Metalworking Technology and Deterioration of Jin Bronzes from the Tianma-Qucun Site, Shanxi, China 9781841714042, 9781407324067

Table of contents :
Front Cover
Title Page
Copyright
Dedication
Abstract
Acknowledgements
Table of Contents
List of Figures
List of Tables
CHAPTER 1: INTRODUCTION
CHAPTER 2: THE CHINESE BRONZE AGE AND JIN BRONZES
CHAPTER 3: THE SITE OF TIANMA-QUCUN
CHAPTER 4: DOCUMENTATION AND ANALYTICAL TECHNIQUES
CHAPTER 5: TECHNICAL STUDY OF THE METALS
CHAPTER 6: ANALYTICAL RESULTS OF CORROSION PRODUCTS AND SOILS
CHAPTER 7: COMPARATIVE STUDIES OF BRONZE COMPOSITION
CHAPTER 8: CONCLUSIONS
Figures and Tables
Appendix I: Names ofthe Western Zhou Lords ofJin
Appendix II: Names of Chinese Bronze Objects
Appendix III: Names of Geographic Locations, Sites, and Cultures
References
METALWORKING TECHNOLOGY AND DETERIORATION OF JIN BRONZES FROM THE TIANMA-QUCUN SITE, SHANXI, CHINA: CATALOGUE
LIST OF CATALOGUE
INTRODUCTION
CATALOGUE

Citation preview

l na tio ne di nli ad l o ith ria W ate m

BAR  S1023  2002   WANG   METALWORKING TECHNOLOGY AND DETERIORATION OF JIN BRONZES

Metalworking Technology and Deterioration of Jin Bronzes from the Tianma-Qucun Site, Shanxi, China Quanyu Wang

BAR International Series 1023 9 781841 714042

B A R

2002

Metalworking Technology and Deterioration of Jin Bronzes

from the Tianma-Qucun Site, Shanxi, China Quanyu Wang

BAR International Series 1023 2002

ISBN 9781841714042 paperback ISBN 9781407324067 e-format DOI https://doi.org/10.30861/9781841714042 A catalogue record for this book is available from the British Library

BAR

PUBLISHING

To my daughter Toni

ABSTRACT The subject of this research project is the technical study of excavated bronze fragments from the Tianma-Qucun site. This site is located in southwest Shanxi province, China. It was identified as an early capital of the Jin state in the periods of the Westem Zhou and early Spring and Autumn, i.e. 1027-650 BC. This study aims to provide new metallurgical data on Jin bronzes, specifically on casting techniques and the deterioration of these bronzes in their burial environment. Corrosion study helps guide investigative cleaning and conservation treatments of these bronze objects. Comparing the bronzes from the elite tombs with those from other tombs reveals social differences within the Jin culture. Forty-seven bronze fragments have been sampled for technical study. Both metal and corrosion products have been examined to characterise casting techniques and corrosion. Six soil samples and two water samples from this site have also been analysed for preliminary evaluation of burial environment conditions. The analytical techniques used in this research include metallography, scanning electron microscopy, electron probe microanalysis, atomic absorption spectrophotometry, X-ray diffraction, differential thermal analysis, and differential scanning calorimetry. All analysed objects were cast, of which 45 are tin bronzes, two unalloyed copper, one tin, and one lead. Objects from the elite tombs are mainly binary alloys, while most objects from other tombs are leaded bronzes. The degree of corrosion varies among these samples; most are severely corroded. Objects from the elite tombs were better preserved than those from other tombs. The burial conditions were slightly alkaline. No evidence of artificial patination has been observed. Malachite, cuprite, azurite and cerussite are the most common corrosion products. A sulphur-rich passivating black layer is frequently present in the surface corrosion. Redeposited copper is also very common. Nantokite has been observed on a few samples although chlorides have rarely been seen. Most of these objects should remain stable under recommend relative humidity storage conditions.

