections, piping, panels, and sheets. Extrusion forms the basic production technique for thermoplastics – in fact it is the procedure which transforms the most matter in this domain – but other matter which can also be extruded includes metallic alloys, glass and ceramics (production of hollow bricks, for example).

PLASTIC EXTRUSION: HOW IT WORKS

CO-EXTRUSION: HOW IT WORKS

Thermoplastic granules are poured into the hopper (a sort of funnel) to a heated cylinder. An Archimedes screw then pushes the mass to be extruded forwards, compressing it, plastifying it (softening it) and homogenising it. In front of the cylinder, a die gives the plastified mass its desired cross-sectional shape or profile (to make a pipe, rod, or flat sheet). There are very diverse forms of die. Flat dies give plates, sheets, and films which are often rolled after extrusion. An extruder works a bit like a meat-mincer or a spaghetti machine! As it leaves the machine, the product must be cooled. This is usually achieved by pulling it through a bath of water. For some complex shapes, during the final phases of setting, the product goes into a cooling block which helps the piece hold its shape. Cutting – to standardised lengths – done with a circular saw, completes the extrusion process. Markings (for validity of gas tubing, product mark, various indications, decoration) can also be added to the product during this last stage.

Two or more materials are simultaneously extruded and joined together as they pass through the die. Various colours of one matter; various states of one matter (foamed and compacted, or a layer of recycled material between two layers of compacted, for example); various compatible materials can be obtained this way. This procedure is often used in the extrusion of wires, films, and panels. The co-extrusion of films can play on various layers of materials, giving increased resistance to gas, acids, UV, or water vapour.

Extrusion has a tendency to orientate the molecular chain within the matter; the matter becomes ‘stranded’, it is orientated and constrained. This can be seen as either an advantage or a disadvantage, depending on the use of the product. For example, a plate of extruded PMMA (acrylic glass) will not give the same thermoform­ing or machining results as a cast plate. In terms of production, extrusion is viable for very large quantities; from 100,000-m upwards.

Sheathed electrical wire is made by a special type of extrusion. Effectively, the thermoplastic sheath is extruded directly around the wire, usually made of copper. The wire is pulled whilst the sheathing coats it. Cooled and tested (for insulation and centricity), it is then wound onto reels.

BLOWN FILM EXTRUSION: HOW IT WORKS The plastic matter is extruded through a ring-shaped die to create a tubular sheath which is then quickly inflated and drawn over several metres. The die may be called a ‘bracket head’ through which air is forced into the plastic bubble vertically. Once cooled, the bubble is then flattened into a film and wound onto reels. Instead of winding, it can be cut and heat sealed to make plastic carrier bags, for example. It is mostly PEHD, PEBD, and PP which are extruded like this to make films and bags.

309

EXTRUSION BLOW-MOULDING: HOW IT WORKS After extrusion, the matter (glass or thermoplastics) in rough tubular form (parison) or as a malleable lump is placed into a mould. A blow-pipe is placed in the parison and air is blown in, inflating the matter (which is kept hot) and pushing it into the walls of the mould. Hollow pieces are made using this method, e.g. glass or plastic bottles. Extruded plastic bottles are rec­ognisable by the ‘scar’ left when the matter is pinched as the mould closes. Contours are less precise than those of injection blow-moulded bottles, their aesthet­ics and their thickness tolerance is less controllable. The water-tightness of lids on extrusion blow-moulded bottles is also dubious. This procedure can be applied to multi-layer products, and allows the manufacture of large-volume containers (up to a few hundred litres).

METAL EXTRUSION: HOW IT WORKS Used on metals and alloys (generally of aluminium), metal extrusion is similar to the extrusion process de­ scribed earlier: a press pushes a billet or slug of the matter through a die to make various profile shapes (solid, hollow, or semi-hollow). When extrusion is done at hot temperatures (for aluminium, the temperature nears 500°C), the product undergoes various thermal treatments afterwards to ensure strength and hardness. The product may also be drawn to guarantee straightness and may be subjected to finishing process like cutting, drilling, milling. Cold extrusion is more like rolling (see Calendering p.302).

Advantages of plastic extrusion: economic production technique, continuous productivity, extrusion of many types of thermoplastics (flexible, rigid, expanded). Disadvantages of plastic extrusion: not viable for thermoset plastics, not suited to small-scale production, mediocre dimensional tolerances after direct extrusion, the matter becomes orientated.

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INFLATION EXTRUSION 1 blower 2 angular extruder head 3 blowing a bubble 4 cooling 5 winding / cutting

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ROTATIONAL MOULDING THERMOPLASTICS 1 polymer powder put into mould 2 set in rotation (movement about two-axes) / heating (oven) 3 cooling 4 mould opened, part

extracted

Rotational moulding Plastics. Rotational moulding is a piece-by-piece manufacturing procedure reserved for thermoplastics, which can be used to make a hollow body without welding or bonding. The cost of manufacturing the moulds is relatively low, with the simplicity of implementation making the creation of large pieces possible. Balls, kids’ toys, tanks, road blocks, septic tanks, and port-a-loos are all made this way.

THERMOPLASTIC ROTATIONAL MOULDING: HOW IT WORKS

VARIATION / CENTRIFUGATION THERMOSET PLASTIC: HOW IT WORKS

The matter, in the form of fine powder or liquid, is measured and then poured into a mould − normally steel or aluminium − and generally made up of two parts which are welded together. This mould is then mechanically rotated around two perpendicular axes. The matter spreads out uniformly over the inner surface of the mould under the effect of rotation. The whole thing is then placed in an oven and heated until the matter joins together, once the matter has solidified by cooling, the piece can be removed from the mould.

A similar procedure can be used with thermoset resin (often polyester). Reinforcements in the form of short fibres are placed with the resin into a mould which turns at very high speed. The resin and reinforcements mix closely together under strong centrifugal action, with the polymerisation of the resin accelerated by adding heat. Hollow bodies can be made in this way, e.g. tanks and tubes. This technique competes with filament winding (see Composites p.72).

While all thermoplastics can be rotational-moulded, some are more suitable than others, like polyethylene, rigid or flexible PVC, ABS, polyamides and polyurethanes. Hollow pieces, either open or closed, are made in this way. If necessary, multilayered walls and inserts can be created. Rotational-moulded pieces generally have inferior mechanical properties compared to injected or blow-mould­ed pieces. Thicknesses are difficult to control and accord­ing to the distribution of the matter when rotation begins, weaknesses (or conversely accumulations) of matter may appear. This difference can be compensated for by increasing the thickness, but this can cause greater dimensional shrinkage and general geometrical defects.

Advantages: large pieces, hollow bodies, and strong thicknesses are possible, small production runs are viable, the procedure is economical. Disadvantages: thicknesses of pieces cannot be guaranteed, the inside surface is often poor, slow production.

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blank-holder

blank

mould

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THERMOFORMING OF THERMOPLASTICS 1 heating the blank 2 raising the mould 3 application of vacuum 4 cooling 5 cutting (removal of part)

Thermoforming Plastics, glass. Thermoforming is a piece-by-piece manufacturing process, used for the most part on thermoplastics, to make limited quality products. Many packaging materials are made in this way (yoghurt pots, biscuit trays) as well as fridge interiors, for example. The dimensions of thermoformed pieces can vary from a few centimetres to more than a metre. This simple technique, which consists of transforming a sheet of matter by distorting it against a contreform, involves variations of thickness which can damage the final strength of the object. In addition, as only one side of the object is in contact with the mould, precision − both mechanical and aesthetic − cannot be guaranteed on the other side. This is why thermoforming is reserved for packaging or the manufacture of bottom-of-therange objects. The interest of the procedure lies in the fact that it may be used to create moulds out of wood, composites, or aluminium with low initial investment.

PLASTIC THERMOFORMING: HOW IT WORKS

VARIATION

The sheet of thermoplastic is clamped into a frame (blank holder) then heated until sufficiently soft. It is pushed and deformed over a model by suction and then cooled. After removal, a process of trimming (by sawing or punch cutting for thin films) is necessary to get rid of the edges.

Thermoforming is also used as a technique for shaping glass − but gives less pronounced shapes than in the case of thermoplastics. The variations of form obtained are often two dimensional (curved glass, for example). In this case, the sheet of matter is placed on a refractory model while cold and then heated in an oven or kiln. Once softened, it is able to take on the shape of the mould. The deformation is permanent after cooling.

The shape of thermoformed products is subject to the rules of draft angles. Thermoforming moulds can be convex or concave, according to the side of the piece which requires the best precision and surface state. While, in theory, all thermoplastics should be able to be thermoformed, some are better suited than others. Cast PMMA or polyethylene, for example are not terribly well-suited to thermoforming. By contrast, the following materials are readily thermoformed: high-imp­act poly­ styrene, ABS, extruded PMMA, PET-G, PVC.

Advantages: economical production techniques, adaptable to

In terms of production, thermoforming is viable for 1,000 to 10,000 pieces or more. Generally, it is actually trimming which is the most costly part of the process.

small production runs, low initial investment, complex shapes. Disadvantages: large losses of matter, a constant thickness is not guaranteed.

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STEREOLITHOGRAPHY 1 CAD – CAD-CAM workstation 2 laser beam 3 mirror 4 point-by-point solidification 5 photosensitive polymer resin tank 6 movable plate 7 plate descent

Digital processes All materials. Perfecting digital technologies and developing software capable of controlling tools has lead to the coupling of information technology with machinery. The first machines equipped with digital controls were conventional: metal milling machines, mechanical lathes, routers (wood industry), etc. This pushed for an optimisation of tooling processes and a mastery of the geometry of very complex pieces (curved forms which deploy into space). These first generation techniques, which operated by removing matter, for the most part quickly found their place in industrial production. Now a new generation of processes is making an appearance. Still limited to prototype production rather than mass production, they are characterised by the fact that they work by adding matter. A large number of these processes employ digital technology, laser technology, and the distinctive properties of resin polymers. These technologies are expanding and evolving so fast that we can only describe them in terms of the main principles or the most representative systems. STEREOLITHOGRAPHY

FUSED MATERIAL DEPOSITION (FMD)

Developed in the middle of the 1980s, this procedure is now certainly the most widely used. The machine is made of a laser which projects its beam onto the surface of a tank filled with photosensitive resin (epoxyacrylate). The movement of the beam is controlled by a moveable mirror, piloted by a computer. Following a path defined by a programmed section of the object, upon contact with the resin, the laser beam causes local polymerisation of the resin. Once the section has solidified, it moves down by a thickness (of approximately 0.07-mm) into a tray and the laser begins the whole process again on the next upper section.

This procedure is not very widely used. Thanks to the movement of an articulated arm on three axes, an extruded thread of molten thermoplastic polymer (polyamide, polypropylene, or ABS) − which instantly solidifies − makes the contours of the desired form, section by section.

Constructed layer by layer, this process can be used on complex geometric pieces, three dimensional work, both inside and out of a closed object. This highly spectacular and innovative technique still remains slow, however, and is reserved mostly for prototype production (a few small runs of objects have been made). It is relatively expensive and only used to produce modestly sized polymer objects.

Faster and cheaper than stereolithography, this proce­ dure is less precise and only works with thermoplastics.

LOM LAMINATION (LAMINATED OBJECT MANUFACTURING) The desired form is made a section at a time from a stack of paper sheets covered in polypropylene. Each sheet added is cut with the help of a laser, and then stuck to the others by strong compression and heat. This economical procedure is often used to make master casts for founding. The pieces manufactured by LOM look like bakelised wood pieces. Closed piec­es are not possible.

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Stratoconception® is a variation of this kind of lamination, designed for manufacturing large pieces. Panels, either laser-cut, water-jet cut, or milled, are then joined together by bonding and compression.

LASER SINTERING From polymer powders (which can be loaded with aluminium, bronze), unusual shaped objects can be produced (but never completely closed objects as the residual powder must be removed). Just like the procedures described earlier, each layer is worked sep­arately, with powders added to each new section, agglomerated by the laser where necessary.

3D PRINTING Various procedures are being developed: 3D photo­ copying, where an existing object can be felt and reproduced by production techniques which work layer by layer, alternating between powder and glue. Some machines, called 3D printers, like the ink jet printer on your desk, are capable of depositing pow­dered matter layer by layer (approximately 0.1-mm each) thus creating three dimensional objects in a few hours. These machines will remain expensive for the time being, but the procedure is in the process of being made more widely available. Thanks to this type of printer, in tomorrow’s world, the control of object files created by designers may be done over the Internet, allowing each piece to be made in several copies at home. Faster and more economical (once the invest­ment for the machine is made) than other rapid prototype production technologies, the quality of the pieces is, however, inferior (grainy texture etc.). Colour models are also possible.

Advantages: freedom of form; easily creates a prototype or an object without having to go through a mould manufacture process, for example; personalisation of each piece in a run is possible. Disadvantages: creation time is probably just as lengthy; price, surfaces need to be retouched; limited choice of materials.

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FUSED MATERIAL DEPOSITION (FMD) 1 CAD – CAD-CAM workstation

2 extruded plastic 3 heating nozzle, melted filament 4 layer-by-layer depositione

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Stratoconception ® 1 CAD – CAD-CAM workstation 2 laser cutting beam 3 paper layers + resin 4 movable plate 5 extraction of part

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TYPOGRAPHY (top), SILKSCREEN PRINTING (bottom) 1 screen 2 ink 3 scraper 4 printed material 5 obscured mesh 6 open mesh 7 frame

Printing All materials. Here are just a few of the main printing procedures. The choice of procedure depends on the type of printing substrate, the number of copies required, the quality desired, and the budget. TYPOGRAPHY

PAD PRINTING

Certainly the oldest printing procedure, typography was already being used in China, well before Johannes G. Gutenberg perfected the Western printing press in 1450. The principle revolves around the assembly of independent characters ‘in mirror image’ (made first from wood, then lead, or copper) to create texts or drawings. Typographical characters are arranged into families (roman, serif, etc.), into fonts (Arial, Times, Helvetica, etc.), and into font style and size (bold, italic, size 12, etc.) The size is measured in ‘points’. These same parameters are used in modern word processing interfaces. Similarly, typographical codes, created around the constraints of the old printing procedures, are still used today, for example, the rules of punctuation within this book. Typography is still used for small print runs, in artistic publication, or for business cards, for example. Raised print can also be created.

With the help of a silicone or rubber pad, a coloured pattern can be deposited onto the piece to be decorat­ed. To make a four-coloured pattern, four pads are necessary. Pad printing can also be done on curved shapes and all types of matter. This is the method used to mark CDs, for example.

FLEXOGRAPHIC PRINTING This printing procedure uses elastomer shapes placed on a rotating cylinder − the plate − which, once inked, puts the desired patterns onto the printing substrate. The inks are liquid and contain very volatile solvents. Flexographic printing can be used on paper or cardboard, in the manufacture of sacks or packaging, and also on plastics or metal.

GRAVURE PRINTING OFFSET PRINTING This printing procedure plays on the opposition of water and ink (an oily body). A photosensitive plate is fixed to a rotating cylinder (the relief created by the image is almost non-existent). The ink is fixed but the water is pushed away from the areas to be printed. The ink image, in negative, is transferred onto an intermediary cylinder − the blanket − which then prints onto the printing substrate in positive. Computer-aided offset is one of the main printing procedures for paper. The relationship between quality and cost is highly viable. Magazines, books, telephone directories, and posters are all printed this way but it can also be used to print polymers and metals. The production rate is very high: up to 60,000 copies per hour!

Based on engraving, gravure printing uses a cylinder which is carved out with tiny holes where the image to be printed is supposed to be (which is where the ink is held). Paper is pressed very hard against the cylinder, absorbing the ink held in the engraved holes. Each colour must be printed separately. Gravure printing is widely used for long, high-quality print runs such as magazines, catalogues, packaging, etc.

SILKSCREEN PRINTING This printing procedure uses a screen (first made of silk − where the procedure gets its name. Now pol­yester, polyamide, or even metal mesh screen are used) whose

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fabric is masked or blocked by gum Ara­b­ic every­where outside of the pattern to be print­ed. It works on the same principle as stencilling. The screen is held taut in a frame. The ink is applied with the help of a scraper and passes through the fabric, but only where the gum is not present. Silkscreen print­ing is suitable for numerous printing substrates, paper glass, ceramic, wood, textiles, or plastics. Some silkscreen printing can be done on surfaces which are already in their final form.

INK JET PRINTING This is a digital printing technique, where a line of noz­ zles project ink droplets of various colours, either as a continuous jet, or in pulses. This technique is increasingly used in all kinds of sectors (on all ma­te­rials), allowing the creation of large formats, and has developed the domain of 3D graphics by offering ink jet printing onto surfaces which are already in their final form.

LASER PRINTING Laser printing is similar to the photocopying family of processes (the photocopiers we use nowadays are increasingly just laser printers coupled with a scanner and disguised as photocopiers!). In laser printing, ton­er is used along with finely powdered inks. The image to be printed is digitally converted and projected onto a drum which has an electrostatic charge. The laser beam on the drum creates an inversion of the charge and an image (known as the latent image) of the pattern to be printed is formed. Within the toner, the particles of ink are attracted to the drum where the laser has revealed this latent image. Ink is then deposited onto the paper when it is pressed against the drum. Laser printing gives higher resolution, lower cost (per page), and is much quicker than ink jet printing.

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PAINT FINISHES 1 matt surface 2 satin surface 3 gloss surface

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SOME CHARACTERISTIC PAINT FINISH DEFECTS 1 tight 2 ‘orange-peel’ effect 3 shrinkage cavities 4 holes 5 craters

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Finis­hes All materials. The term ‘finishes’ brings to mind both the question of protection, and the notion of decoration. Nowadays, finishes are expected to extend their traditional functions: tactile effects (softfeeling); supply functions; electrical conductivity, or insulation can even be obtained. Some materials (wood, metal) have trouble withstanding thermal and chemical attacks, humidity, mould, rust, UV rays. Other, more modern materials, like stainless steel and plastics, for example, integrate their finishes (their protective capacity and their colour, for example) into their actual constitution. Industry has a tendency, however, to choose materials predominantly based on their economic properties: effectively, finishing processes are often long and expensive. The surface to be treated must be carefully prepared to ensure the adherence and durability of the finish or decoration. They may need de-greasing with a solvent, sanding, sandblasting, shot-blasting, flaming (passing the surface over a flame) or covering with a layer of primer. Putting a finish or decoration onto a surface has proven, above all else, to be a problem of chemical compatibility. Polyethylene, for example, does not do well with many decorative products; teak and other oily woods do not varnish very well. Finishes and decoration consist of either impregnating the matter with oily substances; leaving a layer of polymer film which acts as a protective screen (paint, varnish); covering with metal (zinc or chrome); or sticking down a related material (bonding of skins, of textiles, and stickers.) There is a wide variety of ways to apply finishes, from hand application (with a cloth, paint brush, large brush, roller, spray gun, or dip-coating) to industrial procedures (electrolysis, in-mould deposits, spraying, powdering, spreading and calendering). Nowadays, the finish and decoration of an object poses a major problem: that of recycling. Indeed as the resistance of the surface treatment depends on the degree of intimacy between heterogeneous materials, recycling often proves extremely difficult. Separating elements joined in such a way is not always easily done. It is therefore necessary to consider this question during as many stages of the design process as possible.

