Scientific Study On Decorative Sheetmetal Artifacts Unearthed In The Region Of The Chu Culture Of The Eastern Zhou Period

The Chu Culture was one of the most influential regional cultures in the Eastern Zhou period.Especially,after the middle of the Spring and Autumn period,metal technology of Chu was highly developed and gradually seized the control of important mineral sources in the middle and lower Yangtze River Basin.The ancint tombs excavated at the Caojiagang(M5)and Zhaoxiang(M12)in Dangyang,Yichang,Hubei Province,and at GeLling in Xincai,Henan Province,are typical cemetery remains of the Chu State in the Eastern Zhou period.A large number of decorative sheetmetal objects were unearthed from these tombs.They are made of gold,bronze,tin and tin-lead alloy.These sheetmetal artifacts are exquisite and show a completely different technological style from that of casting bronzes of the pre-Qin period.This research conducts a sysmetic scientific investigation of these sheetmetal products,including chemical,metallographic and lead isotope analysis.Experiments simulating the ancient sheetmetal working have also been carried out.On the basis of these invesitigations,this thesis discusses the manufacturing technology of sheetmetal products in the Eastern Zhou period of the Chu Culture,their regional features,characteristics of their lead isotope ratios and other relevant issues.The observation results have revealed that these objects are all made up of base-sheets covered with foil.The metal sheets are slightly thicker and the composition analysis shows that there are two major types of alloy,lead-tin bronze and lead-tin alloy.There are a small number of pure tin products as well.The covered metal foils are usually decorated with delicate patterns,and the thickness can be as low as a few microns.The major materials are gold-silver alloy and pure tin.There are very few silver foils(all from the tomb of Geling)and tin-lead foils.The main combination forms of foil and base sheet are gold foil with bronze sheet and tin foil with tin-lead sheet,while gold foil with tin sheet,tin foil with tin sheet and tin-lead foil with tin-lead sheet also exist.According to the observation,all of these sheets and foils were made by forging.The examination of their metallographic microstructures confirms this.The decorative patterns on the surface of gold foil and tin foil are relatively complex,but they can be organized and classified into smaller line units or spots,and there are obvious marks of processing tools inside the lines and spots.Based on simulation experiment,we speculated that the production process of these decorative artifacts should be as follows:forging out foils and sheets,cutting into shapes,drawing decorative patterns,wrapping the foil onto sheet and punching holes,and at last tying them to the surface of other artifacts.The production process of those sheetmetals unearthed from the Geling tomb in Xincai,Henanis slightly different from those from the two tombs in Dangyang,Hubei.The lead isotope ratio analysis shows that the isotope ratio distribution of the tin and tin-lead alloy artifacts unearthed from Zhaoxiang M12 and Caojiagang M5 is different from the similiar artifacts from Geling.In addition,the characteristic is different from that of the bronze artifacts unearthed from other areas in the Eastern Zhou period.This indicates that there might have been some different mineral sources.This kind of artifacts are mainly used as chariot and horse ornaments and armour ornaments.Similar artifacts have also been found in other parts of ancient China,such as Qin Cultural area in the northwest,the northern steppe area and the Yue Cultural area in the southeast,etc.The combination of tin-lead alloy sheet and tin foil was rare in the pre-Qin period.The use of a large number of sheetmetal ornaments and all kinds of tin artifactsindicates that significant changes took place during the Eastern Zhou Period,as evidenced by the development of metal technology,various types of materials,diversity of technology and resources..This situation coincides with the diversified pattern of handicraft industry,the rapid development of economy and culture,and the great "revolution" of social changes in the Eastern Zhou period.