An Examination of Bronze Vessel Technology in the Unified Silla Period: Case Study on the Bronzes Excavated from Gwanbuk-ri Site in Buyeo

Archaeological excavations in Buyeo had revealed Bronze vessels interred within a hole in the building at the Gwanbuk-ri site. These bronze vessels are dated to the Unified silla period (9-10th centuries). To identify the bronze vessels’ manufacturing technology, metallurgical analyses were carried out using Optical Microscopy, SEM-EDS and EPMA. The results allowed a reconstruction of the manufacturing process of bronze vessels in the Unified silla. It proved that bronze vessels were manufactured with Cu-Sn alloy with varying tin contents, which may be related to the application of uncontrolled procedures in making the bronze alloys. Also a casting process was used to shape the bronze vessels and the strength and hardness of the container were improved through a quenching process. Twins were observed in one of the samples, so it was assumed that hot working had been attempted. Non-metallic inclusions in bronze vessels have circular or polygonal shapes, and Cu and S were detected. The presence of Cu-S inclusions showed the probable use of copper sulphide ores for metal production and smelting. Se and Te in the inclusions of the bronze vessels show that the copper ore is different. From the results of metallurgical analyses of bronze vessels excavated from other regions of the same era, casting and quenching treatments were confirmed, and the sequential relationship of the technological system was revealed.