PAINT Paint is a mixture of various constituents: • Binder: 10 to 40% of the composition. The binder is often a polymer resin which ensures the cohesion and final resistant properties of the painted film. When we watch paint drying, we are actually witnessing a polymerisation of the resin binder which begins when the solvent evaporates. Some paints need to be mixed with a catalyst. • Pigments: 5 to 40% of the composition. These give the paint its colour and are either of mineral (metallic

pigments) or organic origin. Pigments can be distinguished: some are coloured particles in suspension within the mixture, and some are colorants which mix more fully, and as a result create the effect of transparency and depth of colour. There are also now pigments known as ‘effect’ pigments, which are used to create paints with coloured sheens which change according to the angle of vision (bluebottle effect and pearlescent pigments) or according to the light (phosphorescent pigments and fluorescent pigments,etc.) • Additives: 0 to 70% of the composition. Silica, chalk, kaolin, talc, and carbon additives give greater cover-

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age, limit shrinkage during the drying process, and mattify the mixture. Additives, always in small quantities (less than 5%) are various chemical agents: thixiotropifiers (control viscosity), anti-streaking agents, wetting agents, anti-rust agents, UV absorbers, insecticides, fungicides, flame retarders. • Solvents: 15 to 35%. These can be volatile, waterbased (aqueous solution), white-spirit-based, or others sub­stances which make the binder workable and give it the correct viscosity. They can also be used to clean the tools. Their end-role, to disappear by evaporation (drying process), is the subject of increased attention due to ecological issues. Continuing to evaporate long after the drying process, they can be toxic. According to the mixture (viscosity), the speed, and the distance of application, a taut surface can be achieved, but defects (bubbling, specks, orange-skin effects, for example) are known to occur. It is common to apply different layers of paint, each offering a different function: a keying layer, an anti-rust layer, a visible layer and even, to finish, a layer of varnish. The majority of paints come ready-mixed in their solvent: urethane, cellulose paint, glycerol-phtalic paint, poly­ and epoxy. For environmental reasons, there is a tendency to limit the number of solvents in use. A proportion of dry extract in paint is preferred (some­times up to 80%), this can cause problems for implementation and appearance. Some paints are available as ‘powders’, and do not contain any solvent. These paints − polyamide, PVC, polyester, epoxy, acrylic − are laid as one single layer and undergo firing at quite high temperatures, which limits their use to only metallic workpieces. This economises on matter; implementation is simplified, but the mastery of surface effects is not always as good as with classic paints.

VARNISH Varnishes are like transparent paints. It is necessary there­fore to distinguish between varnishes and stains in the treatment of wood. Varnishes aim to make a protective envelope and make the wood water-tight. The slightest impact can cause a ‘breach’ and jeopardise the efficiency of the protection. Stains work by impregnating the wood, often with alkyd resins, which are absorbed by the wood and do not form a continuous film on the surface. They ensure a permanent exchange between the matter and its surroundings: the wood continues to ‘breathe’. However, stains are less efficient and much less durable than classic varnish (as a rough guide, they last for about one year outside). Stains, like varnishes, can be coloured to create a ‘transparent’ tint to the wood. In terms of maintenance and upkeep,

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stained pieces can be quickly and lightly sanded before recoating, while varnished pieces need stripping before re-varnishing. Varnishes, often associated with wood, can also be used on metals, leathers, paper, cardboard, plastics, paint, and of course our nails!

ENAMELS AND GLAZES Enamels and glazes are vitrifiable products − often in the form of a powder − applied by fusion (minimum temperature of 500°C up to 1,500°C); they are the same family as glass. Enamelling (a vitrification proc­ess), of a mineral-based substance, gives a strongly scratch-resistant, temperature-resistant, and chemically resistant finish but is not always shock-resistant. Enamels and glazes are generally applied to ceramics and metals (steel and cast iron, for example). Enamelling vocabulary includes: • Glossification: The point when a layer of transparent glass appears during the firing of stoneware and porcelain. • Glaze: A layer of transparent glass which is put on to earthenware, for example, then fired. • Enamels: Coloured or opacified glass put onto ce­ ramics or metals then fired. • Varnish: A very thin layer put onto ordinary pottery when fired.

ELECTROCHROMING Electrolysis consists of chemical decomposition due to the effects of an electric current. An anode and a cathode are placed in a tank filled with a solution, and linked to a continuous current generator. The anode is the positive terminal, and the cathode, negative. The anode undergoes reactions of oxidation, and will loose electrons, whereas the cathode undergoes reactions of reduction and gains electrons. By electrolysis, pieces of plastic can be coated in chrome, nickel, and even gold. The metal is deposited in the solution and the plastic pieces need to be made conductive (ABS, polypropylene, polyamide, polycarbonate, for example). The pieces, submerged in the bath, act as the cathode and will be covered in the metal on all surfaces. It is possible to make quite large pieces (for cars, for example).

FLOCKING Particles of textiles are propelled onto a glue covered surface, creating the appearance of velour. The fibres

can vary in length, be oriented after spraying, and dyed, etc offering numerous variations in visual and tactile effects: velvety peach skin, fluff, faux suede. Flocking can be done on all sorts of materials (paper, cardboard, wood, metal, plastics), with one of its main areas of application in packaging.

and resistant to actions such as abrasion. The material is grey or black. Lighter anodising (layers of a few microns up to tens of microns) protects alumin­ium but can also, with the use of colorants, give varied coloured effects. Anodising is an extremely common protective and finishing technique.

LAMINATING

VACUUM SUBLIMATION

A certain type of laminating concerns plastics. A decorative printed sheet is thermo-glued onto a panel of compat­ible polymer (ABS, polystyrene or PMMA) then the whole thing is thermoformed, folded, or bent into shape. Plastic laminating is widely used in packaging and for bottom-of-the-range products.

A flexible or rigid film, printed with the desired decoration, envelops the workpiece. The whole piece is then put in an oven (at approximately 200°C) where the inks sublimate and transfer onto the matter wherever there is contact. Plastic pieces whose composition can withstand a few minutes of relatively high temper­ atures (polyamide, polycarbonate, POM, for example) can be decorated using this technique.

VACUUM COATING Vacuum coating is a procedure where plastic is coated with metal without the need for heat. A fine sheet of met­ al (often aluminium) is sublimated (turned from solid to gas) in a vacuum and the metallic particles are attracted to the surface of an electronegative substrate such as ABS, PMMA, or polystyrene which has been varnished. This procedure is used to metallise the inside of cars headlights or foil survival blankets.

ELECTROPLATING Electrolysis, can also be used to cover metallic pieces. Electroplating protects against corrosion and gives beautiful metallic finishes (gold, nickel, tin, lead). This procedure is often used on jewellery, plumbing, and in the automotive industry. Electrolytic deposits can also be used to cover steel with zinc (this is known as galvanising) to make the metal rust resistant. Steel is placed at the negative terminal (cathode), and zinc is used as the anode. Zinc ‘transports’ itself to the surface of its steel companion. Alternatively, the galvanisation of steel can also be done by dip-coating finished items at hot temper­atures.

HOT MARKING A plastic film with metallic deposits is inserted between a heated die punch and the piece to be decorated. The pattern, machined in relief on the die, is transferred by pressure and heat onto the piece (which may be plastic, for example). This procedure is fast, simple, and economical. Hot marking is often used to obtain ‘gold’ and ‘silver’ logos on cosmetic cases or flocked packaging. Gilding (with gold leaf) when done on luxury leather objects is similar to this technique.

IN-MOULD PROCESSES Printed tickets and labels can be deposited at the bottom of an injection mould. The label’s matter must be compatible with the polymer to be injected. This technique is very reliable, and is used on the keys of computer keyboards, for example. The close bond­ ing of the materials ensures good resistance to wear and tear.

COATING ANODISING Electrolysis in acid increases the natural layer of alumina at the surface of aluminium which protects it from corrosion (this is known as passivation). In anodising, no external matter is added but oxidation of the sub­strate occurs. Various types of anodising can be distinguished according to the thickness of the layer of alu­mina created. A ‘hard’ anodising thickness (approximately 100 microns) makes the surface of the aluminium very strong

Coating is mostly used in the textiles industry. The surface of textiles can be covered − by calendering, scraping, immersion, or spraying − with a plastic film which makes it water-proof, stain-resistant, shiny, etc. This is a textiles finishing process. For other printing substrates (plastic, paper, glass), the word ‘coating’ is used to describe the covering of a flat surface with a substance which is often liquid or paste-like during application.

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DIP TRANSFER The procedure of dip-transfer printing consists mainly of printing a decoration onto a film which is soluble in water. The piece to be decorated (plastic) is introduc­ed into a bath of tepid water, with the printed film depos­ ited at the surface. Once the film has dissolved, the inks stay in suspension and deposit themselves on the workpiece which is mounted at the surface. Work­pieces can be quite complex and three dimensional. The anamorphosis effects created by the specific geom­etry of the workpiece can be calculated beforehand, and as a result compensated for in the distortion of the decoration. Once out of the bath, the workpiece is dried and varnished.

SANDBLASTING / SHOT-BLASTING A spray gun, inside a closed cabin, propels abrasive particles at high pressure: metallic shot – for shotblasting – or ceramics and sand – for sandblasting – broken peach or olive stones can even be used to obtain a roughened effect on glass, textured surfaces on metal, and a ‘drift wood’ appearance on wood. The process of sand-blasting or shot-blasting can precede some finishes (to prepare a surface to receive paint, for example) or constitute a specific surface state in itself.

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RECYCLING

A classic example: PET bottles are disposed and sorted to be recycled in the fleece sweatshirt production.

Recycling All materials. Recycling can’t be called a production process, as it’s really a set of techniques for processing materials at the end of the life they were intended for, with the aim of re-using all or part of them. In the context of exhaustion of certain raw materials and the ever increasing volumes of waste materials, recycling becomes ever more important. It is evermore considered as a transformation process in its own right and there is even a trend for some designers choosing to work only with materials in their ‘second-life’. The art of economising in material by re-using it in manufacturing, ‘new from old’ one might say, is far from being a recent idea. Throughout history, mankind has had to manage resources, perhaps even more intuitively and effectively than today. Waste treatment strategy may be described by three main principles: • Reduce: Minimise waste in production, for example by reducing packaging. • Reuse: This is where the concept of a ‘second life’ for products comes in, giving them the possibility of continuing in their original function (by repairing them for example and putting them up for sale again) or finding new uses for them in another role. In the second case, the term ‘up-cycling’ is sometimes used. Old plastic bags become mats, clothing becomes chairs, bike inner tubes become wallets, etc. • Recycle: By collecting, sorting and treating waste to be able to reintroduce materials into an existing manufacturing cycle. An example is the manufacture of glass bottles using recycled bottles. Another is the collection of water or other soft-drink bottles made from PET (polyethylene terephthalate), allowing this plastics material to be used in other fabrication processes such as polar fleece garments (commonly referred to simply as fleece). Various recyclable materials (thermoplastics, aluminium, etc.) are now marked with a logo representing a Möbius band. The proportion of recycled material in the makeup of some products is sometimes shown. Some pictograms can evoke the recycling principle (such as the European Green Dot) but don’t have any precise indication of a material’s recyclability, so it is necessary to remain vigilant.

RECYCLING IN PRACTICE Three major types of materials recycling can be distinguished: • Chemical recycling: Wastes are chemically treated in order to separate the various constituents. • Mechanical recycling: Wastes are treated mechanically by machines which may beat, pulp, grind or crush them. • Organic recycling: Suitable wastes are composted to produce fertiliser compost or fuel (biogas for example).

Before going through one of these transformations, wastes have to be collected and sorted selectively. Even if consumers or industries are invited to separate their wastes before collection, it is usually necessary to organise secondary, more precise, sorting (mechanically and manually) before proceeding with recycling. Certain materials even go around the recycling loop several times. The quality of products using recycled materials is generally conserved but may, in some cases be lower than that of the original. It may even be improved when recycling operations also open the

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door to chemical mixtures which improve the properties of the recycled materials. All recycling methods are not in place in all countries. Some wastes will therefore be stored while waiting for conversion or incinerated (with energy recovery from combustion) but the release of dioxins in this process must be monitored with particular care. Wastes that are dangerous for human health or the environment, existing in large quantities in industries and elsewhere, call for specific techniques. Recycling of a material sometimes proves to be simple and cheap, but sometimes very complex and expensive. It is therefore not always profitable (separation of various constituents may be labour-intensive, dangerous, etc.). It’s also necessary to be careful and check that the recycling technique used is not more energyintensive than transforming the raw material: for example, in the bleaching of recycled paper this aspect should not be ignored.

Strong points: waste reduction, preservation of natural resources, alternative source of supply. Weak points: logistics (collection, sorting, etc.), profitability has to be assessed.

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& THINK DIFFERENT

REFLECTIONS ON HYPERCHOICE p.337  / ABSOLUTE LUXURY p.339  / FUZZY LOGIC, FLUZZY TIMES p.340  / FINISHED MATERIALS, UNFINISHED MATTERS p.341 / TECHNOSCIENCES AND DESIGN p.343 / SUSTAINABLE PREJUDICES p.345 / NANO-THIS, NANO-THAT p.358 / DE NATURA MATERIAE p.361.

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Reflections on hyperchoice The middle of the 20th century saw the beginning of a new material era. This expansion rocked the old and thriving world of matter. Each society and period portrays its main images in a particular type of matter: the Middle Ages set their eternity in stone, the modern era cast its excesses in steel, but contemporary society seems to have really rocked the boat and caused a frenzy of materials dubbed ‘new’. However, if we look more closely, the crux of the matter actually lies in matter. We are still working with the same old atoms; the very same ones in fact, which Mendeleyev recorded in his everfamous periodic table of elements. When matter is described in this way, it seems to be a finite group, but this table of atoms, laid out as a mechanic would spread out his tools and parts, was also the starting point for the new and infinite world of materials which we pick, choose, and combine to produce increasingly high-performance materials. To better understand the situation, we should distinguish between materials and matter. Hegel paradoxically tells us that matter ‘is something purely and simply abstract’ and that it is inextricably paired with a predetermined form. This is the unfathomable mystery that each epoch attempts to explain and which can be seen today in the concept of an immaterial society. Perhaps ironically our ‘immaterial’ society has never produced so many new materials before. This boom of semi-products is launching us into a vortex of ‘hyperchoice’ where the plethora of goods on offer is becoming impossible to comprehend, define, or record at a single glance. From amongst the multiple causes of our current situation of hyperchoice, there are some which stand out as key. Firstly, we have moved away from the situation where one person, one knowledge set, controlled the entire production process of an object. A craftsman’s world has become a world of industrial operations and engineers. Each problem is isolated. This conceptual segmentation leads to the fragmenting of processes; each stage representing a multitude of possible solutions and trade secrets, and therefore a multitude of interchangeable material responses. The outcome of this compartmentalism is a transfer of technologies, which has become a creative method in itself and a tried and tested factor in innovation (and also in the development of ideas). In fact, what we are witnessing could be called a de-specialisation of matter. Secondly, a large part of current scientific research has lost its independence from production. Nowadays industry allocates considerable funding to vital research and has developed a dedicated sector: R&D (Research and Development). The advent of what are commonly called ‘techno-sciences’ has greatly shortened the time lag between the discovery of a material and its application in industry. Nowadays, there are materials being developed which do not yet even have an application. Thirdly and finally, the changes in our industrial societies have totally confused our relationship to the natural world. Technology has long been a shield against nature, which was considered hostile. Nature was something to protect oneself against, something to withstand. This rather violent understanding is now somewhat reversed. Faced with a nature now seen as fragile, our model has become one of cooperation. We now see 337

ourselves as participating in natural models. Nature doesn’t pursue any one single solution to an obstacle, but rather forces many responses to cohabit and even compete together. By learning to expand diversity in this way, wherever technological reasoning would have been inclined to seek one single, perfect answer, we are actually adding to the situation of hyperchoice. A catalyst to this phenomenon is indeed the globalisation of exchange (of both information and merchandise) which has put a growing number of instant-access reference resources on materials within everybody’s reach. Consumer society, with its characteristic extreme competition, hinging on an incessant remodelling of markets, also contributes to hyperchoice. This remodelling occurs when the massive impact of having a range of products causes materials to go out of vogue at the drop of a hat and to be reborn under increasingly diverse forms. Our industrial societies are, without doubt, undergoing a transitional period. The classic reasoning which surrounds matter; the shared and traditional perception which we had of it, in terms of classification, (e.g. wood, metal, plastic, etc.) is becoming more and more defunct. The constituents we work with fall increasingly ‘between two columns’, they are unclassifiable and blur the lines of identification of matter. Materials imitate each other, compete with each other, replace one another, and thoroughly confuse us! It is becoming ever more urgent and necessary to create new categories, to think of matter in other ways, and probably to describe it in terms of purpose above all else. Matter no longer imposes its constraints on objects as it did before. It is more purpose, which dictates to material, sometimes even leading to specific reformulations of matter. Transparency, lightness, softness, intelligence of matter: so many new entries to the lexicon of properties, all vying for a new materials’education, focused on complexity, on fundamental physical and chemical properties and on political issues, out of which the new categories will rise. For an updated idea of technology.