ACKNOWLEDGEMENTS First of all I would like to thank Dr. John Merkel, my supervisor, for all the help he has given to me during the course of my study. He introduced many experts and colleagues to me, which has helped me to build communication in the field of archaeometallurgy. I am greatly indebted to Mr. Tom Chase, the former head of the Department of Conservation and Scientific Research, Freer gallery of Art, Smithsonian Institution, for his great encouragement and strong recommendation. During one year of working with him as a Forbes Fellow as well as a beginner in the field of archaeometallurgy in the Freer Gallery, he taught me how to document the data, how to observe the corrosion products, how to section and mound the samples, etc. I was really impressed by his tremendous enthusiasm for this subject. I could not thank him enough for his help with my UK visa application and delivery of materials and data from Washington DC to London. I always got his support whenever I needed it. I am very grateful to the Institute of Archaeology for the Getty Scholarship and Tylecote Fellowship, which provided the majority of funding for my study. I must thank Dr. Wang Tao and Dr. Elisabeth Bacus, my other two supervisors, for their advice on cultural aspects of this research and their support in my writing up. Dr. Wang Tao has provided me some Chinese references for my comparison study. Dr. Elisabeth Bacus has kindly read through the manuscript of this monograph and provided detailed comments. I am very grateful to Professor Thilo Rehren of the Institute of Archaeology for his comments and advice on this study. Grateful thanks are also due to Dr. Anna Bennett and Dr. Ian Glover. Dr. Anna Bennett provided her generous help with my catalogue. Dr. Ian Glover provided his encouragement and guidance at the beginning of my PhD study. I am grateful to Mr. Kevin Reeves for his help with SEM/EDS, EPMA, XRD and other analytical techniques. He was always patient in answering my questions and solving the problems encountered in the course of my analysis; he tried many ways to get the correct results. I am also grateful to Dr. Marianne Odlyha of Chemistry Department at Birkbeck College for her help with TGA and DSC for the analyses of soil and mould samples. I would also like to thank professor Shao Hongxiang of the Department of Geology at Peking University for his help with ICP-AES analysis of the soil samples and analysis of water samples. I would like to thank all the staff of the Department of Conservation and Scientific Research, Freer Gallery of Art, Smithsonian Institution, for their help with my work during the period I worked there. Their friendship and kindness will always be remembered. I would like to thank Professor Li Boqian, the Director of the Archaeology Department, Peking University, for allowing me to study these samples. I am grateful to many of my colleagues in the Department for their help, especially Professor Su Bai, Zou Heng, Chen Tiemei, Yuan Sixun, and Xu Tianjin. Next I must thank Professor Zhou Baozhong, the former director of the Conservation Department, the National Museum of Chinese History, Professor Han Rubin, Head of Institute of Historical Metallurgy and Materials, Beijing University of Science and Technology, Professor Hua Jueming of Institute of Natural Science History, Chinese Academy of Science, for their support and advice. Thanks also go to Dr. David A. Scott, Dr. James A. Charles, Dr. Paul T. Craddock, Dr. Peter Northover, Dr. Luc Robbiola, Dr. Jessica Rawson, Professor Hans G. Bachmann, and Professor Beno Rothenberg for their advice and support. I would like to thank Dr. David Davison for his help with the publication of this monograph. Finally, I would like to thank my parents and my sister for their love and support. But my warmest thanks must go to my husband, Dr. Qiu Zhengxiang, and my daughter Toni. It would not have been possible for me to carry out the research for more than four years abroad without their understanding and patience. I would not have been here without my husband's encourage and support. My daughter's love has been also the driving force of my studying. Each reunion has been the happiest of moments in our life during the period of my PhD study.

CONTENTS ACKNOWLEDGEMENT LIST OF FIGURES LIST OF TABLES

1

v vn

CHAPTER 1 INTRODUCTION

1

CHAPTER 2 2.1 2.2 2.3 2.4

THE CHINESE BRONZE AGE AND JIN BRONZES The Chinese Bronze Age Brief History of the Jin state Jin Bronzes Summary

3 3 6 7 8

CHAPTER 3 3.1 3.2 3.3 3.4

THE SITE OF TIANMA-QUCUN Archaeological Investigation of Early Jin Culture at the Site The Excavation of the Elite Tombs of Early Jin The Details of Tombs M33, M91, M92 and M93 Summary

10 10 11 12 14

CHAPTER 4 DOCUMENTATION AND ANALYTICAL TECHNIQUES 4.1 Introduction 4.2 Sampling 4.2.1 Principle of Sampling 4.2.2 Sampling Strategies for this Project 4.3 Physical Properties of the Bronze Fragments 4.3.1 Surface Observation of Bronze Fragments 4.3.2 Microhardness Examination 4.3.3 Grain Size 4.4 Examination of Corrosion Products 4.4.1 Morphology 4.4.2 X-ray Diffraction 4.4.3 Composition 4.5 Metallography 4.5.1 Theory 4.5.2 Preparation of the Samples 4.5.3 Etching of the Samples 4.6 Compositional Analysis 4.6.1 Introduction 4.6.2 Bulk Chemical Analysis: AAS and ICP-AES 4.6.3 Microanalysis: SEM/EDS and EPMA 4. 7 Analysis of Soil and Water Samples 4.7.1 Compositional Analysis of the Soil Samples 4.7.2 pH and Redox Potential Measurement of the Soil Samples 4.7.3 pH Measurement and Compositional Analysis of the Water Samples 4.8 Summary

15 15 15 15 15 17 17 18 18 18 18 18 22 22 22 22 23 23 23 23 24 27 27 27 28 28

CHAPTER 5 TECHNICAL STUDY OF THE METALS 5.1 Introduction 5.2 Metallographic Observation 5.2.1 Micro structure 5.2.2 Grain size

29 29 29 29 31

ii

5.3 Mould Materials 5.4 Composition 5.4.1 Estimate of Bulk Analysis: Results of Atomic Absorption Spectrophotometry 5.4.2 Microanalysis 5.5 Discussion 5.5.1 Summary of Composition of Jin Bronzes 5.5.2 Discussion of the "Six Formulae" 5.6 Summary

