Identifying recipes of historical cupels from Yunnan, China

Abstract

Cupellation was the most important silver extraction technology in the ancient world. No later than the Han Dynasty, China adopted cupellation in silver extraction. However, the cupel, the most significant physical evidence of this process, is not frequently identified archaeologically in China and is rarely analyzed to reconstruct the technology and material characteristics of the process. Here we present new findings from the sites of Beiyachang and Baixiangchang in Dali, Yunnan. Five used cupel fragments from the two sites were generally dated to the Ming and Qing Dynasties. Chemical and microscopic analyses show that the cupels were made primarily of a mixture of bone ash (∼30–50 wt %) and plant ash (∼50–70 wt %). Intriguingly, Chinese historical documents recorded only plant ash as the raw material of cupels and did not mention bone ash until the nineteenth century AD. Thus the current analytical result provides the first physical evidence of cupels made with a bone ash and plant ash mixture in historical China.