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Absolute luxury Luxury has always been the prerogative of the Great, the supplement of the soul and the mark of definitive superiority. This supplement to the soul however, is quite often proved to be a supplement of matter; an excess of those rare matters which have always been inseparable from the economic and social ties which are exactly the things which give them their value. Throughout history, the conquest of unknown territories never failed to bring home new materials which forged difference and brought the subtle idea of luxury: precious metals, stones, marbles, amaranthine, ebony. Their shine, their purity, their transparency, their depth, and their unchanging hardness have one after the other, or simultaneously, played the role of the embodiment of the absolute. Minuscule crumbs of one matter in particular are the centre of considerable attention: gold. Gold has been, and remains, the material which unites all the ingredients of fine and inextricable alchemy. Unchanging and brilliant, malleable and rare, but available in just sufficient quantities to satisfy this urge to differentiate oneself. This is perplexingly coupled with the need to fit in, ‘to be different, just like everybody else’. A complicated and finely balanced condition continually achieved only by a select elite of materials. However, all these luxurious materials which have traversed the centuries in knowing and peaceful assurance now find themselves flung into our modern societies; bringers, with all the good intentions in the world, of the values of affluence and democratisation. Our consumer society has turned luxury into an industry, which from the 19th century onwards subjected itself to an explosive acceleration, resulting in severely depleted material stocks. In today’s Western societies, aluminium, titanium, precious transparency, and purity have all gone from rare to ordinary at lightening speed. The sparkle of bronze, the patina of leathers, and the luminescence of tortoise shell have all tarnished under an avalanche of imitations. And all this to such an extent that luxury is now even sold in hypermarkets, with a worrying number of professionals (cosmeticians, luggage vendors) living in fear to see luxury dissolve as it is reproduced. In the affluence and popularisation of the product, what sign, what material can still truly bear the mark of luxury? Logos, brands, and signatures have replaced the traditional marks of quality. Perhaps then, it is the materiality of luxury which now finds itself called in to question. Gold, the supreme embodiment of value in a material, is now threatened by monetary value (the dollar), king of the market, a virtual object which is no more than a ‘potential’ with no fixed form, but which can endorse anything! With this kind of dilution occurring, how can the idea of luxury survive? Can it reincarnate itself outside the confines of material? Can we imagine a virtual luxury, deprived of its sensory attributes? How will the matter of tomorrow deliver luxurious escapism?

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Fuzzy logic, fluffy times Stretching itself out on the cushions of consumers’ desires and in creators’ expressions. A paradoxical notion, vehicle of a firmly pejorative connotation, softness, is now becom­ ing associated with recurring images of comfort, of sensory proximity and attention. This U-turn is perhaps a sign of an underlying movement in the world of matter. Often defined as an opposite, being soft (‘not hard’) has become a sought-after quality. Soft-to-thetouch keyboards and other ergonomically designed controls, shoes, and even automotive interiors, use flexible and casual shapes, and reactive materials such as ‘memory’ foam or medical gel. The value of ‘hardness’ in a matter has always previously represented the ideal of scientific and technical development. There is no ‘Soft’ Age listed in the history books between the Stone Age and the Iron Age, despite the fact that soft materials did exist even then (rubber trees, pelts). Charles Goodyear and his stable rubber of 1839, mark the beginning of the industrialisation of ‘soft’. An intermediary state par excellence; neither solid, nor liquid, ‘soft’ has never deserved much scientific attention before now. Scientists were always far too busy studying those states of matter deemed ‘fundamentally noble’. New areas of exploration are now tentatively opening up, into this transition between phases, a more adapted-adaptive response. Is this perhaps a fourth state of matter? A highly ambiguous state, it provokes attraction and repulsion, sparks irrepressible tactile temptation and hides unexpected depths. Nasty or nice? Softness fascinates us because it is reminiscent of life. It brings to mind body, flesh, and sensual pleasures. Softness oozes and trickles; it spreads. It relentlessly takes us toward its very own end and ours. Indeed, softness changes. Foam polymers, gels, and silicone will all crack one day, some even end up hardening! But we are no longer living with the same relationships when it comes to time and matter. Once ever-lasting, objects nowadays have inferior life expectancies. Softness is all a question of scale: time, size and temper­ ature ranges. We are always soft when there is something harder around! Softness is a perception, and ultimately, it is relative. Gulliver would have slept perfectly well on a slab of steel whereas the Princess doubted the softness of the mountain of mattresses, which was all that protected her from a tiny little pea! Is the emergence of softness a translation, in material terms? Is it a detachment from the ideological and technological certainties of Western societies? Are we beginning to doubt absolute answers? It seems that nowadays we demand more from materials than just technical solutions: we demand intelligence and sensations. Above and beyond softness, perhaps we have entered into a relationship with matter which marks a turning point in the era inaugurated by the industrial revolution.

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Finished materials, unfinished matters Finishes. What a strange semantic paradox it is to think of objects or buildings as ‘finish­ ed’ just when their life cycle with the user is about to begin. Long seen by humans as an external reality, objects are now hurled into technological and scientific torment, called into question, and scrutinised, that which seems ‘finished’ today, is actually only one particular vision of that object. Finishes are commonly seen as the shell, the surface state, or the final layer placed on matter. This particular notion of finishes is now being replaced by the idea of interface, of skin; the man/object relationship is being thought of in a new light. Finishes traditionally followed the motto ‘to protect and decorate’. These two functions have co-existed, and counterbalanced each other in a complex way, varying according to the trend of time. During the refinement of the 18th century, decorative function was dominant: it didn’t really matter what the core material was, as this would soon be covered up. Was this the apex of decorative art? Dainty motifs sporting shepherds and shepherdesses, floral patterns, etc. Objects became a narrative aid above all else. The protective efficiency of these finishes is nearly always very low, just like white-wash paintworks which have to be applied and re-applied every year. During the 19th century, the industrial era, it was protective finishes that gained influence. The development of functionalism often reduced matter to its most neutral state possible. Protect, level and flatten the characteristics, until plastic appears, the archetypal inert and functional matter (no past, no history). The pleasure of decor fades. It can only survive if it sets off the function or if it fulfils some commercial purpose (hence the advent and omnipresence of logos as sole decorative agents). The finish of an object will also serve to persuade us of the matter’s permanence: the illusion of absolute protection can be created by chroming, for instance. However, it is note-worthy to observe that between protection and decoration, in the world of finishes, there is a recurring theme of imitation. Finishes know how to disguise something poor as something rich. Plastic, here too, is king. In fact it was through imi­­t­ation that plastic first gained its rank amongst the materials. From the ‘70s onwards though, even the very idea of finishes seemed to be turned upside-down. Was it a loss of confidence in the values mobilised by the industrial revolution? Or was it a protest against consumerism and so-called miraculous technology? Whatever the reason, ‘nature’ made a big come-back, and no more so than in the awakening of our consciousness, a realisation that it would be vain to try and dominate nature. Objects lose their protective shell little by little, they walk hand-in-hand with us and we accept their aging. It was from this point onward that ‘natural’ materials (wood, leather, and stone) gained vigour, and their finishes allowed them to ‘breathe’. Tints, patinas, and protective oils made an appearance. Coatings became more and more discrete and finishes were confined to the realm of the cosmetic. Through this return to the fundamentals of matter, the very status of objects has been called into question. Their frontiers are now so flexible, they are zones of interaction with man, and objects have become the artificiality which completes the dialogue with nature. The idea of 341

‘skin’ takes precedent over that of ‘finish’. ‘Skin’ calls to mind contact via the senses, it implies ‘pore-osity’ and interaction. Emerging technologies (chemistry, physics, and nanotechnologies) are participating in this evolution. Breathable-waterproof textiles and membrane coverings, foam with integrated skins, retardation effects, communicating and conductive skins: liquid crystals, thermochromic or photochromic pigments. The ‘surface’ of an object is now a zone which responds to external demands rather than resisting them. Moreover, from the inside of the objects now comes various fluxes – such as heat, for instance – information that the skin is brought to treat and deal with. This more and more important skin seems to even provide the object’s function. Analogy with living creatures is getting closer and closer. We are entering the complex and subtle ‘Inter’ Age: interaction, interface. An age where matter will produce its own surface treatment, will know how to self-heal or oxidise to regenerate (like Indaten steel), and will go as far as to create virtual matter. 3D computer-aided design of objects and architecture often undergoes a basic ‘skin construction stage’, without the need to worry about the bones of the structure in question. But can we, and should we, really reduce an object to nothing more than its skin? Such are the questions raised by new design technologies.

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Techno-sciences and design The links maintained by creative professionals with the world of science have fluctuated over the course of time, from sometimes wide-eyed fascination to the greatest mistrust, and even veering toward disdain. The emergence of design as a discipline has marked a renewed interest, almost a direct line of descent, between the technical and creative fields. Design at the end of the 20th century is, for the most part, mixed with heavy technological practices and mechanical reproduction. The advent of what can be called techno-sciences has confirmed creative professionals’ attraction to ‘new’ materials, lighter solutions, and high-technology. In The Material of Invention: Materials and Design, Ezio Manzini describes the intermingled destiny which links design and engineering technology. Technology was then witnessing an explosive acceleration, a systematisation, a rationalisation, a miniaturisation... The rules governing the making of objects, however, still obeyed the same laws, the same technical logic, only pushed to the point where they were able to multiply performance. The 21st century is undeniably opening onto a new order. The shaking-up of work practices is mainly characterised by a radical change in scales. Change in the scale of observation, which is nothing new, but more importantly, change in the scale of intervention possibilities, in particular, intervention into everyday objects. Science took the lead over the purely technological component in the techno-science duo. Exponential progress in the fields of physics and chemistry today allow us to manipulate matter, not just on the outside, but also on the inside. This micro, even nano, outlook has created a totally fresh field of intervention. More astounding, and yet part of this reality all the same, is the fact that matter does not necessarily act in the same way at both macro­scopic and microscopic scales. This leads matter to behave in unexpected, foreign, and unobvious ways which are at odds with our usual codes of perception. In just a few decades we have shaken off the old conceptions of inert matter in favour of the idea of intelligent matter. The industrial revolution, largely founded on the practice of mechanics, is a spectacular manifestation of the way we saw matter during this time. When we see a motor firing, we can distinguish quite easily between that which is due to the qualities of matter, and that which is due to human genius. The contrast between matter and function is clear. The idea of intelligent matter blows these categories out of the water and places function at the heart of matter. A simple little black box may turn out to be a telephone, a razor, a camera or a nutrient (a nanometric object only measures a few hundred nanometres, the naked eye is only capable of distinguishing objects from 10,000 nanometres upwards) which muddies the water even further. We have all known the time when machines – miniaturised – have disappeared inside boxes. But now we are entering a time where there will be nothing anymore inside the box, because everything will be contained within the matter of the box itself (if we’ll still call it a box). Born from this idea of function loaded into matter, is the connection which scientists have graft­ed between inert matter and biological matter, by copying living systems: molecular micro-machines, active and selective 343

membranes. Joël de Rosnay, defines intelligent materials as being characterised by three criteria: sensitiv­ity, adaptability, and the ability to evolve. These materials possess functions which allow them to behave like sensors – signal detectors; actuators – which can produce an action on their ‘environment’; and sometimes processors – which can process and store information. They are therefore capable of spontaneously modifying their physical properties such as shape, visco-elasticity, or colour, in response to external, or internal, demands. In the field of industrial and architectural product creation, the issue arises of how to bypass the ‘gadget-isation’ stage of intelligent matter, in order to pose the underlying questions which maintain and renew the old dogma that function must precede form. This intelligent matter has, by nature, disappeared into objects with no form. This dilution could lead one to think that everything can be contained in everything; light or sound might surge from any form or matter. If matter can take on many forms, which form should an object or ‘thing’ take? It is not by complete accident that we have seen a resurgence in the contemporary creation of decoration as the definitive sign of meaning. But under what conditions should this pattern re-emerge? How do we rid ourselves of the ornamentalist voices of the 19th century? We are now seeing images and motifs from scientific drawings reappear. Many young creative profession­als and contemporary designers are using microscopic images from the depths of matter, showing us rhizomic structures, and tirelessly re-questioning the boundaries of an object, inter-object reactions and skins. These are the lines of enquiry to which our physical and chemical world subjects us. An omnipresent but untouchable world, yet everywhere subjected to questions and attentions which it perhaps does not right­­ly deserve. It is the young creative professionals responsibility to deal with these enquiries. The renewed image of science as a land of adventure is not just a nerdy dream: our representation of matter also depends on it, full of possibilities as well as submisions. Merleau-Ponty said: ‘science manipulates things but gives up haunting them’. This is certainly one of the major challenges facing designers, if design wishes to progress on the pathway to creation.

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Sustainable prejudices How can we talk of matter nowadays without mentioning ecology in the same breath? Sustainable development, eco-design, ecological labels, fair trade, High Quality Environmental standard (HQE) often boost the headlines of glossy magazines (and sometimes even boost some bottom lines too); the exhaustion of our fossil fuel re­serves, the greenhouse effect, global warming, and threats to biodiversity are a source of worry for some, a reason for others to make new years resolutions and can even provoke political activism in some. These worries, which mostly affect societies of the developed world, show us that industrial development, as we experienced it, is no longer possible, particularly if China and India, for example, want to join the game too. The reactions to upcoming imbalances (ecological, social, and economic) reaffirm the supremacy of Mankind and the need to preserve our environment in order for our race to continue. These questions obviously ring true in the fields of matter and materials but the issues are far more wide-reaching. However we are constantly confronted with choices of materials and the question of standards of performance is all the more prevalent. While, once upon a time, the need for speed pushed us forward; nowadays, it is energy consumption which motivates us. The arrival of information technology has allowed Mankind to use powerful tools and work with very little energy. This has pushed us to develop intelligent materials capable of using their own intrinsic resources to move and transform without an external energy source. It is becoming just as crucial to no longer think of objects as autonomous entities, but as elements of matter undergoing transformation in a life cycle which will eventually come full circle: from raw matter to manufacture, distribution, usage, and recycling. Many industrial sectors end up being not only responsible for the production of a product, but also for its obsolescence and disappearance. In this context, there are no good or bad materials, as many would like to think, but simply many long-lasting prejudices. Industry has long led us to believe in one ‘material’ solution which conditions matter for a certain application (while stocks last!). This concentrated exploitation inevitably makes mining and extraction operations reach ‘critical mass’ which can prove dangerous (asbestos, uranium, plastics, CO2). It is now becoming necessary to rethink the entire production cycle of industrial goods, it is time to move towards sensible and planned diversification; using the sum of resources under threat balanced with the sum of our needs. We are now seeing the rebirth of older methods of production for polymers from non-petroleum products (vegetable, animal); the appearance of new materials, produced directly from recycling (some channels of recycling are now at the forefront of development); energy sources are diversifying into wind power, solar power, and maybe even nuclear fusion. The solutions which must really be implemented are actually political rather than simply technological. Our capitalist and industrial economy seems to find elements of viability and market potential in the exploitation and development of these sustainable aspects (new jobs, profits). This is actually reassuring, since although this awakening of consciences was slow to begin with, it is now well and truly on the map. Will the geopolitical balances of this planet – which are precarious to say the least – be capable of handling these questions? 345

Nature versus nurture The infamous arch-enemies, ‘natural’ and ‘artificial’ are two distinctions which are commonly and obviously applied. Most people think of that which is ‘natural’ as being healthy, and miles better than all that ‘junk’ found in ‘artificial’ produce. ‘Nature’ evokes tradition and the past. Whereas ‘Artificial’, seems to makes us think more of the future and the unknown. Isn’t it true that whenever we begin to lose our comprehension of something, our sense of harmony with how something works, we give it the attribute ‘artificial’? Upon closer inspection, the boundary between natural and artificial is not actually all that precise. The line in the sand is actually dreamt up and nurtured by the limits of what we find ‘acceptable’. The common definition of ‘artificial’ gives: ‘something produced by the work of man and not by nature’. But isn’t man a product of nature? When man transforms something, isn’t that only nature acting through him? This nat­ural versus artificial opposition is nonsense and infers that man is in fact artificial! The term ‘artificial’ seems to be born out of simultaneous misunderstanding and mistrust. It is when our dictated rules change, through trickery (e.g. magicians who use stage effects), or through fear, that the word ‘artificial’ rears its ugly head. Not to mention the religions where artifice is the work of the devil and palpable anxiety feeds prejudices. Matter is certainly not exempt. However, to fear ‘artificial’, is to fear that which nature can produce. In our minds we contrast natural matter, wood, for example, against artificial and generic ‘plastic’. But is there really that much difference in what separates a tree from a chair and crude oil from Tupperware? In both cases, the natural resources have been worked by man. This is what Ezio Manzini describes, in his reference work The Material of Invention: Materials and Design, as the thickness of artificiality which actually seems a far more apt way to characterise matter: by its degree of transformation. Why does plastic seem more artificial to us than wood? Perhaps it is because it never underwent an ‘artisan’ phase. As it was immediately industrialised it eludes our knowledge-base and our understanding, once again. So a material is considered more natural if it has been embedded in our collective culture. However, matter is the framework of artifice and materials are natural artifices. We were condemned to artificiality from the moment man first walked the Earth. Essentially the question is not one of natural versus artificial, but rather to what ends we use artificial substances. The most important thing for our generation to remember when it comes to matter, is to increase education, learning, and collective knowledge so as to avoid clichés and allow the debate to rise to the level of real issues. To name but a few, those famous ecological questions linked to matter, where hotchpotch ideas and prejudices intermingle to create confusion and well-meant but counter-productive action. ‘Artificial’ must remain the reasonable (rational, intelligent) exploitation of the tremendous potential that nature offers us. We must certainly resolve to enter into a situation where complex technological culture can be shared in order to evaluate, amongst other things, real threats. Virtual matter is perhaps the only true artificiality of today: that which leads to folly and distances us in a very real way from our privileged relationship with nature. 346

ECO-DESIGN Designing either a real or virtual object puts into practice many principles and mechanisms, and calls on people, material, energy and technology. Each stage and each decision means weighing up ecological and economic and social factors, the three main aspects of sustainable development. Designers therefore have to take care over the choices they make. To go for solutions which, while maintaining its performance, minimises the impact an object has on the environment throughout its life cycle, from extraction of the raw material to the end of a product’s life. Such are the objectives of eco-design. Although the choice of materials and technologies influences the life cycle of a product in a significant way, these are not the only parameters to be taken into account. One unfortunately often finds, that so-called ‘ecological’ reasoning only goes as far as the choice of well-known ‘natural’ materials, so the choice is simply ‘greenwashing’. Caution is essential, every decision has consequences. We devote ourselves to a precarious balancing act: a material from renewable resources could in the end result in a higher consumption of energy for its transformation, more discharges into water, more noise nuisance, more countryside destruction, etc. There is no perfect answer, but multi-criteria studies will help us in our choices and improve the performance / environment ratio of products. Two approaches can then be seen: aim for an increase in the usage value or reduce impacts. These thoughts are particularly relevant if they are made early in the design process.