31 33 33 34 35 35 37 40

CHAPTER 6 ANALYTICAL RESULTS OF CORROSION PRODUCTS AND SOILS 6.1 Introduction 6.2 Burial Environment 6.2.1 The Effect of Burial Construction on Preservation of Metals 6.2.2 Analytical Results of the Soil Samples 6.3 Corrosion Morphology 6.3.1 Surface Observation 6.3.2 XRD Results of Corrosion Products 6.3.3 Microstructures of the Corroded Metal 6.4 Selective Corrosion 6.4.1 Equi-axed structures 6.4.2 Dendritic structures 6.5 Oxides and Carbonates 6.5.1 Cuprite 6.5.2 Cassiterite 6.5.3 Malachite and Azurite 6.5.4 Corrosion of Lead 6.5.5 Fe-rich Corrosion Products 6.6 Sulphates and/or Sulphides 6.6.1 Sulphates/ Sulphides in the Outer Layer of Corrosion 6.6.2 Sulphates/ Sulphides in the Black Layer 6.6.3 Discussion 6.7 Redeposited Copper 6.7.1 Introduction 6.7.2 Redeposited Cu on the Jin Bronzes 6.7.3 Discussion 6.8 Chlorides 6.8.1 Introduction 6.8.2 Chlorides on the Jin Bronzes 6.8.3 Discussion 6.9 Conservation aspects 6.9.1 Bronze Disease 6.9.2 Black Layer 6.10 Summary

41 41 41 41 42 46 46 47 48 49 49 49 50 51 51 52 52 53 53 53 53 54 56 56 58 58 59 59 60 60 61 61 61 61

CHAPTER 7 COMPARATIVE STUDIES OF BRONZE COMPOSITION 7.1 Introduction 7.2 Jin Bronzes from Elite Class and Non-elite Classes 7.2.1 Bronzes From the Tomb of Jin State Minister Zhao 7.2.2 Summary of the Jin Bronzes 7.3 Jin Bronzes and Bronzes From Other Chinese states 7.3.1 Compositions of Bronzes From Different Cultures and Periods in China

63 63 63 63 64 65 65

iii

7.3.2 Discussion 7.4 Summary

76 77

CHAPTER 8 CONCLUSIONS 8.1 Metalworking Technology of the Jin Bronzes 8.2 Corrosion of Jin Bronzes 8.3 Comparison Study 8.4 Topics for Further Study

78 78 78 79 79

FIGURES AND TABLES (colour figures are reproduced on CD)*

81

APPENDIX I Names of the Western Zhou Lords of Jin APPENDIX II Names of Chinese Bronze Objects APPENDIX ill Names of Geographic Locations, Sites, and Cultures

139 139 140

REFERENCES

141

CATALOGUE (full catalogue reproduced in colour on CD)*

149

Please note that the CD referred to above has now been replaced with a download available at www.barpublishing.com/additional-downloads.html

iv

LIST OF FIGURES Figure 2.1 Figure 2.2 Figure 2.3 Figure 3.1 Figure 3.2 Figure 3.3 Figure 3.4 Figure 3.5 Figure 3.6 Figure 3.7 Figure 4.1 Figure 4.2 Figure 4.3 Figure 4.4 Figure 5.1 Figure 5.1 Figure 5.3 Figure 5.4 Figure 5.5 Figure 5.6 Figure 5.7 Figure 5.8 Figure 5.9 Figure 5.10 Figure 5.11 Figure 5.12 Figure 5.13 Figure 5.14 Figure 5.15 Figure 5.16 Figure 5.17 Figure 5.18 Figure 5.19 Figure 5.20 Figure 5.21 Figure 6.1 Figure 6.2 Figure 6.3 Figure 6.4 Figure 6.5 Figure 6.6 Figure 6.7 Figure 6.8 Figure 6.9 Figure 6.10 Figure 6.11 Figure 6.12 Figure 6.13 Figure 6.14 Figure 6.15 Figure 6.16 Figure 6.17 Figure 6.18 Figure 6.19 Figure 6.20

Piece-mould casting process of a bronze zhi Map of provinces in China Jin state in the Eastern Zhou period Location of the Tianma-Qucun site in Shanxi province The Tianma-Qucun site Four culture layers of pit 3 at the Tianma-Qucun site Characteristic pottery types of the eight phases of Jin culture at the Tianma-Qucun site Location of the cemetery of Jin lords Layout of the graves and chariot pits (Kl-K6) in the cemetery of the lords of Jin Schematic representation of construction of M93 XRD spectrum of cerussite taken from corrosion products on M6195:20 Schematic diagram showing different background appearance of Ka and La of As TG and DTG curves for calcium oxalate monohydrate Typical DTA or DSC curve Histogram for wall thickness of Jin vessels Histogram for wall thickness or diameter of Jin horse fittings Sketchmaps of horse fittings Binocular microscopic picture of Houma mould of tool Petrographic thin section of Houma mould of tool Binocular microscopic picture of Houma mould of vessel Petrographic thin section of Houma mould of vessel Binocular microscopic picture of Western Zhou core of vessel from Shaanxi Petrographic thin section of W estem Zhou core of vessel from Shaanxi SEI of polished section of Houma mould of tool SEI of polished section of WZH mould of vessel from Shaanxi Multiplots of DSC curves Quartz peak in Houma mould of vessel XRD spectrum of the mould of Houma vessel Cooling rate for a Cu - 10% Pb - 10% Sn bronze cast in metal, stone and clay moulds preheated to 100°C and air cooled after casting Scatterplots for Jin metals Scatterplots for Jin vessels and horse fittings from the elite tombs Histogram for Sn for Jin vessels from the elite tombs Histogram for Sn for Jin horse fittings from the elite tombs Comparison scatterplots for Jin metals from different elite tombs Mechanical properties of bronzes Photograph of metallographic section of M6231: 1 Profile of No 1 Han tomb at Mawangdui, Changsha TGA plots of soil from M91 and M93 DSC curves of soils run in oxygen The state of preservation of the original Surface of the Jin bronzes Typical structure of a corroded Jin bronze Two types of structures of corrosion overburden Microstructures of the corroded metal from Tianma-Qucun Corroded eutectoid beyond the original dimension Schematic representation of the passive structure of bronzes SEM/EDS colour maps oflead corrosion in the overburden ofM64:148 Pseudomorph of lead inclusions in the metal SEM/EDS colour maps of Fe-rich corrosion layer on M91: 13 7A Photomicrograph of crystalline copper sulphides with fractures in the corrosion overburden on M91:506A Two types of black layers on the Jin bronzes from Tianma-Qucun SEM/EDS colour maps of corrosion at the surface ofM91 :506A Photomicrograph of the black layer on M91:506A EPMA linescans traversing the metallographic section ofM91:506A Pourbaix diagram ofCu-H-0-S system Different types of secondary metallic copper in Jin bronzes

