Bronze Production Systems in 6-7 Centuries South Korea: Micro-Structural and Micro-Chemical Analysis of Slags

Abstract

Metallurgical remains such as crucible, mould, slag and tuyere are generated in the production of bronze. The analysis of slag in particular can be used to identify the raw materials, processes and environments (temperature and condition) employed in the bronze fabrication . The Gwanbuk-ri site in Buyeo is known as the location of a royal palace during the Baekje period, in the 6-7th centuries, and crucible fragments and slags used to make bronze were excavated there. The purpose of this study is to understand the process of bronze production and the origin of the raw ores used in the Baekje period, through micro-structure and microchemical analyses. Using chemical analysis and observation of the microstructure of the crucible and slag samples, we identified evidence of the bronze alloying and melting conditions. The melting process would have taken place under a variable redox atmosphere at 1,100 oC. Cu-Sn-Pb ternary bronze might have been produced by alloying Cu-Sn metal with lead ore (galena) in the Baekje period. The lead isotope composition ratios of 2 bronze slags were located in zone 2 and zone 3 of the lead isotope map in the southern Korean peninsula, which indicates the use of galena from south Chungcheong and north Gyeongsan provinces. For efficiency and cost-effectiveness, a concentrate of lead ore might have been transported from the mine to the consumer site.