REGULATION More and more regulation is being put in place in each country and also at the European and global levels. Finding one’s way through the directives, standards and certifications, as well as their updates and evolution is not straightforward and local disparities in terms of requirements make the task no easier. There are directives imposing measures concerning the collection of used batteries, others for the recovery and treatment of refrigerant fluids, etc. In the field of packaging, various directives have led to the setting up of systems such as the Green Dot, now internationally recognised. However, be aware that it does not necessarily indicate that the packaging in your hand is recyclable and/or will in fact be recycled. The European RoHS directive (restriction of use of hazardous substances), which relates to electrical and electronics equipment, restricts the use of specified substances such as lead, mercury, cadmium, hexavalent chromium and brominated flame retardants (PBB and PBDE). • REACH (registration, evaluation and authorisation of chemicals) is a European regulation with the objective of protecting human health and the environment against the risks posed by certain chemical products. This is a database with information on a substantial number of substances. There are currently more than 100,000 substances •

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listed. REACH concentrates on about 30,000 of them which are produced or imported at weights of more than 1,000 kg. Any unlisted substance will not be authorised. Companies manufacturing or importing chemicals have an obligation to assess the risks associated with their use and to implement the necessary measures to manage these risks. REACH does not cover radioactive substances and wastes. A list of substances giving cause for concern (carcinogenic, mutagenic, toxic, etc.) is regularly updated. Material Safety Data Sheets which are provided with chemical products can/must be required for their use. • EU directive EuP relates to energy-consuming products such as boilers, refrigerators, TV sets, computers, etc. with the aim of ensuring that their energy efficiency is increased and their environmental impact reduced. • There are now requirements for product labels to provide consumers with ‘environmentally honest, objective and complete’ information to make their choice. The difficulty is first and foremost the choice of parameters to be taken into account and then how to evaluate these parameters. To compare products with full knowledge of all the facts is obviously a good idea, but how can you be certain of having taken all factors into account? • Standards such as the international ones in the ISO 14000 family are of interest for environmental management. They are for organisations (in particular for companies) which aim to control their impact on the environment. Certification is provided by an accredited third party. • Communication concerning environmental questions also raises plenty of questions. Promotional documents tend to convince us of the ‘green’ nature of products but they are sometimes (often?) misleading. The labels on some products give us a guarantee that some aspects have been respected, but not always. There are different types: • Official eco-labels, accompanying products and services which are more environmentally friendly than most and which are allocated by an accredited third party, allow us to have some supposedly reliable points of reference. Some countries have their own official eco-label (Canada, France, Germany, Holland, Japan for example) and there is also an official European eco-label. • These reliable pictograms shouldn’t be confused with some company-declared facts which are the entire responsibility of the manufacturer or distributor which provides them. The important point about them is that they are subject to various international standards and must relate to verifiable and accurate information. For example, the Möbius band with thermoplastics or aluminium, indicating some recyclable and/or recycled content (if a percentage is shown), is company-declared information. We should, however, be wary of this company-declared information as it is not always reliable or gives the wrong idea (the aluminium identification pictogram for example, which evokes a life cycle, but finally guarantees nothing on this question, or the famous ‘Green Dot’ previously mentioned). • There are also certifications provided by recognised bodies which are considered worthy of confidence, such as the FSC label (forest stewardship council) or PEFC (program for the endorsement of forest certification) which guarantee that certified wood is from forests managed in a responsible and sustainable manner. 348

All the labels and pictograms appearing on products are not necessarily multi-criteria, that is to say that they are not bound to cover all aspects of a life cycle. Thus, the FSC and PEFC labels are concerned solely with the production and extraction of raw materials and the Möbius band with a product’s life end, while the official eco-labels like European eco-label cover the whole life cycle. • Environmental product declarations can also be established, as eco-profiles that actually transcribe the results of life-cycle analysis of the products considered.

EVALUATION There are different tools (software) and methods in existence for the environmental assessment of products. Various companies specialise in this type of studies, every day carrying out life-cycle analyses, energy reports and assessments to assist designers and manufacturers in their decision-making. There are four main types of indicators: • Impact indicators: concerning the environment, such as the influence on climatic change, the use and therefore destruction of non-renewable resources, etc. • Flow indicators: consumption of water and energy, waste, etc. • Design indicators: the product will be dismantled easily, will be recyclable, etc. • Management indicators: centred on business activity (ISO 14001 certification, percentage of eco-designed products, etc.).

MATERIALS It will have been understood that materials alone can’t guarantee an ‘eco’ product and it’s necessary to consider various criteria. For example, a material like aluminium, the manufacture of which is very energy-intensive, can be called for in some cases because, being lighter than steel it may in the end result in the use of less fuel once it is part of an aircraft or car. It’s all about relativity. For each family of materials that has already been explored, the following is a small, far from exhaustive, list of ideas and good practice. Wood If wood is in essence a renewable raw material, this renewability is neither guaranteed nor immediate. It can take from 60 to 100 years for a seedling to become usable wood. It is therefore essential to pay attention to its provenance and to ensure that it is from sustainably-managed forest (FSC and PEFC labels). Paper and cardboard This family of materials from the wood industry is commonly recycled today. However, the paper industry is greedy for water and recycling is not infinitely possible (fibres 349

gradually become shorter and recycling can’t be repeated more than about five times). Also paper processing, e.g. bleaching, is environmentally damaging. Just as for wood, FSC and PEFC labels now offer some guarantees that should not be neglected. Leather and skin A family of materials notoriously polluting and thirsty for water in their processing. However, in countries such as Italy where these industries are closely regulated, progress is considerable, proving that leather need not be harmful to the environment. Metal A readily-recyclable family, which starts off with a rather favourable characteristic, even if the manufacture of aluminium among others needs a lot of energy. Moreover, the exploitation of raw material resources (various minerals) is constantly increasing, and the exhaustion of deposits is a serious problem. Mining operations are subject to criticism relating to the devastation of landscapes, inhuman working conditions, etc. Glass and ceramics Glass is renowned for being recyclable and is often preferred above plastics materials. However, all types of glass are not recyclable. So-called technical glass, such as that in light bulbs or spectacles, is difficult to recycle. Coloured glass will have to be sorted before being recycled and crystal glass, which has a lead content, is not really suitable. Glass manufacture in itself is very energy-intensive. Plastics Plastics materials are without doubt at the very centre of ecological questions, with fingers pointed at them, often incorrectly. There are two main dangers for the plastics industry: • The predicted demise of fossil fuel, the raw material for polymer chemistry • The problem of plastics waste. A large proportion of this is not biodegradable and de facto accumulates, gradually polluting land and sea. Current research is on two levels. Firstly, the gradual replacement of oil in the manufacture of plastics materials by renewable bio-sourced materials. Secondly, the organisation of the end of life of these plastics, by the establishment of effective recycling chains and the development of types of polymers which decompose naturally without subsequent adverse effects on the world’s eco-systems. However, the complexity of the equilibriums in global eco-systems leads to a number of paradoxes that must not be hidden, such as the negative effects induced by firstgeneration bio-sourced polymers (grain, cane sugar). Large-scale production of these led to tensions on the traditional agricultural food markets, not to mention the intensive land-use, monoculture, deforestation and culture of GMOs. Composites Under the spotlight because by their very nature as composites they are difficult to recycle, they nevertheless open the way for the use of ‘greener’ natural fibres and res350

ins. Their exceptional performance, once a complete study has been carried out, can compensate for their recycling difficulties. Textiles • The production of cotton, although it is obviously a ‘natural’ fibre, is responsible among other things for a major share of the world’s insecticide use. We should promote cotton from organic agriculture. • The textile domain raises some social issues: labour in this sector is often exploited. • Dyes, finishes and treatments - every stage involved in textile finishing is questionable. • Recovery and recycling are being put in place in numerous countries. Stone Asbestos, a naturally occurring mineral has been found to be extremely harmful. Rock extraction damages landscapes, disturbs ecosystems and does not always have the optimum working conditions. Light Many arguments have arisen over the emergence of new lighting sources such as LEDs. Now ubiquitous, it should not be overlooked that their manufacture is not problem-free or non-polluting. The choice of fluorescent lamps against the traditional incandescent lamps is considered in some countries, France included, as a serious error of judgment. Fluorescent lamps are almost impossible to recycle, containing toxic elements, compared with incandescent lamps which give heat in addition to light, are easy to recycle and give a better quality of light. Concrete If concrete is seen as a local product, making use of relatively simple and accessible mineral resources, the manufacture of cement is in fact very energy-intensive in itself, with significant CO2 emissions from the process. Cement producers are making progress and seeking to improve the balance sheet. There are also ways to recycle concrete rubble from demolished buildings.

A BUNDLE OF ISSUES Access to certain fossil fuel or mineral (precious metals, uranium) resources has been a major issue for a long time. Technological developments are making ever-increasing demands on the number and quantity of mineral resources on which our economic activities are based. There is now a belated and painful awareness that our Earth is a finite space, and that it will no longer be able to provide all that our voracious modern society needs. World population has seen almost exponential growth since the industrial revolution, from 1.5 billion people in the early twentieth century to just over 7 billion today. Our lifestyles and therefore our needs have also increased sharply, leading to 351

a gradual diminution of all resources, plant, animal and mineral. Above all, we must remain constantly aware of this new, real and acute constraint of scarcity for some materials (fossil fuels, animal resources) and the relative and debatable scarcity for mineral and vegetable resources. We must develop new, rational management logic for economics and recycling. Strategic issues Today, no country can meet its own national industrial requirements from its own resources and has to go to global markets for some of them. Savings are now dependent on nervous markets for supplies, which may be very fluctuating or even erratic, for what are sometimes essential resources in certain sectors. The strategic dimension of the markets is therefore obvious. Like the situation in the twentieth century in the world’s petroleum market, there could be a decisive advantage, both politically and economically, in having control of certain resources in the absence of easily found substitutes. One example is the war that large industrial groups were involved in during 2011 to control Bolivia’s lithium reserves, the new ‘green gold’ of the energy sector. This metal is essential for the manufacture of high-capacity batteries, a rapidly expanding field, especially for future electric cars. The deposits in the Andes represent over a third of known world reserves. For the relevant manufacturer to hold this source is therefore to secure its supply, guard against excessive volatility of commodity prices over the medium term and ensure they have the quantities needed for production. Another example, this time at state level. Since the 1970s, China, which owns 30% of the world’s rare earths, has considered these minerals to be China’s ‘oil’. Since the 1980s it has therefore pursued a concerted, planned policy to gradually achieve a monopoly position in this niche world trade. In twenty years China, with the Bayan Obo open-cast mines, not being held back by strong environmental considerations and profiting from low labour costs, has literally killed off competing producers by offering the lowest prices on the world market. It now controls 97% of the world trade in rare earths. In the global arena this position is strategic in three ways. On the one hand rare earths are intimately linked to technical innovation. In addition to this they are now essential to military industry and defence, and finally China is pushing rare earths a bit further up the value chain by not only selling these precious minerals but also the finished products containing them. For this reason, international technology-industry factories have a strong presence in China, to be as close as possible to their strategic supplies. The wake-up call for Western countries has been painful and bitter. It’s ironic that China has used capitalist market logic in the short term to impose its strategy over the long term. Economic issues Increasing scarcity of resources, diversity of production markets, with increasing consumer demand and inflexible supply, are all ingredients to make global markets tense and nervous, with highly volatile commodity prices and thus significant economic impacts. Nevertheless, we are witnessing a global increase in the cost of materials, whether it’s wood or other plant material, hydrocarbons, and obviously minerals and 352

metals as well. An example that is often cited because it affects all sectors of industry: the world price of copper has increased tenfold, with major upheavals, between 2002 and 2011. This type of fluctuation in metal prices does, of course, have a very important economic impact on the markets concerned. A major American car producer had a bad experience with it at the start of the 21st century. The world palladium market was experiencing a significant dichotomy between too low a supply and an increasing demand. This resulted in panic on the world stock markets, leading to a surge in prices to record levels. Fearing a shortage of palladium stocks for its manufacture of catalytic converters, this industrial stock was held in colossal amounts of this highly-priced metal just before the price fell in 2001. Result, a net loss of $1 billion which almost led to the collapse of the industrial group. A final example of the strong effect of some constituents on the price of final products: rhenium occurs in a proportion of 5% in the make-up of a jet engine (the melting point of rhenium is around 3,180°C), but it is responsible for more than 80% of the engine’s price, as a material with no possible alternative. Health issues Today, there is another aspect that should not be overlooked in the choice of materials when designing or making an object. That is the consequences of these choices on human health, in any phase of the object’s life, i.e. in the use, destruction, disposal or recycling of the product. The emergence of this issue is the cumulative effect of a growing awareness of the impact of our immediate environment on our health and the increasing number of more and more complex types of materials that confront us every day. New materials for which we do not have the necessary use-experience to judge their potential safety, and we do not necessarily have control over all aspects of their use. This is particularly the case for so-called ‘nano-materials’, a term defining materials that possess special qualities related to their size or their nanometric-scale structure. The toxicological and ecotoxicological risks are related to the size of these particles, their indescribably tiny size promoting dissemination in the air and through mucous membranes or skin, making them very difficult to detect, impossible to filter, stop, or control. The use of nanoparticle silver ions is very effective for neutralising bacteria and neutralising odours on clothes, but then these particles are found in waste water. They can’t be trapped by filters in treatment plants and end up in rivers where their still-effective antibacterial properties eventually damage eco-systems. Today we are witnessing the emergence of many products incorporating nanoparticles. These may have properties offering benefits for our comfort and health, for inclusion in boat anti-fouling materials, etc., but we have to be certain that the cure is not ultimately more dangerous than the disease. Societal issues Because we are implicitly making a social choice when we choose a material, we should make ourselves aware of the conditions under which our chosen products are manufactured. We can’t just ‘look the other way’. Many of our everyday objects and the materials 353

we use are obtained or manufactured under bad conditions, sometimes without regard for the health of the workers or local populations, with violations of local and/or international labour laws and sometimes using extremely low-wage child labour. Choose to use the fruits of this human exploitation with full knowledge of the facts, before giving your implicit support to such systems. In the face of the depletion of resources and all the problems caused by human activity, our way of looking at the world and our place in it has to change. We have to accept the complexity of our planet Earth and its fragility, try to work with it rather than against it, change course and learn to manage scarcity, moderation and efficiency. The way forward must take into account all the various aspects mentioned, whether environmental, economic, strategic or human. By promoting ‘green’ alternatives, optimising use and reclamation, we can create new resources by recycling and diversifying our sources of supply. At the same time we relieve the pressure on natural resources, we limit our dependence on exogenous markets and maintain better control of costs and operating conditions. To do this, we need real economic intelligence, as well as the ability to anticipate and invest so that we don’t jeopardise the long term by having a short-sighted view today. In short, no longer putting all our trust in market mechanisms as our sole compass, in a culture of indifference. Instead we should learn to question, try new things and not be afraid to innovate.

BIOMIMETICS How do we enthusiastically achieve sustainable innovation? When designers get a bit carried away by their work and start to change things that are familiar to us, it’s easy to feel a bit bewildered by their answers to the many questions that sustainable development can raise. Some ‘eco’ initiatives tend to sound like decline, with virtuous efforts, with restrictive methods and off-putting obligations. The very special asset of the biomimetic approach – which is one of many – lies in the fact that it tends to arouse our child-like curiosity which has sometimes been buried for a long time. Remember the fascination and excitement you experienced at discovering how something worked? The biomimetic method turns us into enthusiastic pupils again and, in the course of this renewed apprenticeship, there lies a wonderfully creative terrain, an immense reservoir of inventions awaiting our ingenuity to be deployed on a human scale, following rules dictated by nature over millennia. Rules that apply moreover to respect for the environment and the species that inhabit it, as a bonus for looking at and listening to nature. The biomimetic approach, if it is made carefully and intelligently (if and only if the method is not necessarily getting away from careful studies into the impacts of each decision), proves to be intrinsically sustainable. Everything started 3.7 billion years ago. Man’s existence represents only a fraction of a second in this huge time span. And yet man, long convinced of his superiority, has 354

endeavoured in such a short period of time, to imperil natural balances that have been finely tuned over a very long period. The appearance of life on Earth was the start of a great adventure which eventually led to the formation of the biggest research and development laboratory ever set up. Today’s biomimetics movement, for which Janine Benyus is the best-known ambassador, is obviously based on this observation. She is an American scientist who published a book, Biomimicry: Innovation inspired by Nature, in 1997. Janine Benyus invented the word ‘biomimicry’, an emerging discipline, also known as ‘biomimetics’. It’s about learning FROM nature. For some, biomimetics is a methodology for seeking and finding solutions. For others, a philosophy or a design approach. Becoming apprentices to nature, reversing our relationship with it, changing from domination to appreciation, to optimising rather than maximising, these are the keys to biomimicry. Put very simply, it may be noted that nature follows rules that would be advisable for us to adopt as quickly as possible: nature only uses one form of energy, solar energy and uses only the necessary amount; it recycles everything; it ‘knows’ how to adapt form to function; it banks on diversity and works with local expertise and resources; it limits its own excesses; adversity becomes a source of creativity. So many principles, that numerous designers, engineers, major industrial groups and communities are starting to latch onto ‘eco-designed’ projects. Certainly, the biomimetic approach can be employed without any particular ethics, but what Janine Benyus and her supporters defend is responsible practice, the main interest. By following the method with respect, projects are bound to be sustainable, ensuring that future generations have a healthy, well-adjusted and viable ‘habitat’, elegantly achieved. Our human history has to its credit great individuals like Darwin, D’Arcy Wentworth Thompson, Leonardo da Vinci, Jacques de Vaucanson or Louis Sullivan, whose research, experiences and writing show that this interaction with nature and the source of inspiration that it constitutes is absolutely nothing new. Today, biomimetics is recognised as a discipline in its own right, productive across a wide range of fields. From biomimetic materials, like the famous Velcro® developed by Georges de Mestral after his accurate observation of the way burdock burrs hooked into the hair of his dog, to biomimetic buildings like the Eastgate Centre commercial building in Zimbabwe, fully ‘air-conditioned’ without using electricity or any normal systems. This was designed by architect Mick Pearce who took his inspiration from the thermal regulation systems discovered in giant termite mounds. Aviation passed through all its well-known stages of development, after being initially inspired by observations of birds and other flying creatures. There are plenty of examples of the biomimetic method in use today. What seems very odd is that this fantastic natural source of solutions has not so far been more exploited by man. A study by Julian Vincent in the UK reveals that for a given problem, if the patents registered by people for solutions are compared with solutions already found by other living organisms in nature, the answers always differ. Proof of what lies ahead and the potential offered by this method. Sit biologists down with designers and the result is: ideas. A multidisciplinary approach to innovation, a new way of envisaging inventions and designs taking inspiration from life itself. 355