V

81 82 83 84 85 85 86 87 87 88 89 89 90 90 93 93 94 95 95 96 96 97 97 98 98 98 99 100 101 102 103 104 104 105 106 108 108 109 110 111 112 112 113 114 114 115 116 117 118 119 120 121 122 122 123

Figure 6.21 Figure Figure Figure Figure Figure Figure

6.22 6.23 7.1 7.2 7.3 7.4

Appo:ximate position of some natural environment (A) and stable corrosion products of bronze objects (B) in the Eh-pH diagram. Pourbaix diagram ofCu-H-0-Cl system Histogram of corrosion grades for Jin bronzes from Tianma-Qucun Profile of the tomb of the Jin state minister Zhao Boxplots for Jin bronzes Boxplots for Shang bronzes from Jinxu Boxplots for Chu bronzes

vi

124 124 125 133 134 135 136

LIST OF TABLES Table 2.1 Table 2.2 Table 2.3 Table 2.4 Table 3.1 Table 4.1 Table 4.2 Table 4.3 Table 4.4 Table 4.5 Table 4.6 Table 4.7 Table 4.8 Table 5.1 Table 5.2 Table 5.3 Table 5.4 Table 5.5 Table 5.6 Table 5.7 Table 6.1 Table 6.2 Table 6.3 Table 6.4 Table 6.5 Table 6.6 Table 6.7 Table 6.8 Table 6.9 Table 7.1 Table 7.2 Table 7.3 Table 7.4 Table 7.5 Table 7.6 Table 7.7 Table 7.8 Table 7.9 Table 7.10 Table 7.11 Table 7.12 Table 7.13

Periods of the Chinese Bronze Age and Summary of Characteristic Bronze Features Checklist of the Chinese Bronze Age Three schools of interpretation of the ancient texts of the "Six Formulae" The Western Zhou lords of Jin The dates of the tombs proving the bronze samples Definition of degree of deterioration of the archaeological bronze artifacts Examined bronze fragments and technique checklist Composition and ratio of elements of selected corrosion products Crystal structure and colour of minerals often found in corrosion products AAS conditions WD spectrometers and their interplanar spacing (2d(A)) used in JXA- 8600 Selected WD spectrometer lines and standards used in the analysis Minimum detection limit for EPMA analysed elements Measurements of the metals Physical properties and TGA results of the mould samples SEM / EDS results of the mould samples Quartz contents of mould samples Elemental composition of metals by AAS Best estimated compositions and alloy types of the Jin bronzes from Tianma-Qucun Main alloy components of metal objects from the Jin elite tombs The proportions of clay particle size in loess from different parts of China Results of analyses of soil samples Analytical results of water samples from two separate vessels from M93 Analytical results of soil samples at British sites The surface features of the bronze fragments and the presence of corrosion products detected by XRD XRD results of corrosion products on bronze fragments from Tianma-Qucun Formulae of selected corrosion products and JCPDS numbers The relative molar volume of common corrosion products of bronzes Checklist of alloy type, microstructure, secondary metallic copper, sulphide, sulphate, black layer, and chloride in the Jin bronzes The composition of the Jin bronzes from the tomb of Jin state minister Zhao A summary of alloy type proportions and average composition for different periods and regions The compositions of Yinxu bronzes The composition of bronzes from an elite tomb at Xingan, Jiangxi The composition of bronzes from the Yuguo cemetry The composition of Yan bronzes from the Liulihe site The composition of bronzes from the tomb of Marquis Zeng (in Shouxian, Anhui) The composition of Chu bronzes from Xichuan The composition of Chu bronzes from Baoshan The composition of bronzes from Chu tombs on Zhaojiahu (in Dangyang, Hubei) The composition of Wu bronzes from Southern Jiangsu Proportions of general alloy types for bronzes through the Chinese Bronze Age The content of As and Fe for bronzes from different sites

vii

4 5

6

7 12 17 91 20 21 24 25 25 26 29 32 32 32 107 36 38 42 44 44 45 126 47 48 50 130 64 137 66 69 70 72 73 73 74 74 75