We shall soon see the day of photovoltaic systems that don’t have much in common with the solar panels that we already know. New generations in this field have been able to build on the incredibly complex functions of green plants, capable of capturing solar energy and converting it into essential energy. Photovoltaic engineering is firmly in the era of photosynthesis reinterpreted by man. The means employed are simpler, more local, less onerous but also, and above all, less harmful for the environment. While on the subject of energy, there are plenty of other examples of biomimetics such as the development of silica aerogel, an incredibly light material with an almost unequalled thermal insulating ability. Silica aerogels, or nanogels, were developed from research carried out on diatoms, fascinating marine organisms capable of fabricating silica exoskeletons at very low temperatures. Pure glass, made at the bottom of the sea. All of the ‘sol-gel’ techniques in use today for the production of thin, protective layers of glass are inspired by these living aquatic creatures. The development of such cold fabrication techniques, described as ‘cold chemistry’, is at the heart of the issues of saving energy and ecology. Still in the domain of energy and the oceans, various companies have developed units for electricity production using marine currents, one of which is inspired by the curves on the fins of certain tuna fish. Another company proposes windmills with a blade profile based on the shape of humpback whale fins. These animals have fins with an uneven edge profile, which has been found to have better hydrodynamic efficiency than a smooth edge, hence the aerodynamic adaptation for a windmill. Research on the ability of mussels to adhere to a support has resulted in the extraction of a protein which is particularly effective as an adhesive. This protein is now synthesised from soya and used in the adhesive for chipboard and plywood panels. An American company uses it to offer wood products without any formaldehyde. One of the important aspects of biomimetics is to remain careful in ensuring that people don’t profit from exploitation of living organisms. Identify a particular adhesive in mussels, that’s perfectly good, but then to profit by either cultivating a huge number of mussels with the aim of harvesting this protein, i.e. creating protein ‘factories’, or to genetically modify the mussel or any other organism to obtain this protein, is certainly not good. It’s easy to connect biomimicry and domestication, making genetic modifications for our benefit. We therefore have to be careful not to go beyond certain limits to preserve a natural equilibrium. A precarious balance that each ecosystem needs to maintain. The life of living species is based on interdependent relationships which can be the inspiration for biomimetic solutions to our problems. The Danish town of Kalundborg decided to initiate the exchange of good practices between different companies and groups, thus producing a real ecosystem on an urban scale. Water used by one company is recovered by another, which in turn offers its waste to a third entity, which itself recovers energy from a fourth and so on. By developing a complete system of exchanges and symbiotic relationships, the town reduces its water and energy consumption, optimises its waste management and promotes a spirit of cooperation. Biomimetics therefore comes in at several levels, from the question of materials and technologies to questions of strategies and organisation on a bigger scale. 356

As may be imagined, various balances remain rather delicate. Biodiversity is under threat, while its preservation makes sense for disciples of biomimicry. In fact, if we destroy this great database of natural ‘family recipes’ that each species has, how can we hope to make use of it one day? The potential knowledge possessed by all living organisms on earth should be jealously preserved and catalogued so that we may use it to survive. There is no sentimentality here, just a practical vision of the issue at stake: biodiversity must obviously be protected so that we can make full use of it. We have to expand our knowledge and we must look again, again and again into the living world around us. It’s clear that all aspects of teaching how to acquire the knowledge of ‘how things work’ become of great importance if we are to become good apprentices to that exemplary mentor, Mother Nature. In the late 15th century, Leonardo da Vinci was already urging us emphatically ‘Go, take your lessons from Nature’.

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Nano-this, nano-that Nanomaterials and nanosciences have erupted into the evolving galaxy of materials. Beyond the impressionist effect and escalation caused by the ‘need for new’ present in our societies, what is actually the issue here? When it comes to nanomaterials, it is not necessarily a question of the emergence of one or more new and previously un­known substances; it is a question of a new and particular scale on which to observe matter. This scale, the nanometre, 10 to the power minus 9-m, is one millionth of a millimetre. A nanoparticle is a dwarf-sized particle (the Greek for dwarf being nanos), the size of just a few molecules. To give an idea of this scale: an atom is 0.1 nanometres; one hair measures 50,000 nanometres in diameter! The range of experimentation conducted by scientists in this domain starts at one nanometre and goes up to a few hundred nanometres. ‘Nanoparticles’ is a term often used in this field. The aim is to understand why this totally new scale of observation for matter has become so strategic in such a short period of time. One of the general tendencies of industrial and scientific progress since the beginning of the 20th century has been towards miniaturisation, in other words, the reproduction of phenomena seen on a macroscopic scale, at reduced scales whilst still maintaining the same effects. We have reduced the size of radios, motors, domestic appliances, telephones, computers all in the name of weight loss, de-cluttering, or energy consumption (and other similar reasons), giving us a whole new, reduced-size ideal scenario. The race to reduce and to master the ever-shrinking world of technology has come up against a wall. This wall, has proven to be a nanometric one! At this scale, we see that the fundamental properties of materials are dependent on their size. When size is reduced, the volume of an object decreases proportionally, and at a faster rate than the surface area. This has very few consequences up to a certain point (this point being when the atoms of the surface begin to play a predominant role in relation to the atoms of the object’s interior). From this point onwards, we see ‘exotic’ behaviour beginning to appear, even new behaviour, linked to the quantum effects or to the wave/ corpuscle duality of atomic matter. Conductivity, melting point, and optical properties can find themselves considerably modified. The colour of gold at a nanometric scale, for example, can become red, orange, or green. These behavioural modifications which initially appeared to be obstacles to miniaturisation, have in fact turned out to have strong potential for innovation. In a minuscule space, in a nano space, everything is there to be rediscovered, everything is there to be reinvented and under a rewritten rule book. The capacity which scientists have acquired to manipulate matter on an atomby-atom basis, allows us to pursue both this business of miniaturisation, the so-called ‘descending’ pathway, and also the reverse: the ‘ascending’ pathway, which uses these previously unknown properties of nanometric matter to rebuild matter on the basis of totally new objects, to import the properties of the nano world into the macro world. This giant leap forward has been made possible by the invention of certain tools which allow us to see and manipulate matter: the local probe microscope, the STM (Scanning 358

Tunnelling Microscope), optical tweezers, the synchrotron,etc. An increasingly fine mastery of the lithography procedures, associated with short-wavelength laser beams or X-ray or electrons beams, allows us to observe, to manipulate and to guide the assembly of nanomatter. It is these tools which have guided the most spectacular inroads into electronics and information technology. Most notable have been the advances in microprocessors, which have attained sizes of just a few dozen to a few hundred nanometres. Making and reproducing nanometric objects and systems on a large scale is now becoming one of the conditions of progress for these materials. In this domain, the so-called ascending pathway has proved to be very promising. It involves taking atoms or molecules – under closely controlled conditions – which, forming a veritable ‘seed’, then spontaneously self-organise and form ‘supracrystals’ whose structure determines the new electrical, magnetic, and optical properties of the material. Being able to store information in these structures would increase the amount of information on a current hard drive by about 200 fold. As our understanding of nanotechnology deepens, an armoury of applications seems to be emerging in numerous technological domains linked to electronics and chemistry. We find nanotechnology in medicine: in diagnostics, medications, and carbon nanotubes (used as supports for molecules in prosthetics and bio-compatible implants). We also find it in metallurgy where it is used to improve the performance of alloys (nano-structured copper is three times stronger than ordinary copper). We find them in reinforcements for composite materials, in the development of hybrids, in gels, cosmetic foams, in the perfecting of material wettability, in water-repellence for glass (self-cleaning glass). More generally, nanotechnology is used in the guise of ultra-thin coatings and coverings, for protection, decoration, or optical effects. We find nanotechnology in the adhesives industry (gecko effect), in the domain of filtration (nanogels) and in the spectacular manu­facture of nano-motors (actual tiny vehicles capable of modifying, reorganising, and transporting substances on a molecular scale to the surface of certain materials). We find nanotechnology in the domain of light, with the appearance of photonic crystals, which may lead to the production of highluminosity, low-energy super LEDs. It follows logically that a large number of industrial production sectors are turning toward nanotechnologies, calling upon large portions of their Research & Development budgets. The USA, China, Asia, and Europe all foresee impressive growth in this area. However, these predictions of rapid growth do lead to serious worries over the risks incurred by mass production of nanoparticles. Numerous studies are underway to evaluate the degree of toxicity of metallic oxide nanoparticles and carbon nanotubes, substances which find it particularly easy to cross the mucous membranes and the cutaneous barrier, accumulating in cells. The mastery and control of this large-scale proliferation of nanoparticles is not yet commonplace. Indeed, the tragic experience of asbestos industrialisation prompts the scientific and technical community to be especially cautious. On the other hand, it is easy to picture the positive role which nanotechnologies may play in the miniaturisation and generalisation of RFIDs (radio frequency identification device), in stock management, food traceability, and urgent medical attention. Just as easy to imagine are the slippery slopes which such systems may cause our societies to embark on in terms of control, surveillance, protection of 359

civil liberties, or of confidentiality. Human beings controlled in real time: but for whose sake and to what ends? Science only lends further questions by way of answer to these already thorny issues: rendering a political and social debate, which must be inherently wider than the inner sanctums of scientific experts, all the more urgent.

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De natura materiae One might expect a reference work dedicated to materials to have a rigorous and concise definition of its subject. Though we succumbed to the temptation of defining matter, we very quickly latched onto all the vanity of the task it sets out to achieve and noted that seemingly ordinary statements, immediately become entangled in an endless stream of unanswered questions. Matter, which seems so familiar at first glance, so immediate and so real, seems to slip through our fingers every time we approach a good definition. One of the main difficulties in understanding the concept of matter, is that it requires many tools which do not all employ the same level of language and approach. Matter can be experienced through sensory perception, technical description, scientific theory, or a philosophical approach – so many possibilities which inextricably overlap elements of different definitions. That which we believe to be this intangible reality that sometimes seems to BE matter, never in fact existed ‘materially’, in the common sense of the word. A troubling statement which Schrödinger, one of the radical pioneers of quantum phys­ ics, introduced when he said ‘abandoning trajectory is tantamount to abandoning particles and what is more, these particles, did not even exist in our naive understandings of yesteryear’. But since we must call a spade a spade (or a cat a cat in Schrödinger’s case) it is our spontaneous and immediate perception, our senses, which we often come to rely on. This way of grasping, by sensory experience, that which we believe to be reality, does provide us with a first level of efficiency, but it is unfortunately (or fortunately, perhaps) very far from the end of the matter. In fact our senses are quite limited in their role as measuring instruments; animals have other methods of measurement and perception. Thought, on the other hand, is capable of interpreting reality in other ways. There is, therefore, a cohabitation which surrounds us. A duality of things which are almost material, and others which are almost immaterial. If we go by the principle that matter and thought are part of reality, the difference between these two states is distinct and real. Obviously, the distinction is less clear-cut when our perception of the material world is gained via the intermediary of an immaterial experience such as thought (as offered by mathematicians). And it is at this crossroads that the concept of matter, appearing so stable, suddenly finds the ground taken out from under its feet. To each and every society since ancient times, pinning down a definition of matter has always seemed a necessary and unquestionable pursuit; if only to give us an idea of how to act and react to the strains and constraints of what is commonly called Nature. The multiple attempts to penetrate the inner secrets of matter have by no means developed in a totally linear fashion: theory upon theory has been disproved by veritable revolutions, and huge names are inextricably linked with this process: Plato, Aristotle, Galileo, Newton, Descartes, Einstein, and Heisenberg, to name but a few. The oldest traces of these questions are found in 5th century Greece; Leucippus and Democritus describe matter as a multitude of grains, solid bodies, which are hard and indivisible – from which atoms get their names – unique in nature but unlimited in number, and sometimes bumping into each other to form aggregates. This rather rudimentary idea of the ‘atom’ gave birth 361

to a debate between Plato and Aristotle, regarding the inseparable coupling of form and matter. According to Plato, if matter is considered as an invariable, an undetermined substrate, almost invisible and only seen through form, then form, conversely, is a chang­ing reality, divisible, and reconstructable. Plato distinguished matter as being: ‘that which is always becoming, that which something becomes, and an appearance which gives birth to that which becomes’. To counter this proposal, Aristotle suggests there is a subjacent entity to form, into which an essence is vested; in modern-day terms, one might say that it had ‘information’ contained within it and was capable of acting upon this. Aristotle unites form and matter in an irreducible way. It is from this very debate that the Middle Ages inherited the curiosity which drove them to move away from the idea of the atom and impose that of a shapeless matter-come-substance, given by God: materia prima, and uphold that it would not be wise to question its nature. However, it is precisely this task which alchemists undertook. Sometimes in hiding they developed a strong mysticism around matter, sometimes pagan-based, which opposed the idea that only God can fundamentally transform matter. Some saw in alchemy, this hazy met­aphysics, an embryonic state of what would become modern chemistry. But science had to wait until the Renaissance before it could unhitch matter from the shackles of religious interpretation and associate the concept of matter with the idea of movement. Galileo, apart from his famous heliocentric definition of the heavens, also gave a definition of matter: ‘That which remains ‘in its being’ during movement’. From the 17th century the conception of matter became one, no longer of substance, but of material particles and indivisable atoms, which move about in an empty space. Isaac Newton bestowed upon these particles a new property: that of mass, which supplemented that of movement. Descartes contributed to this definition by operating a stark distinction between material substance and spiritual substance, imposing the idea of a world where God gives instinctive impulsion which gives mechanical matter its mechanical autonomy – the inexorable ability to move by contact and friction. The introduction of mechanics which was free from all metaphysical interpretations, gave rise to a spectac­ ular development during the 19th century. Physics and chemistry became the principle decision-makers in the definition of matter from this point onwards. One of the questions confronting those who wish to define matter is often summarised as an analogy to bricks or the alphabet. Is the atom an inert element, piled up like bricks, to make matter which is likened to a building or is it the active element which alters itself to create a matter which is more like ‘language’? Lavoisier, Dalton etc all bring us closer to a definition of matter as an assembly of atoms, limited in number, which Russian chemist Mendeleyev arranged into his infamous periodic table in 1869. During the 19th century, the structure of matter became atomic once again − the physics and chemistry of the atom began to converge − showing a clear vision of matter and opposing metaphysical interpretations. To think of matter in mechanical, atomic terms, far from being a simple intellectual exercise, has only proved possible over more than two centuries of progress, which a purely empirical approach would probably not have achieved. The industrial revolution placed matter at the heart of our societies, but the story seemed done and dusted when the atom made up the solid basis of the terrible events of Hiroshima in 1945. Einstein 362

introduced relativity and the destabilising idea that light − which was considered up until then as a wave phenomenon − could also be corpuscular in origin. Photons: neither wave nor matter particles, but in fact both. Quantum physics was quick to jump aboard with the idea of photons and replaced notions of mass and movement with those of energy, fields, and quanta. Quantons, new physical beings, oppose the idea of atoms being solid objects and overturned the understanding of matter as an impermeable object occupying a portion of space and possessing mass. Undeniably, quantum phys­ics has opened a new era of matter interpretation. On the other hand, the advent of new physical objects such as antimatter, black holes, chaos theory and phenomena, as well as fuzzy logic all testify to the fact that the classic mechanical and atomic conception of matter, put forward by the Renaissance era, is behind us. The phenomena of an information society and the concept of dematerialisation which accompanies this trend seem to dominate the horizon at the moment. Does this dematerialisation indicate that the era of matter will come to an end and cede its place to an era of virtuality? It is actually probably the opposite which is in danger of occurring at the moment, because now, although world consumption of primary raw materials has dropped spectacularly, the production of consumer objects and goods is increasing just as fast. The notion of service often goes hand in hand with one of an increase in energy usage, in other words, matter usage. In fact the question does not hinge on the disappearance of matter, but on new productivity and the new forms under which it will reappear and be manipulated. In this vein, Aristotle’s argument of matter and its form is very likely to regain vigour and the new, exotic approach of quantum physics may also powerfully overturn our way of life and reintroduce questions as to the essential nature of matter. Upheavals like this do not lack the impetus to be the driving force behind the kind of questions which matter has always raised: it is our central object of concern, of fascination, in so much as we are made of it and yet the dream of understanding it always appears like a mirage the closer we get to it.

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Index A Abrasion p.128 / 141 / 142 / 150 / 164 / 1 86 / 217 / 221 / 225 / 261 / 262 / 263 / 269 / 270  / 283 / 327

Acrylic p.157 / 173 / 194 / 216 / 236 / 279 / 2 81 / 309 / 326

Acrylonitrile Butadiene Styrene (ABS) p.68 / 69 / 119 Additive p.27/55 / 68 / 69 / 100 / 128 / 137 / 140 /  141 / 151 / 178 / 195 / 207 / 219 / 225 / 325 / 326

Aramide p.68 / 152

Bituminous concrete p.100

Carbon dioxide p.133

Architectonic concrete p.140

Blade p.149 / 243 / 261 / 262 / 263 / 356

Carbon monoxide p.132

Artificial p.65 / 131 / 135 / 151 / 157 / 159 / 16

Blank holder p.291 / 315

Cardboard p.21 / 25-32 / 133 / 170 / 257 / 

9 / 176 / 189 / 223 / 303 / 341 / 346

Blank p.265 / 291

263 / 265 / 266 / 281 / 283 / 289 / 291 / 303 / 321 / 

Ash p.245 / 266

Blanket p.321 / 323 / 327

326 / 327 / 349

Asphalt p.123

Blast furnace p.42 / 44 / 45 / 134

Carded sliver p.82

Assembly

Bleaching p.27 / 86

Carding p.82 / 86

p.126 / 133 / 170 / 174 / 175 / 195 / 272-

Bloom

Cast iron p.42 / 44 / 45 / 46 / 47 / 134 / 23

277 / 279 / 283 / 285 / 289 / 296 / 321 / 359 / 362

Blowhole p.293

8 / 293 / 326

Atom p.41 / 42 / 66 / 108 / 132 / 145 / 230 / 337 / 

Bluebottle effect p.325

Cast iron, grey p.134

356 / 358 / 359 / 361 / 362 / 363

Bombyx p.154

Cast iron, spheroidal graphite

Awl p.289

Bonded-fibre fabrics p.86

p.134

Bonding p.273 / 278-

Cast iron, white p.134

279 / 282 / 285 / 313 / 318 / 325 / 327

Casting, lost wax p.293

Bonding primer

Casting, sand p.293

Adhesion p.191 / 220 / 236 / 279 / 283 / 298 Aerogel p.58 / 102 / 120 / 357 Agro-composite p.127 Air mould p.306

B

p.45

p.282

Borosilicate glass p.55 / 163 / 167

Catalyst p.58 / 149 / 212 / 279 / 299 / 325

Albumin p.62 / 144 / 282

Bakelite (PF) p.125

Brass p.44 / 46 / 47 / 129 / 130 / 143 / 253 / 

Cathode p.46 / 180 / 326 / 327 / 329

Alcantara p.198

Ballast p.140 / 141 / 169 / 181 / 183 / 185 / 195

295 / 305

Cedar p.13 / 248

Alchimiste p.65 / 91 / 178 / 339 / 372 Alloy p.44 / 47 / 68 / 122 / 129 / 130 / 143 / 

Balsa p.250

Brick p.60 / 61 / 62 / 138 / 162 / 192 / 195 / 

Cellular concrete p.140

Bamboo p.25 / 26 / 28 / 88 / 126 / 156 / 173

309 / 362

Cellular p.78 / 140 / 158 / 170

168 / 178 / 186 / 187 / 188 / 192 / 230 / 235 / 237 / 

Bark

Brining / Pickling

238 / 239 / 241 / 242 / 252 / 253 / 263 / 265 / 283 / 

Basalt p.82 / 92 / 124 / 152

Broad-leaved tree p.11 / 14 / 16 / 26 / 

p.135 / 151 / 232

285 / 293 / 295 / 297 / 299 / 305 / 309 / 310 / 359

Base p.15 / 16 / 131

246 / 247 / 248 / 249 / 250

Cellulose p.16 / 25 / 26 / 82 / 127 / 128 / 135 / 

Alucobond® p.121

Batch mixing p.100

Bronze p.41 / 44 / 46 / 47 / 130 / 241 / 253 / 29

151 / 155 / 232 / 282 / 326

Aluminium (Al) p.41 / 42 / 44 / 46 / 47 / 

Bauxite p.42 / 122 / 161

3 / 297 / 318 / 339

Cement concrete p.100 / 140

50 / 76 / 120 / 121 / 122 / 129 / 137 / 140 / 143 / 

Beech p.208 / 245 / 248 / 266

Buckling p.86

Cement p.78 / 99 / 100 / 101 / 102 / 140 / 141 / 

158 / 161 / 183 / 170 / 188 / 194 / 226 / 235 / 236 / 

Bending p.19 / 258 / 267-267

Buckskin p.36 / 198

142 / 195 / 201 / 227 / 283 / 351

242 / 252 / 265 / 293 / 295 / 297 / 310 / 313 / 315 / 

Bendyply®

Bulk Molding Compound

Centrifuging p.258 / 313

318 / 327 / 331 / 339 / 348 / 349 / 350

Bendywood®

(BMC)

Ceramic tiles p.136

Amalgam p.192

Beryl p.148

Bulking paper p.25 / 27 / 28 / 200

Ceramics p.53 / 60-62 / 75 / 76 / 137 / 138 / 

Aminoplast p.281 / 282

Bi-injection moulding p.308

Burr p.16 / 131

187 / 206 / 227 / 230 / 233 / 283 / 297 / 299 / 303 / 

Amorphous p.41 / 50 / 54 / 55 / 60 / 66 / 

Billet p.45 / 310

Butt p.35 / 36

67 / 68 / 119 / 120 / 135 / 145 / 149 / 186 / 205 / 

Binder p.100 / 150 / 172 / 191 / 195 / 200 / 

Ceramics, architectural p.138

210 / 212 / 216 / 219 / 222 / 251 / 328

201 / 282 / 297 / 325 / 326

Ceramics, technical p.62 / 137

Anaerobic p.127 / 279

Bio-ceramic

Anamorphosis p.328

Biodegradable

Angiosperm p.14

133 / 350

Calcium p.132 / 172 / 196

Chamotte p.60

Angora p.154

Biofragmentable p.128

Calcium carbonate p.185 / 190 / 196

Cherry tree p.247

Anisotropy p.11 / 16 / 44 / 295

Bioluminescence p.108

Calendering p.27 / 258 / 302-303 / 310 / 

Chestnut p.12 / 248

Annealing p.46 / 56

Biomass p.127

325 / 327

Chipboard p.70 / 139 / 175 / 191 / 199 / 

Annual growth ring p.15 / 16

Biomimetics p.354 / 355 / 356

Cambium p.15 / 16

283 / 356

Anode p.46 / 190 / 326 / 327 / 329

Biomineral p.354 / 355 / 356 / 357

Cambium p.15 / 16

Chroming p.252 / 341

Anodisation p.46 / 122 / 327

Biopolymers

Carat

Chromium p.44 / 46 / 47 / 148 / 228 / 237 / 347

Antimony p.47

Bio-sourced p.127 / 350

Carbohydrate p.146

Anvil p.295

Birch p.12 / 131 / 208

Carbon nanotubes p.132

150 / 185 / 187 / 195 / 227 / 228

Aragonite p.196

Biscuit / Bisque p.62 / 136 / 315

Carbon p.42 / 44 / 65 / 66 / 68 / 74 / 76 / 77 / 

Cleavage p.94

Araldite® p.149

Bitumen p.100 / 123

120 / 132 / 134 / 146 / 149

Co-extrusion p.309

p.15 / 16 / 88 / 144 / 156

p.209 p.209

p.62

p.34

p.78 / 212 / 301

C

305 / 309 / 326 / 328 / 350

Ceramics, traditional p.138 Chalk p.92 / 185 / 202 / 225 / 325

p.70 / 127 / 128 / 

p.11 / 70 / 88 / 127 / 128 / 156

Cellulose acetate (CA)

p.146 / 148 / 168 / 223

Clay p.60 / 91 / 92 / 94 / 100 / 293 / 297 / 136 / 138 / 

367

F

Co-injection moulding p.308

Covalent link p.66

Drop forging p.205

CO2 p.14 / 127 / 351

Covering p.129 / 306

Drum p.36

Coal p.42 / 44 / 66

Crack p.18

Ductility p.44

Coating p.27 / 88 / 102 / 123 / 125 / 129 / 

Crimping p.266

Dyeing p.36 / 86

149 / 173 / 184 / 185 / 189 / 200 / 207 / 213 / 214 / 

Cross-grained wood p.16

220 / 222 / 253 / 283 / 292 / 303 / 325 / 326 / 

Crown p.15

327 / 341 / 359

Crystal lattice p.42 / 44

Cobalt p.44 / 47 / 297

Crystal p.42 / 55 / 132 / 145 / 148 / 167 / 

Codex p.26 / 202

176 / 179 / 180 / 206 / 219 / 223 / 226 / 251 / 

Earth’s crust p.92 / 169 / 224

78 / 82 / 86 / 88 / 104 / 107 / 109 / 112 / 126 / 131 / 

Coke p.44 / 45 / 134

342 / 350 / 359

Earthenware p.60 / 62 / 136 / 138 / 326

135 / 137 / 141 / 149 / 150 / 151-157 / 193 / 201 / 

Collagen p.34

Crystalline p.42 / 43 / 44 / 50 / 54 / 60 / 66 /

Ebony p.12 / 250 / 339

210 / 212 / 213 / 215 / 216 / 244 / 250 / 252 / 295 / 

Colorant p.27 / 68 / 86 / 325 / 327

 67 / 68 / 92 / 94 / 145 / 169 / 178 / 204 / 210 / 213 / 

Eco-label p.348 / 349

299 / 301 / 305 / 306 / 313 / 326 / 349 / 350 / 351

Colour Rendering Index (CRI)

214 / 217 / 218 / 220 / 229 / 251

Ecology p.88 / 199 / 205 / 222 / 326 / 345 / 

p.108

Crystallite p.42 / 43

347 / 350 / 356

Colour temperature p.108 / 109

Cullet p.56

Edge trimming p.261 / 263

Company-declared information

Cupro-aluminium p.44 / 143

Elastane p.88

p.348

Cupro-cellulose p.151

Elasticity p.42 / 68 / 100

Composite p.11 / 16 / 70 / 73-80 / 81 / 121 / 

Cupro-nickel p.44

Elastomer p.68 / 221 / 225 / 234 / 240 / 

125 / 126 / 127 / 137 / 141 / 152 / 153 / 170 / 193 / 

Curling p.18 / 19

262 / 305 / 321

208 / 212 / 213 / 228 / 229 / 244 / 250 / 257 / 283 / 

Cutting

Electric Discharge Machine

301 / 313 / 315 / 350 / 359

153 / 162 / 171 / 176 / 209 / 223 / 236 / 243 / 257 / 

(EDM) p.270

Compostable p.128

260-263 / 269 / 273 / 309 / 310 / 315 / 319

Electricity p.108 / 112

Conchyolin p.196

Cyanocrylate p.70 / 279

Electrochromic p.251

p.15 / 16 / 17 / 18 / 121 / 131 / 146 / 

Fabric p.82 / 84 / 86 / 87 / 160 / 162 / 166 /  212 / 218 / 261 / 289 / 322

Feed hopper p.304 / 309

E

Feldspar p.60 / 61 / 136 / 169 / 228 Felt p.27 / 86 / 154 / 198 / 318 / 150

Fibre, artificial p.82 / 151 / 157 Fibre, carbon p.68 / 74 / 104 / 152 / 212 /  213 / 301

Fibre, glass p.68 / 74 / 77 / 76 / 141 / 152 /  153 / 193 / 210 / 213 / 301

Fibre, mineral p.82 Fibre, optical p.53 / 107 / 109 / 112 / 142 / 

141 / 142 / 153 / 169 / 174  / 185 / 191 / 222 / 233 / 

Electro-zincing p.46

Concrete, glass reinforced

Fibre, aramid p.152

Fibre, man-made p.82

Electro-rheological p.197

D

Fibre, animal origin p.82 / 151 / 154

Fibre, basalt p.152

Concrete p.78 / 96 / 99-106 / 123 / 140 /  257 /  262 / 263 / 269 / 281 / 299 / 351

Fibre p.16 / 26 / 27 / 34 / 53 / 68 / 74 / 76 / 77 / 

153 / 216

Fibre, synthetic p.82 / 151 / 157

Electrode p.146 / 147 / 180 / 270 / 284 / 285

Fibre, vegetable origin p.82 / 155-156

Electroluminescence (EL)

Filament p.82 / 83 / 107

(GRC) p.153

Dacron® p.157 / 215

p.30 / 107 / 109 / 147 / 180

Concretes, conventional

Deactivation p.102

Electrolysis p.241 / 253 / 305 / 326 / 327

p.140 / 142

Dehairing-lime treatment p.36

Electromagnet p.189 / 193 / 239

Concretes, fibre p.141

Deliming p.36

Electron p.42 / 66 / 176 / 204 / 205 / 217 / 

Concretes, high performance

Dematerialisation p.363

229 / 326 / 329 / 359

p.142

Denier p.84

Electroplating p.327

Coniferous trees p.11 / 14 / 16 / 26

Density p.55 / 73

Embossed stone p.94

324-329 / 341 / 351

Contouring / fretwork p.261 / 262

Dentine p.172

Emerald p.92 / 148 / 223

Fir p.13 / 246

Cooling block p.266 / 309

Dermis p.34 / 35 / 36

Enamel p.4 / 60 / 62 / 124 / 136 / 138 / 164 / 

Fire-proofing p.18 / 20 / 68 / 88

Copier p.270

Diamond p132 / 146 / 223 / 229 / 261 / 

227 / 326

Flame cutting p.261 / 262

Copolymer p.68

262 / 263 / 270

End-grained wood p.15 / 16

Flaming p.94

Copper (Cu) p.42 / 44 / 46 / 47 / 121 / 122 / 

Diamond point p.261 / 262 / 263

Endmill p.269

Flank p.35

129 / 130 / 143 / 151 / 158 / 168 / 194 / 204 / 229 / 

Die punch p.263 / 265 / 269 / 327

Energy p.14 / 107 / 112 / 120 / 122 / 164 / 

Flat-grained wood p.15 / 16

230 / 235 / 239 / 241 / 245 / 252 / 265 / 309 / 321 / 

Die-stamping p.303

180 / 187 / 203 / 204 / 205 / 206 / 224 / 229 / 239 / 

Fleece p.37 / 154 / 331

353 / 359

Digital processes p.316-317

262 / 285 / 295 / 332 / 345 / 347 / 348 / 350 / 351 / 

Flesh p.4 / 35 / 159 / 198 / 202 / 231 / 340

Corian® p.236

Dilatant p.197

352 / 355 / 356 / 358 / 359 / 363

Flexible wood p.22 / 209

Cork p.144 / 195 / 283

Dip transfer p.328

Engineered Wood Products

Flexographic printing p.321

Corn p.70 / 88

Discharge p.109 / 110 / 181 / 183 / 184 / 270

(EWP) p.20

Float glass p.56 / 57 / 58 / 164

Corrosion p.46 / 50 / 122 /  130 / 134 / 137 / 

Dowel p.272 / 275

Epidermis p.34 / 35 / 36

Flocking p.327

143 / 149 / 152 / 164 / 168 / 178 / 188 / 194 / 195 / 

Draft angle p.291 / 293 / 295 / 299 / 301 / 

Epoxy / Epoxides (EP) p.66 / 69 / 

Flowers of zinc p.253

235 / 237 / 238 / 241 / 242 / 252 / 253 / 327

305 / 315

70 / 76 / 149 / 152 / 173 / 195 / 219 / 234 / 279 / 

Fluorescence p.81 / 183 / 203 / 224 /  325 / 351

Corundum

Dralon®

281 / 282 / 301 / 317 / 326

Flute p.133

p.148 / 226 / 262 / 270

p.157

Filament winding p.77 / 78 / 212 / 213 /  258 / 313

Filler p.68 / 69 / 96 / 137 / 156 / 195 / 201 / 207 /  212 / 236 / 284 / 285

Finishes p.120 / 122 / 138 / 142 / 159 /  175 / 184 / 191 / 236 / 244 / 249 / 269 / 291 / 299 / 

Cotton p.25 / 26 / 82 / 84 / 86 / 88 / 135 / 151 /

Drawing p.57 / 168 / 200 / 258 / 291 / 303 / 

Extra-low Voltage (ELV) p.112 / 182

Flux p.54

 155 / 160 / 351

321 / 344

Extrusion p.62 / 74 / 82 / 119 / 151 / 152 / 

Foam p.1 / 22 / 30 / 41 / 50 / 68 / 78 / 158 / 

Cotton, ‘Egyptian’ p.155

Dressed stone p.94 / 95

157 / 170 / 215 / 244 / 257 / 258 / 265 / 302-303 / 

214 / 219 / 221 / 261 / 309 / 340 / 342 / 359

Cotton, ‘Indian’ p.155

Dressing-finishing p.36

306 / 309 / 310

Fold p.257 / 258 / 265 / 266 / 291 / 327

Cotton, ‘upland’ p.155

Drill bit p.268 / 269

Extrusion, blow-moulding p.306 / 308

Font p.321

Cotton, biological

Drilling

Extrusion, blown film

Forest p.14

368

p.155

p.121 / 218 / 244 / 268 / 269 / 310

p.309

Forest Stewardship Council

Glass, toughened p.59 / 166 / 262

FSC p.48 / 349 / 350

Glass, vitroceramic p.55 / 167

Forging p.257 / 258 / 294-295

Glaze p.165 / 200 / 201 / 328

Forging, free p.295

Glue p.26 / 70 / 139 / 170 / 174 / 177 / 202 /

Formaldehyde p.125 / 356

 221 / 245 / 249 / 273 / 279 / 280 / 281 / 282 / 283 / 

Format (paper) p.28 / 29

285 / 289 / 318 / 326 / 327

Forming p.257 / 256 / 266 / 270 / 291 / 

Glued laminated timber p.174 / 177

293 / 306 / 309 / 315

Gneisse p.169 Gold (Au) p.42 / 44 / 46 / 47 / 129 / 168 / 

Founding p.99 / 129 / 257 / 258 / 

178 / 192 / 235 / 286 / 326 / 327 / 339 / 352 / 358

292-293 / 317

Gold panning p.192 Gore-Tex® p.88

Frost susceptibility p.94 / 96

Grading p.100 / 102

Fullerene p.132

Grain p.28 / 42 / 43 / 107

Fungicidal p.18 / 27 / 68 / 326

Grain side p.34 / 35 / 36 / 174 / 198 / 20

Fur p.33 / 37 / 38 / 160

8 / 209 / 295

Fused Material deposition

Grammage p.28 / 133 / 200 / 201

(FMD) p.317 / 319

Granite p.92 / 169 / 236 p.42

Graphite p.132 / 134 / 148 / 297 Gravure printing p.321 Greenhouse effect p.14 / 55 / 345