77 77

CHAPTER 1: INTRODUCTION

CHAPTER 1 INTRODUCTION The subject of this research project is the technical study of bronze fragments from the site of Tianma-Qucun. The site of Tianma-Qucun is in southwest Shanxi province, China. It dates to the periods of the W estem Zhou and the early Spring and Autumn, i.e. 1027-650 BC. This site was identified as the capital of the early Jin state. The state of Jin was one of the Western Zhou (ca. 1027-771 BC) vassal states and the most powerful state during the Spring and Autumn period (770-475 BC). This research is significant because: 1) Jin bronzes have rarely been studied in terms of metalworking technology, nor has there been a comparison of Jin bronzes from the elite tombs (i.e. tombs of the lords, minister, and their wives) and other class (i.e. unspecified, but does not include the lords, minister and their wives) tombs; and 2) it is a rare opportunity to study bronzes with provenance and environmental information. This study aims to provide new data on Jin bronzes, specifically on casting techniques and the deterioration of these bronzes in their burial environment. This study contributes data on archaeometallurgy in China, and helps understand Jin culture by comparing the bronzes for the elite class with that for other classes, and comparing bronzes of different periods. Corrosion study helps guide investigative cleaning and conservation treatment, and predicts the stability of these bronze objects from the Jin state. The site of Tianma-Qucun had been investigated by archaeologists from the Shanxi Provincial Institute of Archaeology and Peking University since the early 1960s (Department of Archaeology, Peking University & Shanxi Provincial Institute of Archaeology, 1992, 124-228). Many small tombs were excavated in the 1980s. The most significant discovery at this site was the cemetery of the W estem Zhou lords of Jin. The Jin cemetery was discovered during rescue excavations in 1992 to 1995. The discovery and excavation of this cemetery has been among the most important archaeological achievements of the last decade, and one of most important discoveries made so far in W estem Zhou archaeology. The discovery of this cemetery provides archaeological evidence for the location of the early Jin capital. Seventeen large tombs at the cemetery were completely excavated by 1995. These tombs were occupied by the lords of Jin and their wives (Department of Archaeology, Peking University & Shanxi Provincial Institute of Archaeology, 1995, 39). The state of Jin, one of the Zhou vassal states, was founded in the former Xia (legend) territory in the beginning years of W estem Zhou (ca. 1000 BC). It was the biggest of the Eastern Zhou states, which included the areas of modem southern Shanxi, southern Hebei and northern Henan. It lasted for about 600 years and broke up circa 450 BC into three smaller states, Zhao, Wei and Han ( Chang, 1977, 317). According to historical literature, the capital of the Jin state

was moved several times. The geographical locations of the Jin capitals Yi, Quwo, and Jiang are described in ancient texts, but the exact locations of them have not been substantiated by archaeology. In the 1950s the site of Houma was discovered. The site was identified as the last capital of Jin named Xintian from Duke Jing onward (585-403 BC). The main question which concerned archaeologists was: where was the capital of the early Jin state (1027-585 BC)? The recent discovery of the Jin cemetery at Tianma-Qucun in Quwo has now provided an answer to this question. The grave goods consist primarily of bronzes; jades, pottery and chariots were also present. The bronzes include ritual vessels, weapons, sets of bells, horse fittings and small ornaments. Bronzes show an extremely close morphological resemblance to bronzes from the centre of the Zhou kingdom in the Wei River valley of modem Shaanxi province (Xu Jay, 1996, 218). Inscriptions found on bronzes appear mainly on vessels and bells, revealing personal identities and historical information. Forty-seven bronze fragments from the elite and other tombs have been examined for this technical study. Both metal and corrosion products have been examined to reveal the casting techniques and the development of corrosion. Six soil samples from the tombs and two water samples from two vessels buried in tomb M93 were also analysed in this study. In contrast to most studies on ancient Chinese bronzes from unknown archaeological contexts, this study begins to incorporate the available excavation and environmental data. The study of corrosion aims at assigning differences in corrosion conditions to differences in the original metal. The inadequate soil samples do not allow me to build up a model for the connection of microenvironment and corrosion. However, the soil samples help understanding the formation of black passivating layers and redeposited copper. Furthermore, the results of the technical study should directly apply to investigative conservation cleaning so as to evaluate the original dimensions, and surface decoration of these bronze artefacts. This monograph is organised as follows: Chapter 2 is a general review of the Chinese Bronze Age, the history of the Jin state, and the tradition of Jin bronzes based on the available archaeological materials. Chapter 3 describes the site of Tianma-Qucun. It provides details on several tombs of the Jin lords. Chapter 4 provides the methodology of the project. Sample preparation and analytical methods used for the technical study are summarised in this chapter.