Galena

p.178

Gallium

p.114 / 161 / 229 / 233

Greenwashing p.347 Grinder p.262 / 269

Galvanisation p.46 / 327

Groove

Gap p.123 / 229 / 297

Guillotine p.243 / 261 / 262 / 263

Gauge p.300 Gem

Gymnosperm p.14

p.92 / 145 / 148 / 223

Germanium Gimping

p.191 / 269 / 270 / 272 / 303

Gutenberg p.26 / 321

Gel coat p.280 / 281

Gypsum p.92 / 207

p.181 / 208 / 229

p.82

Glass former p.55 Glass p.0 / 54 / 53-64 / 76 / 82 / 120 / 141 / 

Lacquer p.21 / 122 / 173 / 238

Imprint

Laitance p.102

p.164 / 234 / 292

H

Lamellar p.94 / 228

p.305 / 325

Incandescence p.07 / 109 / 110 /179 / 

Laminate p.70 / 76 / 128 / 131 / 139 / 165 / 

181 / 182 / 183 / 184 / 351

170 / 175 / 177 / 191/ 194 / 196 / 228 / 241 / 249 / 

Industrial revolution p.41 / 273 / 340 / 

263 / 283

341 / 343 / 351 / 362

Laminated Object

Infrared p.55 / 88 / 108 / 109

Manufacturing (LOM) p.317 Lanthanide p.189 / 224

p.168

Injection blow-moulding

Graphene p.132 / 148

Galalith p.171

Imitation p.65

Ingot

Fresh-split leather p.36 / 159 / 198

G

L

In-mould

Formwork p.102 / 103

Granular structure

I

p.211 / 

Larch p.13 / 248

306 / 310

Laser p.8 / 107 / 108 / 176 / 202 / 226 / 

Injection moulding p.18 / 20 / 

229 / 261 / 262 / 263 / 286 / 297 / 317 / 318 / 319 / 

30 / 76 / 78 / 210 / 212 / 213 / 214 / 215 / 

322 / 359

216 / 218 / 220 / 222 / 244 / 257 / 258 / 270 / 

Latex p.16 / 68 / 127 / 158 / 173 / 225

304-307 / 327

Lathboard p.76 / 177

Ink jet p.180 / 318 / 322

Lava p.92 / 124

Ink p.30 / 147 / 150 / 235 / 251 / 320 / 321 / 

Lead (Pb) p.47 / 55 / 129 / 130 / 145 / 178 / 

322 / 323 / 327 / 328

239 / 321 / 327 / 347 / 350

Insert p.292 / 293 / 305 / 313

Lead-poisoning p.178

Invisibility p.181 / 193 / 203 / 232 / 236 / 

Leather goods p.231 / 289

262 / 362

Leather p.33-40 / 150 / 159 / 173 / 198 /

Ion p.42 / 43 / 187 / 206 / 275 / 353

 222 / 231 / 257 / 263 / 281 / 289 / 291 / 303 / 326 / 

Iroko p.250

27 / 339 / 341 / 350

Iron p.41 / 42 / 44 / 47 / 129 / 130 / 134 / 

Leather, ‘corrected-grain’ p.159

143 / 148 / 168 / 173 / 188 / 189 / 189 / 192 / 

Leather, ‘reconstituted’ p.37

196 / 220 / 228 / 237 / 238 / 252 / 265 / 285 / 

Leather, antiqued p.159

293 / 297 / 326 

Leather, full grain p.36 / 159

ISO p.27 / 28 / 201 / 348 / 349

Leather, immersion-dyed p.159

Isotropy p.44 / 55 / 191 / 297

Leather, ooze or hazed p.159

Ivoiry, fossil p.172

Leather, rough tanned p.36

Ivoiry, vegetal p.172

Leather, synthetic p.37

Ivory p.172 / 232

Leather, vegetable p.38

145 / 148 / 149 / 152 / 153 / 158 / 181 / 182 / 183 / 

Halogen p.107 / 109 / 110 / 182 / 184

184 / 185 / 186 / 187 / 178 / 181 / 182 / 184 / 186 / 

Hand p.25 / 28 / 200

187 / 194 / 204 / 212 / 213 / 223 / 224 / 233 / 241 / 

Heat sealing

257 / 258 / 262 / 263 / 265 / 269 / 270 / 273 / 279 / 

Hematite

281 / 283 / 285 / 297 / 299 / 301 / 303 / 309 / 310 / 

Hemicellulose

315 / 322 / 326 / 327 / 331 / 350 / 356 / 359

Hemp p.26 / 28 / 78 / 82 / 155 / 158 / 201 / 244

Jacquard card p.84 / 85

Life-cycle p.349

Glass, 3D p.162

Hevea p.68 / 225

Jacquard p.84

Light p.107-112 / 120 / 147 / 153 / 164 / 170 / 

High-yield-point steel (HYP)

Jersey knit

p.84

176 / 179 / 180 / 181 / 182 / 183 / 184 / 188 / 189 / 

Glass, blown p.162 / 163

p.50

Joint plane

p.295 / 305

193 / 194 / 196 / 203 / 204 / 205 / 218 / 226 / 229 / 

Glass, blowtorch

Honeycomb

Glass, armoured p.59

Glass, drawn

p.162

p.56 / 57 / 58

Leatherwork p.232

p.88 / 284-287

p.42

LED see Light Emitting Diode

J

Leuco dyes p.251 Levitation p.239

p.16

p.76 / 77 / 96 / 138 / 170 / 

Jute p.26 / 207

251 / 262 / 279 / 297 / 325 / 344 / 350 / 351 / 359

Light spectrum p.109

211 / 221 / 283

Light-Emitting Diode (LED)

Glass, enamelled p.164

Horn p.171

Glass, float p.58 / 164 / 241 / 258

Hot marking p.327

Glass, laminated p.59 / 76 / 165

Hot wire p.261 / 262

Glass, layered p.165

Hot-melt p.280 / 282

Kaolin p.60 / 61 / 136 / 325

Lignin p.16 / 191

Glass, metallic p.50 / 54 / 186

Hydro forming p.291

Kelvin p.108

Limestone p.60 / 66 / 92 / 100 / 132 / 185 / 190

Glass, moulded

Hydrocarbon

Keratin

Limewood p.54 / 55 / 247

Glass, printed

p.162

p.164

Glass, rounded

p.162

p.123 / 132 / 211 / 217 / 

221 / 228 / 352

Hyperchoice

p.65 / 337 / 338

K

p.88 / 107 / 108 / 109 / 112 / 165 / 179 / 180 / 229 /  351 / 359

p.34 / 154 / 171 / 232

Kevlar®

p.74 / 152 / 301

Knitting

p.84 / 86 / 87 / 88

Limewood p.54 / 55 / 156 / 176 / 191 / 318 Linen p.25 / 26 / 82 / 84 / 156 / 289

Glass, security p.165

Hydrochromic p.251

Knot p.18 / 19 / 191 / 288

Liquid crystals p.58 / 70 / 251 / 342

Glass, thermoformed p.162 / 315

Hypodermis p.34

Kraft p.26 / 76 / 133 / 175 / 201

Liquidmetal® p.54 / 186

369

Lithium p.187 / 352

Mitre joint p.261

Lithosphere p.92

Möbius band p.331 / 348 / 349

Log p.14 / 15 / 16 / 249

Mohair p.154

Lotus p.88

Mohs p.94 / 146 / 148 / 223 / 226

Low voltage (LV) p.179 / 182 / 285

Molasse p.227

Lumens p.108

Molybdenum p.44 / 47 / 237 / 238 / 242

Luminophore

Monomer

p.180

p.66 / 67

Luminous efficiency p.108 / 109

Mortar p.96 / 100 / 124 / 195

Luminous flux p.108

Mortar, lime p.195

Luxury p.33 / 131 / 196 / 231 / 289 / 327 / 339

Mortise p.270

Oak p.12 / 246 Obsidian p.56 / 223 Offset p.200 / 201 / 321 / 323 Okoume p.208 / 249 Onyx p.223 Opal p.223 Ore p.42 / 45 / 91 / 161 / 192 / 253

Mould p.02 / 124 / 125 / 130 / 133 / 182 / 209 /  234 / 247 / 252 / 270 / 290 / 292 / 293 / 298 / 299 / 

M

O

300 / 301 / 304 / 305 / 306 / 307 / 308 / 310 / 312 /  313 / 314 / 315 / 316 / 325 / 327

Machining p.29 / 134 / 143 / 146 / 162 / 

Moulded cardboard p.133

178 / 191 / 216 / 257 / 258 / 268-271 / 293 / 309

Moulded plywood p.209

Macromolecule p.66

Moulding p.124 / 125 / 129 / 130 / 133 / 

Magma p.92 / 93 / 124 / 169

Organic Light Emitting Diode (OLED) p.112 / 179 / 180 / 229 Oriented Strand Board (OSB) p.11 / 199

Origami p.25 / 201 / 265 / 201 Orthogneiss p.169

Phosphorescent Organic Light-emitting Diodes (PHOLED) p.180 Photochromic p.58 / 251 / 342 Photovoltaic cell p.204 / 205 / 229 / 356 Photon p.107 / 176 / 204 / 363 Piezoelectric p.60 / 62 / 206 Pigment p.27 / 68 / 102 / 132 / 164 / 168 / 178 /  189 / 195 / 242 / 251 / 325 / 342

Pine p.13 / 199 / 245 / 249 Plain weave p.75 / 84 / 85 Planing p.270 Plasma p.88 / 108 / 179 Plaster p.78 / 195 / 207 / 299 Plastic p.16 / 65-72 / 75 / 110 / 122 / 125 /  127 / 130 / 135 / 143 / 144 / 152 / 158 / 165 / 166 / 

Orylag® p.38

171 / 172 / 174 / 185 / 186 / 209 / 216 / 219 / 222 / 

136 / 149 / 150 / 162 / 163 / 172 / 186 / 207 / 209 / 

Oxidation p.42 / 133 / 143 / 184 / 326 / 327

232 / 242 / 244 / 252 / 257 / 261 / 263 / 265 / 266 / 

Magnesium (Mg) p.44 / 46 / 47 / 134 / 

210 / 211 / 212 / 214 / 215 / 216 / 218 / 220 / 222 / 

oxo(bio)degradable p.128

270 / 283 / 285 / 289 / 295 / 297 / 299 / 301 / 302 / 

185 / 188 / 252

227 / 240 / 257 / 258 / 270 / 271 / 290 / 292 / 293 / 

Magnetic materials

p.41 / 44 / 189

295 / 297 / 298 / 299 / 300 / 301 / 304 / 305 / 306 / 

303 / 304 / 305 / 306 / 307 / 309 / 310 / 312 / 313 / 

P

314 / 315 / 319 / 321 / 322 / 325 / 326 / 327 / 331 / 

Magnetite p.44 / 189

307 / 310 / 312 / 313 / 314 / 315 / 318

Magneto-rheological p.197

Moulding, cast p.257 / 258 / 298-299

Mahogany p.248

Moulding, compression p.78

Paint p.65 / 70 / 156 / 173 / 178 / 189 / 190 / 

Plasticity p.44 / 68 / 100 / 232 / 266 / 291 / 303

Maple p.12 / 131

Moulding, contact p.78 / 212 / 301

191 / 214 / 234 / 242 / 324 / 325 / 326 / 328

Plate p.321 / 323

Marble p.6 / 169 / 190 / 195 / 207 / 236 / 339

Moulding, resin transfer 212

Palimpsest p.202

Plate tectonics p.92

Moulding, rotational

Paper p.16 / 21 / 25-32 / 125 / 126 / 133 / 139 / 

Plating p.27 / 36

p.210 / 214 / 257 / 258 / 312-313

156 / 175 / 181 / 197 / 200-201 / 247 / 257 / 262 / 

Platinum p.42 / 47

Master p.293 / 299

Moulding, vacuum p.78 / 301

263 / 265 / 266 / 270 / 281 / 283 / 289 / 291 / 303 / 

Plexiglas® p.216

Material Safety Data Sheet

Multifilament yarn p.82

317 / 319 / 321 / 322 / 326 / 327 / 332 / 349 / 350

Plumping p.36

Marls

p.185

Master model

p.299

338 / 341 / 345 / 346 / 348 / 350

Plasticiser p.68

Medium Density Fibers (MDF)

Paper pulp p.16 / 21 / 25 / 26 / 27 / 28 / 

Plywood p.2 / 70 / 74 / 76 / 175 / 177 / 199 /

p.191

201 / 247

 208 / 209 / 243 / 246 / 249 / 283 / 301 / 356

Papyrus p.26 / 202

Polishing p.94

Parchment p.26 / 202

Polyacrylic p.157

Parison p.306 / 308 / 310

Polyaddition p.66

Melamine p.39 / 158 / 175 / 282 Membrane

N

p.88 / 151 / 222 / 234 / 342 / 

344 / 353 / 359

Nacre

Mendeleïev p.181 / 224 / 337 / 362

Nanogel p.120 / 356 / 359

Particle p.107 / 108 / 139 / 142 / 162 / 192 / 

Polyamide (PA) p.69 / 70 / 74 / 82 / 86 / 

Mercury p.47 / 109

Nanometre p.343 / 358 / 359

199 / 239 / 270 / 293 / 322 / 325 / 326 / 327 / 328 / 

150 / 157 / 210 / 217 / 313 / 317 / 321 / 326 / 327

Metal Active Gaz (MAG) p.285

Nanotechnology p.46 / 65

353 / 358 / 361 / 362 / 363

Polycarbonate (PC) p.66 / 69 / 70 / 21

Metal Inerte gaz (MIG) p.285

Native state p.42 / 143 / 168 / 178

Passivation p.46 / 237 / 327

1 / 265 / 326 / 327

Metal p.41-52

Neck p.35 / 36

Pattern p.31 / 159 / 191 / 232 / 243 / 248 / 

Polychloropropene p.68 / 281

Neon p.163 / 181 / 183

250 / 266 / 269 / 292 / 293 / 294 / 303 / 321 / 

Polycondensation p.66

Metal, ‘very high-speed

Neoprene

322 / 327 / 341 / 344

Polyepoxyde p.143

deformation’ p.46

Newtonian p.197

Patterning p.131 / 243

Polyester (UP) p.66 / 69 / 70 / 74 / 76 / 

Metallic bond p.42

Nibbling p.261 / 262

Pearl p.196 / 203

82 / 86 / 128 / 147 / 149 / 150 / 157 / 195 / 207 / 

Metallurgy p.41 / 42 / 44 / 46 / 130 / 297 / 359

Nickel p.42 / 44 / 129 / 143 / 189 / 230 / 237 / 

Perfect wood / Heartwood p.11 /

212 / 215 / 234 / 240 / 281 / 282 / 289 / 301 / 

Metamaterial p.193

238 / 297 / 326 / 327

15 / 16 / 22

313 / 321 / 326

Meteorite p.41

Non-magnetic p.44 / 122 / 237 / 242 

Petrography p.92

Polyether Etherketone (PEEK)

Mica p.60 / 94 / 169 / 228

Non-newtonian

Petrology p.92

p.69 / 76 / 213

Phase Changing Materials

Polyethylene p.66 / 68 / 69 / 70 / 76 / 121 / 12 7 / 128 / 144 / 158 / 214 / 218 / 222 / 244 / 279 / 303 / 

Metal sheet

p.175 / 264

Micro-encapsulation

p.88

p.196

p.68 / 175 / 282

Non-woven

p.197

p.74 / 75 / 86 / 87 / 150 / 156 

Microfibre p.86 / 141 / 142 / 198

/ 215 / 218 / 301

(PCM) p.70 / 88

Milk casein p.88 / 127 / 128 / 151 / 282

Nubuck p.198

Phenol p.125 / 282

313 / 315 / 325 / 331

Milling p.232 / 258 / 268 / 269 / 271 / 310 / 317

Nugget p.168

Phenoplast p.281 / 282

Polyethylene terephtalate (PET)

Minerals p.54 / 92

Numbering p.82 / 84

Phosphor p.147 / 233

p.68 / 69 / 127 / 215 / 330

Mirror

Numbering

Phosphorescence

Polyethylene, high density

p.109 / 180 / 203 / 325

(HDPE) p.68 / 69 / 244

p..42 / 53 / 94 / 122 / 181 / 183 / 184 / 

194 / 235 / 317

370

p.84

Nylon® p.157 / 210

Polyethylene, low density

Pseudoplastic p.197

153 / 170 / 173 / 175 / 191 / 195 / 198 / 199 / 201 / 

Scrap metal p.44 / 45 / 238

(LDPE) p.69 / 70 / 214

Pulpwood p.16 / 22

207 / 212 / 216 / 217 / 234 / 236 / 244 / 257 / 258 / 

Seam p.92 / 285 / 289

Polylactic acid p.70 / 88 / 128

Pultrusion moulding p.78

293 / 299 / 300 / 301 / 313 / 316 / 317 / 319 / 325 / 

Sediments p.92 / 146 / 192 / 228

Polymer p.65 / 66 / 67 / 68 / 110 / 125 / 127 / 

Pumice p.92

326 / 351

Segmenting p.261

128 / 131 / 132 / 141 / 149 / 150 / 151 / 152 / 153 / 

Punching p.261 / 263

Resin Transfer Moulding (RTM)

Self-extinguishing p.69 / 152 / 210 / 211

157 / 158 / 165 / 170 / 175 / 180 / 186 / 194 / 197 / 

Pyrex®

p.78 / 212

Self-levelling concrete p.100 / 102

213 / 220 / 225 / 230 / 234 / 240 / 244 / 266 / 279 / 

Restriction of Hazardous

Self-placing concrete p.102

283 / 297 / 303 / 307 / 312 / 317 / 318 / 321 / 325 / 

Q

Substances (RoHS) p.347

Semi-conductor p.60 / 107 / 171 / 176 / 

Retification p.11 / 18 / 20 / 245

179 / 180 / 214 / 229 / 233

Retified wood p.245

Semi-crystalline p.54 / 67 / 68 / 210 / 

(PLED) p.180

Quanta p.108

Rheology p.100 / 197

213 / 214 / 218

Polymerisation p.66 / 67 / 76 / 240 / 279 / 

Quarry p.92 / 93

Rhizome p.126

Sericulture p.154

299 / 306 / 313 / 317 / 325 / 212

Quartz p.54 / 60 / 61 / 169 / 182 / 206 / 2

Ring-shaped die p.309

Sewing p.257 / 288-289

Polymethyl Methacrylate

07 / 208

Rivet p.277

Shape memory alloy (AMF)

(PMMA) p6 / 69 / 70 / 194 / 211 / 216 / 236 / 

Quartzite p.92 / 207

Roasting p.185 / 245

p.41 / 50 / 88 / 211

Rock p.56 / 91-96 / 123 / 169 / 185 / 190 / 

Sharkskin / Shagreen p.212

207 / 223 / 224 / 227 / 228 / 351

Shears p.260 / 261 / 262

Rolling device p.266

Sheet Moulding Compound

Rolling p.44 / 45 / 270 / 303 / 310

(SMC) p.78 / 212 / 258 / 301

Root p.15 / 16 / 36 / 156

Shell p.56 / 73 / 86 / 91 / 94 / 135 / 171 / 185 / 

Rosewood p.250

196 / 210 / 232 / 339 / 341

327 / 340 / 345 / 350

p.55 / 163

Polymer Light-Emitting Diode

265 / 279 / 281 / 309 / 315 / 327

Polyolefin p.281 / 214 / 218 Polyoxymethylene (POM)

R

p.69 / 217

Radioactive

p.58 / 108 / 132 / 163 / 348

Polypropylene (PP)

141 / 150 / 158 / 218 / 222 / 240 / 266 / 317 / 326

Raised print

p.321

Polystyrene (PS) p.66 / 69 / 70 / 76 / 119 

Rare earths p.114 / 189 / 224 / 352

Rotary cutting p.18 / 19 / 131 / 243

Shore p.234

/ 158 / 194 / 219 / 262 / 293 / 315 / 327

Rays p.15 / 55 / 58 / 108 / 145 / 178 / 193 / 

Routing p.258 / 270 / 271

Shot-blasting p.325 / 328

Polystyrene, crystal p.219

325 / 359

Rubber (NR) p.16 / 38 / 68 / 69 / 225 / 

Shrinkage p.16 / 17 / 18 / 20 / 68 / 76 / 122 / 

Polystyrene, expanded (PSE)