1

CHAPTER 1: INTRODUCTION The analytical results of metalworking technology of these bronze fragments from Tianma-Qucun are presented in Chapter 5. These results provide original data on Jin bronzes, including the source of raw materials and casting techniques. The analytical data of mould materials are also included. A comparison of the composition of the Jin bronzes with the "Six Formulae" is also carried out in this chapter. Chapter 6 presents the analytical results of corrosion on the bronze fragments. The corrosion conditions of those bronzes varied a lot among different tombs and even among different objects in one tomb. The questions raised are: Why are some of these bronzes much more corroded than others? What are the causes of corrosion: original materials and techniques or burial environment? Six soil samples and two water samples from the site were examined to help understanding the development of corrosion on the surface of the bronze objects. In contrast to most studies on corrosion of ancient bronzes that lack archaeological contexts and environmental parameters, this study attempted to build a better understanding of corrosion development of bronze in its burial environment. However, more detailed burial contexts and more environmental data are required. Conservation aspects are also discussed in this chapter. Chapter 7 compares the available data on alloy composition to examine the differences between Jin bronzes for elite class and other classes. Comparison of Jin bronzes and bronzes from other Chinese cultures is conducted by incorporating the published data into my study. Conclusions are presented in Chapter 8. The study provides a better understanding of metalworking technology of Jin bronzes and of the Jin culture; studies on corrosion of these bronzes help guides the preservation and conservation of the Jin bronzes. This chapter will also suggest key questions for further study. Technical data for the samples are reported in the catalogue on an attached CD.* Each sample is given a catalogue entry. In the texts, the number following a sample number refers to the figure in the relevant catalogue entry.

Please note that the CD referred to above has now been replaced with a download available at: www.barpublishing.com/additional-downloads.html

2

CHAPTER 2: THE CHINESE BRONZE AGE AND JIN BRONZES

CHAPTER2 THE CIDNESE BRONZE AGE AND JIN BRONZES This Chapter presents a general review of the Chinese Bronze Age, the history of the Jin state, and Jin bronzes found from the archaeological sites.

regions of China. The earliest bronze artefact yet known is a knife found from a Majiayao site in Gansu province, dated to about 3000 BC. Another bronze knife was found from a Machang site in Gansu province, dated to 2300-2000 BC (Gansu Museum, 1979, 141, 142, 151). Both Majiayao and Machang cultures were derived from the Y angshao culture, a Neolithic culture which originated in the central plains and lasted from 5000-2000 BC. Bronze fragments, slags and remains of smelting furnaces were found in several Longshan sites in the Central Plains, dated to 2400-1900 BC (Henan Archaeological Research Institute et al. 1983, 8-20; An Zhimin, 1981, 269-285). These remains are suspected to be the products of a later period and do not belong to the Longshan culture (An Zhimin, 1981, 285). This implied that smelting techniques of copper ores in the Central Plains might have begun earlier. Small brass objects were found in a Y angshao site in Shaanxi province and a Longshan site in Shandong province. Early copper objects were also found from other cultural sites in Gansu, Hebei province and Inner Mongolia Autonomous Region, including pure copper, CuSn, Cu-Sn-Pb and Cu-Pb alloys (Archaeometallurgy Group at Beijing University of Steel & Iron Technology, 1981, 287302).

2.1 THE CHINESE BRONZE AGE "The term 'Bronze Age' was first coined in the West by Christian Jurgensen Thomse (1788-1865), curator of the National Museum of Denmark. It was the second of the three ages representing a new classification of the collections in the museum: Stone, Bronze, and Iron Ages ...... 'The Age of Bronze' is the age 'in which weapons and cutting implements were made of copper or bronze." (Chang, 1980, 35). Gordon Childe (1944, 1) interpreted the three archaeological ages as "a series of consecutive stages in technological development, in the evolution of forces of production". Childe (1957, 1) defined 'The Bronze Age' as "a technological stage in which metal - actually copper more often than the alloy of copper and tin - first came to be used regularly for the principal cutting tools and weapons to replace or supplement the earlier equipment of stone, bone, and wood." These definitions stress bronze metallurgy as an industry geared around productive activities (Chang, 1980, 36).

Questions of concern to scholars were: When did the Chinese Bronze Age begin? How did the Bronze Age originate in China? It had been debated for a long time (before the discovery of Erlitou culture in the 1950s ) whether the knowledge of bronze in ancient China was taken from earlier bronze makers in the West or whether China developed its own bronze technology independently. Based on the fact that more and more archaeological materials of bronze casting have been found, there is now no doubt that the Chinese bronze culture was indigenous. Bronze technology of ancient China was strongly influenced by its ceramic technology rather than from foreign influence. The highly advanced pottery industry of the immediate pre-metal period formed the foundation of the bronze industry. The suitable clay mixture for crucible manufacture offered no problem for clay model preparation and the making of moulds. Temperatures sufficient to melt copper were attainable in the pottery kiln. The productive processes were similar between bronze casting and pottery industry, but bronze casting was more complicated than pottery manufacture.

K. C. Chang (1980, 35) pointed out "Since bronze was not widely used for agricultural implements, the Bronze Age of China was not achieved primarily through a revolution in productive technology. If there was a revolution, it was in the realm of social organisation." The Chinese Bronze Age refers to " the period in which bronzes had a significant presence in the archaeological record" (Chang, 1980, 35). Wu Hung (1995, 65) has reached three conclusions regarding the function of Chinese bronze: "First, Chinese bronze was primarily for non-productive purpose. These non-productive bronze objects fall into two large categories: (1) vessels and musical instruments used in rituals, and (2) weapons and chariot fittings. Some weapons and chariots could have been used in warfare...... Second, some bronze drills, knives, chisels and small spades have been found, but it would be dangerous to identify these as utilitarian tools in daily life. They could have been used for certain rituals...... Third, excavated Shang and W estem Zhou agriculture implements are made of stones."

The sophisticated ceramic technology in ancient China, especially the sinter techniques, including kiln structure, firing temperature and atmosphere (reducing conditions) formed the basis for furnaces and technology of metal smelting. The important character of bronze casting in ancient China was ''pottery casting", in other words, bronze casting developed out of ceramic technology.

Differing from the Copper Age of Near East and South America in which native copper was the earliest source of copper artefacts (Tylecote, 1992, 1), the beginning of the use of copper in China included varieties of native copper, bronze, leaded bronze and brass. This is due to the vast territory and extensive varieties of copper sources in different

3

CHAPTER 2: THE CHINESE BRONZE AGE AND JIN BRONZES

It is now originated and lasted BC). The vessels.

archaeological materials, particularly of ritual vessels, Chinese scholars divided the Bronze Age into different stages, with different kinds of periodisation being made by different scholars.

generally agreed that the Chinese Bronze Age independently in the Xia culture (ca. 2000 BC) for about 2000 years up to the Han dynasty (206 Chinese Bronze Age is characterised by ritual On the basis of historical literature and

Table 2.1 Periods of the Chinese Bronze Age and summary of characteristic bronze features (Ma Chengyuan, 1995, 417-457) Period Xia

Date ca. 1900-1600 BC

Early Shang

ca. 1600-1450 BC

Middle Shang

ca. 1450-1200 BC

Late Shang

ca. 1200-1027 BC

Early Western Zhou

ca. 1027-948 BC

Middle Western Zhou

947-876BC

Late Western Zhou

875-771BC

Early Spring and Autumn

770-650BC

Middle Spring and Autumn

650-550 BC

Late Spring and Autumn

550-476BC

Early Warring State

475-350 BC

Late Warring State

349-221 BC

Qin and Han dynasty

221BC-220 AD

Features Object types include weapons, tools, musical instruments and ritual vessels (jue). Decoration patterns were rare. Ritual vessels were much more advanced, including food, wine and water vessels. Casting techniques were simple, with most ritual vessels being tripods. Decoration began to be elaborate and dense, casting techniques were improved, lugs were not aligned directly over legs. Simple inscription such as clan symbol of casters appeared. New types of vessels appeared. Rectangular objects were abundant which indicated the improvement of casting techniques. Large objects were cast which implied the existence of well-organised political authority. Bronze inscriptions were simple and short, consisting of clan name of the owner or the name of the sacrificed person. Bronze arts were fundamentally the same as that of Late Shang except the changes in proportion of ritual vessel types. The inscription became lengthy and recorded the political events. The wine vessels decreased and the food vessels increased. Transformation period of bronze art. Vessel forms no longer strove for beauty, but were straightforward and ordinary in their features rather than unusual. Designs became more simplified. Most of the bronze inscriptions were about assignment and inheritance. The art of bronze casting began to decline, with being simple in both shape and decoration. Technological changes occurred in two ways: a mother model had been repeatedly used to cast identical works, and the details of the large vessels had been separately cast and then welded onto the main body. The bronze industry of this period was a continuation of that of Western Zhou in many ways, with minor changes. Bronze decoration was crude, bronze vessels with lengthy inscriptions were rare. Inscriptions usually consisted of the weddings of lords and their ministers, and the records of the casters. Bronze vessels used for ritual purpose decreased, but vessels for practical use increased. Interlocked patterns and overlapped patterns were popular. Animal patterns became realistic, although the deformed animal masks were still present. The Iron Age had started in China in this period. The bronze industry began to revive and reached its second peak, with the appearance of new features in casting techniques. Composite casting and welding and riveting methods were used in popularity. New techniques for casting together metals of different composition also appeared. Bronze arts were in many ways the same as the late Spring and Autumn period. The styles of bronze art varied between different states. The typical bronze decor of this period were themes from daily life rather than for spiritual ideals. The lost-wax technique came into regular use as late as the transition between the Spring and Autumn period and the Warring States period. Bronze art began to decline in this period due to the popularity in the use of iron objects. Bronze objects decreased, with large objects being rare, while small bronze objects such as swords, coins and seals being popular. Inlay techniques were advanced. Inlays were made of gold, silver, copper and turquoise. The Chinese Bronze Age ended in this period. The Han bronze industry focused on life style objects which were nearly without decorations and few inscriptions. The use of gold and silver for inlay was widespread. The casting of mirrors was common and its technique was extremely advanced in the Han dynasty.

4

CHAPTER 2: THE CHINESE BRONZE AGE AND JIN BRONZES

Ma Chengyuan, the former director of Shanghai Museum, divided the Bronze Age into thirteen phases according to the development of the bronze industry itself in terms of typology and decoration (Ma Chengyuan, 1995, 437). The dates and the features of those phases are summarised in Table 2.1.

techniques, piece moulds replaced single and bivalve moulds to produce large and complex objects. A large number of forms of bronze objects were made, including ritual vessels, weapons, tools and musical instruments. Bronze decor, especially animal masks were sophisticated. Inscribed bronzes increased and bronze vessels with lengthy inscriptions became popular in the Western Zhou period. Stage3: Prosperity, dates from the middle Western Zhou to the Warring States period, i.e. 947-221 BC. Bronze vessels became thin and light, and bronze decor became simplified. Both binary tin bronze and ternary leaded tin bronze were made in this stage. The Six Formulae of bronze composition in the Kao-gong-ji of Zhou-Ii originated in this period. In addition to the techniques of integral-casting and composite-casting, lost-wax, welding and riveting, inlay and gilt techniques emerged in this period.