Reaction Injection Moulding

240 / 281 / 321 / 340

141 / 149 / 162 / 245 / 273 / 283 / 299 / 305 / 313 / 

p.219

(RIM) p.212 / 306

Ruby p.148 / 223 / 226  

326 / 324

Polystyrene, high-impact (HIPS)

Rebate

Rust p.46 / 325 / 326 / 327

Silica carbonate p.62

p.219

Recyclability

Polytetrafluorethylene (PTFE)

150 / 235 / 238 / 240 / 244 / 347 / 348 / 349

p.69 / 220

Recycling p.14 / 20 / 25 / 26 / 28 / 44 / 56 / 

S

142 / 153 / 167 / 227 / 233 / 270 / 325 / 356

Polyurethane (PU) p.68 / 69 / 70 / 158 / 

65 / 66 / 68 / 70 / 78 / 183 / 205 / 224 / 229 / 

221 / 240 / 281 / 282 / 306 / 313 / 326

330-332 / 325 / 345 / 349-355

Salt p.34 / 66 / 92 / 145 / 188

Silicon (Si) 50 / 66 / 76 / 114 / 132 /137 / 

Polyvinyl Chloride (PVC)

Red ironwood p.246

Salting / Curing p.26 / 34 / 66 / 76 / 100 / 102

 204 / 205 / 206 / 229 / 233 / 234

66 / 68 / 69 / 222 / 281 / 313

Reduction

Sand jet p.233 / 262 / 263

Silicone (SI) p.66 / 68 / 69 / 70 / 233 / 234 / 

Polyvinyl

205 / 251 / 326 / 332

p.66 / 69 / 70 / 78 / 

p.165 / 222

p.370

Silica p.53 / 54 / 55 / 60 / 62 / 74 / 120 / 136 / 

p.11 / 14 / 41 / 56 / 122 / 128 / 

p.18 / 42 / 100 / 122 / 128 / 

Silica smoke p.142 Silicate p.56 / 92 / 148

Sand p.54 / 56 / 78 / 92 / 100 / 101 / 130 / 140 / 

240 / 281 / 282 / 299 / 321 / 340

Poplar p.245 / 247 / 247

Reeling p.82

142 / 162 / 163 / 195 / 196 / 197 / 227 / 233 / 261 / 

Silk crepe p.154

Porcelain p.60 / 61 / 138 / 207 / 227 / 326

Refractive index p.55 / 145 / 146 / 193

262 / 263 / 266 / 270 / 293 / 292 / 328 / 346

Silk p.30 / 81 / 82 / 84 / 86 / 88 / 135 / 154 / 

Porosity p.94 / 279 / 297 / 142 / 190 / 227

Refractory p.60 / 61 / 62 / 76 / 138 / 187 / 

Sandblasting p.162 / 270 / 325 / 328

160 / 164 / 289 / 321

Pottery p.54 / 60

195 / 292 / 299 / 303 / 315

Sandstone / Stoneware p.60 / 92 / 

Silk worm p.154

Power hammer p.295

Registration, Evaluation and

94 / 136 / 138 / 227 / 326

130 / 131 / 143 / 168 / 194 / 235 / 241 / 284 / 

Silver (Ag) p.42 / 44 / 46 / 47 / 114 / 129 / 

Authorisation of Chemicals

Sandstone, drawn p.227

Pre-preg p.301

(REACH) p.347 / 348

Sandstone, enameled p.227

285 / 286 / 353

Pre-stressed concrete p.140

Reinforced concrete p.78 / 102 / 

Sandstone, vitrified p.227

Silviculture p.14

Precious stone p.96 / 145 / 148 / 223

103 / 140 / 141 / 153

Sandwich p.73 /76 /78 /121 /133 /149 /158 /

Single filament p.82

Preform p.295 / 297 / 306

Reinforced Reaction Injection

165 /170 /177 /208 /250

Single thread p.28 / 83

Press p.263 / 265 / 279 / 290 / 295 / 310 / 321

Moulding (RRIM) p.306

Sapphire p.148 / 223 / 226

Sintering p.62 / 220 / 257 / 258 / 269 / 

Primer p.86

Reinforcement p.74 / 76 / 78 / 88 / 102 / 

Sapwood p.15 / 16 / 18 / 246 / 247 / 248 / 

296-297 / 318

Printing

103 / 140 / 141 / 152 / 153 / 301 / 306 / 313 / 359

249 / 250

Sintering, laser p.297 / 318

180 / 200 / 201 / 303 / 318 / 320-323 / 327 / 328

Renewable

Satin p.84 / 85 / 289 / 324

Skaï® p.37

Printing, silkscreen p.322

205 / 347 / 349 / 350

Saw p.20 / 74 / 94 / 140 / 227 / 260 / 261 / 

Skin p.26 / 33-40 / 152 / 158 / 159 / 166 / 198 / 

Printing, stamp p.301

Rheopectic p.197

262 / 263 / 270 / 309 / 337 / 343 / 362

202 / 221 / 231 / 257 / 263 / 282 / 289 / 291 / 303 / 

Programme for the

Resilience p.42

Sawing p.17 / 18 / 94 / 121 / 244 / 246 / 

Endorsement of Forest

Resin concrete p.100

261 / 262 / 315

Slab p.45 / 93 / 124 / 227 / 228 / 268 / 340

Certification (PEFC) p.348

Resin p.11 / 16 / 18 / 37 / 70 / 74 / 76 / 77 / 78 / 

Schist p.92 / 136 / 228

Slate p.94 / 228

Prototyping

100 / 107 / 125 / 127 / 139 / 144 / 149 / 150 / 152 / 

Scoring p.263 / 266

Slicing p.18 / 19

Power

p.108 / 109

p.36 / 86 / 121 / 147 / 177 / 178 / 

p.305 / 317 / 318

p.14 / 78 / 126 / 127 / 128 / 144 / 

306 / 325 / 327 / 350 / 353 / 341 / 342 / 344

371

Slide p.66 / 232 / 305

Surfacing p.50 / 270

Transparency p.53 / 54 / 55 / 78 / 120 / 

Slip p.60 / 62 / 136 / 160 / 289 / 297 / 298 / 

Supercooling p.54 / 161

149 / 167 / 211 / 216 / 232 / 234 / 325 / 338 / 339

299 / 306 / 361

Sustainability p.11 / 38 / 88 / 126 / 155 / 

Tree p.11 / 12 / 13 / 14 / 15 / 16 / 18 / 26 / 

Slipcasting p.298-299

345 / 347 / 349 / 354 / 

34 / 38 / 68 / 131 / 134 / 142 / 144 / 156 / 173 / 

Soda p.54 / 163

199 / 201 / 203 / 209 / 208 / 225 / 243 / 245 / 246 / 

Sodium p.54 / 55 / 108 / 109 / 110 / 114 / 172 / 183

250 / 340 / 346

Soft p.15 / 16 / 18 / 26 / 34 / 37 / 38 / 56 / 61 / 65 / 

T

Tree trunk p.14 / 15 / 16 / 131 / 243 Triply® p.199

66 / 82 / 92 / 94 / 132 / 135 / 152 / 154 / 159 / 171 /  177 / 185 / 187 / 225 / 241 / 247 / 249 / 250 / 262 / 

Tannin p.16 / 33 / 36 / 38 / 283

Truing p.270

263 / 265 / 285 / 315 / 325 / 338 / 340

Tanning p.36 / 37 / 38 / 198

Tungsten Inert Gas (TIG) p.130 / 285

Sol-gel p.56 / 58 / 356

Tarmac p.123

Tungsten p.110 / 114 / 182 / 184 / 261 / 263 / 

Soldering p.178 / 241 / 273 / 284 / 285

Teak p.249 / 325

269 / 285 / 297

Solid surfaces p.236

Techno-sciences p.108 / 337 / 343

Turtle p.232

Spark erosion

Teflon®

Twill p.75 / 84 / 85

p.270

p.220 / 265

Spindle p.82 / 153 / 271

Tempering p.46 / 56 / 238

Typography p.320 / 321

Spinneret p.82 / 83 / 86 / 151 / 152 / 157

Tenon p.270 / 274

Tyvek® p.30 / 318

Spinning p.82

Tergal® p.157 / 215

Spraying p.102 / 173 / 212 / 301 / 325 / 327

Terra cotta p.60 / 299

Spring p.140 / 217 / 266

Tex p.84 / 88

Spring-back p.265

Textile p.16 / 81-88 / 102 / 152 / 156 / 165 / 

Spruce p.11 / 13 / 245 / 246

170 / 198 / 210 / 257 / 263 / 266 / 289 / 301 / 351

Ultra high performance

Staff p.207

Texturing p.82

concrete p.138

Stainless steel p.44 / 46 / 50 / 189 / 222 / 

Theory of energy bands p.229

Ultra-low Voltage (ULV) p.112

237 / 238 / 242 / 265 / 325 

Thermochromic p.251 / 342

Ultrasound p.62 / 206 / 211 / 215 / 216 / 

Stains p.36 / 198 / 283 / 326

Thermoforming p.119 / 211 / 219 / 222 / 

217 / 261 / 262 / 263

Staking p.36

257 / 258 / 309 / 314-315

Ultraviolet p.30 / 55 / 108 / 109 / 181 /  203 / 251

Stamping p.7 / 129 / 253 / 257 / 258 / 

Thermoplastic elastomer (TPE)

Up-cycling p.331

290-291 / 295 / 303

p.68 / 69 / 240

Starter p.111 / 181 / 183

Thermoplastic

Steel metallurgy p.41 / 44

66 / 67 / 68 / 69 / 70 / 74 / 76 / 119 / 128 / 135 / 

Steel p.11 / 14 / 27 / 41-50 / 62 / 70 / 76 / 78 / 

156 / 157 / 210 / 211 / 212 / 213 / 214 / 215 / 216 / 

100 / 103 / 122 / 125 / 130 / 134 / 140 / 141 / 154 / 

217 / 218 / 219 / 220 / 221 / 222 / 240 / 244 / 262 / 

Vacuum coating p.327

162 / 174 / 189 / 222 / 237 / 238 / 313 / 325 / 326 / 

265 / 266 / 282 / 285 / 303 / 305 / 306 / 307 / 309 / 

Vacuum sublimation p.327

327 / 337 / 340 / 342 / 349

310 / 312 / 313 / 314 / 315 / 317 / 348

Valence p.229

Thermoset

Van der Waals p.66 / 67 / 279

Stereolithography

p.316 / 317

Wafer p.76 / 204 / 233 Walnut p.12 / 131 / 247 Warp p.84 / 86 / 87 / 247 / 270 Warping p.18 / 19 / 175 / 262 Washi p.201 Water jet p.260 / 261 / 262 / 263 / 318 Watermark p.28 / 30 Watts p.108 Wave p.94 / 107 / 108 / 193 / 358 / 363 Wavelength p.108 / 176 / 359 Wax p.162 / 198 / 293 / 292 Weave p.84 / 85 Weaving p.81 / 84 / 85 / 86 / 88 / 126 / 160 Weft p.84 / 86 /87 Wenge p.248

U

Wet-blue p.36 Wettability p.248 / 359 Whiteness p.27 / 28 / 172 / 196 / 201 Wild cherry p.247 Wood derivatives p.20 / 177 / 270 Wood p.7 / 11-22 / 25 / 26 / 28 / 36 / 65 / 66 /  70 / 74 / 76 / 86 / 88 / 100 / 102 / 125 / 131 / 135 /  139 / 151 / 156 / 172 / 173 / 174 / 175 / 177 / 191 /  199 / 208 / 209 / 225 / 236 / 243 / 244 / 245 /  246-50 / 257 / 261 / 263 / 265 / 266 / 269 / 270 /  271 / 272 / 273 / 274 / 275 / 281 / 283 / 301 / 315 / 

p.16 / 22 / 60 / 62 / 65 / 

p.66 / 67 / 68 / 70 / 74 / 77 / 

V

Stitch p.33 / 38 / 84 / 86 / 288 / 289

78 / 125 / 139 / 149 / 175 / 199 / 212 / 213 / 

Vanadium p.44 / 47 / 114 / 237 / 242

Stone p.7 / 60 / 65 / 66 / 91-96 / 99 / 100 / 124 / 

215 / 221 / 225 / 240 / 282 / 299 / 301 / 305 / 

Varnish p.20 / 46 / 70 / 86 / 129 / 135 / 156 / 

132 / 136 / 138 / 145 / 148 / 169 / 185 / 190 / 198 / 2

306 / 310 / 313

177 / 190 / 194 / 202 / 212 / 221 / 234 / 246 / 249 / 

07 / 212 / 223 / 227 / 228 / 257 / 261 / 262 / 263 / 27

Thixiotropifier p.326

245 / 325 / 326 / 327 / 328

0 / 326 / 328 / 337 / 339 / 340 / 351 / 340 / 341 / 351

Thixotropic p.197

Veining p.171 / 190 / 243 / 248 / 249 / 250

Strain-hardening p.46 / 47 / 303

3D printing p.318

Vellum p.26 / 200 /202

Strass

Throwing

Velvet p.84 / 198 / 327

p.55 / 145

W

p.82

317 / 321 / 322 / 325 / 326 / 327 / 328 / 338 / 341 /  346 / 348 / 349 / 350 / 352 / 356

Wood polymers p.11 / 22 / 244 Wood species p.16 / 174 / 199 / 246-250 Wool p.18 / 34 / 36 / 37 / 56 / 82 / 84 / 86 / 96 /  150 / 151 / 154 / 156 / 160

Workpiece p.261 / 262 / 270 / 285 / 286 /  295 / 326 / 327 / 328

X XX-Chromatic p.251

Stratification p.92 / 301

Tile p.60 / 61 / 62 / 102 / 123 / 136

Veneer p.18 / 19 / 22 / 76 / 92 / 126 / 131 / 139 / 

Stratoconception® p.318 / 319

Tin (Sn) p.42 / 44 / 47 / 56 / 57 / 114 / 120 / 

175 / 177 / 191 / 208 / 209 / 232 / 236 / 243 / 247 / 

Structural woodwork p.246 / 248 

129 / 130 / 143 / 178 / 194 / 241 / 253 / 284 / 

248 / 249 / 250 / 283

Stucco p.190 / 207

285 / 327

Vent holes p.299

Yarn p.74 / 82 / 83 / 84 / 86 / 151 / 154

Stump p.16 / 53 /131

Tinning p.194 / 241

Vermeil p.168

Yarn production p.82

Style p.25 / 86 / 266 / 321 / 351

Tinplate p.241

Violet wood p.12 / 250

Subcutaneous tissue p.34 / 35 / 36

Titanium (Ti) p.42 / 46 / 47 / 50 / 58 / 

Virtuality p.81 / 107 / 263 / 339 / 342 /  346 / 347

Suede p.28 / 36 / 37 / 198 / 327

104 / 144 / 122 / 186 / 189 / 226 / 229 / 230 / 

Viscoplastic p.197

Suedine p.198

242 / 297 / 339

Viscose p.82 / 86 / 135 / 151

Super alloy p.41 / 46

Top log p.15

Viscosity p.54 / 55 / 60 / 100 / 197 / 326

Superconductor p.41 / 50 / 239

Translucence p.36 / 55 / 58 / 60 / 96 / 99 / 

Vitreous state p.53 / 54

Zinc p.44 / 46 / 47 / 114 / 122 / 129 / 130 / 143 / 

Surface treatment p.28 / 58 / 74 / 129 / 

102 / 142 / 146 / 167 / 171 / 201 / 202 / 214 / 218

Vitrification p.58 / 145 / 326

161 / 178 / 230 / 238 / 252 / 253 / 286 / 305 / 325 / 327

164 / 168 / 186 / 202 / 235 / 325 / 342

Transmutation p.91 / 178

Vulcanisation p.240 / 325

Zirconia p.60 / 62

372

Y

Z Zamak alloy p.47 / 252 / 253

Frame Publishers Amsterdam www.frameweb.com Birkhäuser Verlag GmbH Basel www.birkhauser.com

Directed by matériO www.materio.com Authors Daniel Kula and Élodie Ternaux Associated author Quentin Hirsinger Graphic design (with illustrations) Général Design, Maroussia Jannelle with Benjamin Gomez This book contains the fonts Swiss 721 BT, and Materiology for the titles Photographers Théo Mercier (Part 01) Véronique Huyghe (Part 02) except: Carbon p.132 © Buriy (Fotolia) Diamond p.146 © Tom (Fotolia) Emerald p.148 © Imfoto Gallium p.161 © 2012 Theodore Gray, periodictable.com Lithium p.187 © Coprid (Fotolia) Magnesium p.188© Warut Roonguthai Metamaterials p.193 © CNRS Photothèque, Stefan Enoch / UMR6133 - Institut Fresnel Marseille Mercury p.192 © Cerae (Fotolia) Non-Newtonian fluids p.197 © Unpict (Fotolia) Rare earths p.224 © 2012 Theodore Gray, periodictable.com Ruby & sapphire p.226 © Xshd and winterling Semiconductors p.229 © Vetkit and borissos (Fotolia) Superconductors p.237 © Alan Crawford

Special thanks to Sofia Chaoui, Anne-Sabine Henriau, Raymond van Kooyk, Denis Laville, Lise Maginot and Morgane Rébulard

Distribution ISBN 978-3-03821-254-6 Birkhäuser Verlag GmbH Basel PO Box 44 / CH – 4009 Basel Part of de Gruyter www.birkhauser.com This book is also available in German (ISBN 978-3-03821-238-6), French (ISBN 978-3-0346-0819-0) and Dutch (ISBN 978-90-77174-97-5) The original hardcover edition (first print in 2008) is available English (978-3-7643-8424-1).

Production Sarah de Boer-Schultz and Marlous van Rossum-Willems Translation TransL Vertaalbureau (Rebecca Parker, Clive Pygott, Andrew James and Liz van Gerrevink) Copy editing Clare Lowther and John Bezold Colour reproduction NerocVGM and Edward de Nijs (Frame) Printing D’Print

375

© 2014 Frame Publishers © 2014 Birkhäuser Verlag GmbH Basel

377

Bibliographic information published by Die Deutsche Nationalbibliothek. Die Deutsche Nationalbibliothek lists this publication in the Deutsche Nationalbibliografie; detailed bibliographic data is available in the internet at http://ddb.de. This work is subject to copyright. All rights reserved. No part of this publication or the information contained herein may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, by photocopying, recording or otherwise, without prior written permission from the publishers. Compiler(s) and publisher are fully aware of their responsibility to produce a publication which is as reliable as possible. Nevertheless they cannot be held liable for inaccuracies and/or deficiencies which may possibly occur in this publication. Printed on acid-free paper produced from chlorine-free pulp. TCF ∞ Printed in Singapore 987654321

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