In terms of technology, the development of bronze casting in ancient China was divided into the following stages by Tian Changhu (1987, 15-19):

Stage 1: Sprout, dates to the periods from the late Neolithic period to the early Shang dynasty, i.e. 1900-1450 BC. Tin bronze became predominant all over China. Single or bivalve moulds made of stone or clay were used for casting simple tools. Bronze decor was rarely used, however where it was used nipple patterns were almost the only design. Stage 2: Mature, dates from the middle Shang to the early Western Zhou, i.e. 1450-948 BC. Bronze manufacture in this stage was of large scale and advanced techniques. In terms of alloy composition, the ternary leaded tin bronze developed from the binary tin bronze. In terms of mould

A checklist (Table 2.2) of the Chinese Bronze Age can be made based on published materials (Tian Chenghu, 1987, 15-19; Ma Chengyuan, 1995, 417-457; Su Rongyu et al. 1995,2)

Table 2.2 Checklist of Chinese Bronze Age Phase

Object types

Decorations

Techniques

Composition

Xia Culture

weapons; tool; musical instrument; Jue and Jia ( drinking vessels) weapons; tool; whole set of ritual vessels

rare except nipple pattern

bivalve moulds

Cu Cu-Sn

animal mask: tiao tie geometric design simple inscriptions designs became simple, animal mask declined, curved and waved patterns appeared, lengthy inscription interlaced dragon and snake patterns were predominant, lengthy inscription was rare

bivalve moulds; piece-moulds; organic burnout In addition to Shang's, mother model and welding appeared

Cu;Pb; Sn; Cu-Sn; Cu-Pb; Cu-Pb-Sn Similar to Shang's

Cu inlay, lost wax, composite casting, welding, riveting, decor block and Six Formulae appeared

geometric patterns, themes from daily life

Inlay of Cu, Au, Ag; gilt

Similar to Shang's, but the proportion ofleaded bronzes increased Similar to the Spring and Autumn Period's

Shang Dynasty

Western Zhou Dynasty

food vessels increased, but wine vessels decreased

Spring & Autumn Period

similar to Western Zhou's, but vessels for daily use increased

Warring States Period

small objects increased

casting process of bronzes is described as follows. It can be illustrated in Figure 2.1.

The traditional casting technique of Chinese bronzes, piecemould casting, has been the interest of both Chinese and Western scholars (Archaeometallurgy Group at Beijing University of Steel and Iron Technology, 1978, 23-35; Hua Jueming, 1985, 481-501; Barnard, 1961, 1975; Chase, 1991; Meyers, 1986, 293-295) in recent decades. The piece-mould

1.

5

A model of clay representing the body of a vessel without its ornaments was made, and surface decorations were carved or impressed into the model, then the model was baked to dry.

CHAPTER 2: THE CHINESE BRONZE AGE AND JIN BRONZES

2.

3.

4.

5.

Moulds were made by pressing a flat piece of clay of a certain thickness against the model. The decorations were transferred from the model to the mould, and finer details, including inscriptions were added. The mould was finished and then baked to dry. The inner core was made by scraping down the surface of the model. The thickness of clay scraped away was equal to the wall of the bronze object to be cast. The air vents and pouring gate were produced. The moulds were assembled around the core and joined to the core with chaplets to prevent the casting space from shifting or closing during pouring so as to assure the precise shape of the object. The mould assembly was preheated and molten bronze was then poured into the moulds. The purpose of preheating was to prevent the molten bronze from sudden cooling on contact with the mould.

method, which appeared in the Late Shang dynasty. An example of a Late Shang object made by this technique was found as well. This technique is similar to the lost-wax technique, using rope instead of wax (pers. comm. Prof. Hua Jueming). In terms of the composition of bronzes, the "Six Formulae"

recorded in the Kao-gong-ji of Zhou-Ti are of particular interest and have been the subject of investigation. The "Six Formulae" describe the ratios of Cu to Sn for different types of objects. Two schools of interpretation, Liang Jin's and Dai Zhen's, are present due to the uncertain meaning of the word "~" in the texts. Liang Jin (1924, 1262) believed that"~" refers to bronze alloy, while Dai Zhen (1955, 39) believed that "~" refers to copper. In addition to these two schools of interpretation, Zhang Zigao (1958, 161) offered the third interpretation, in which the formula for mirrors and specula is different from the other two interpretations. The "Six Formulae" can be expressed in weight percentages (Table 2.3). Scientific analyses of bronzes often disagree with these formulae, which makes scholars question their value (Barnard, 1961, 12; Hua Jueming, 1985, 511; Su Rongyu et al. 1995, 273).

The lost-wax method appeared in China rather late, i.e. the transition between the W estem Zhou and the Spring and Autumn. However, a lot of exquisite Shang and Zhou bronze objects with complex decorations, but found before the appearance of the lost-wax method, made scholars wonder how they were made. Recent research by Tan Dalui et al. of the Shanghai Museum discovered a organic bum-out

Table 2.3 Three schools of interpretation of the ancient texts of the "Six Formulae C f::. 1f ) " Type ofobjects Zhong-bells & Ding-cauldrons C ~$ ) Axes & Hatchets C ~ fr ) Daggers-axes & Halberts( :l•••

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85

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