Tin‐Rich Surface Decoration of Chinese Bronzes: A Case Study of the British Museum Collection

In this paper six bronze artefacts of the Eastern Zhou period to Han dynasty (770 BC ‐ 220 AD) with tin‐rich surface decoration in the British Museum collection were studied using a variety of analytical techniques. The decoration patterns include trellis patterns (菱形纹) on two swords of the Yue state, tiger's striped patterns (hu‐ban‐wen, 虎斑纹) on two swords from the Ba‐Shu region, a hexagonal star pattern (六角星纹) on a spearhead of the Wu state, and a cloud‐like pattern on a garment hook. The tin‐rich decorations on those objects were produced by deliberate tinning processes; at least three different tinning techniques were used, including the use of tin‐rich pastes for the trellis pattern of a Yue state sword and for the mottling decoration on the Ba‐Shu swords, amalgam tinning for the hexagonal star pattern on the spearhead of the Yue state, and hot tinning for the cloud‐like pattern of the garment hook. Different tinning techniques could have been applied to produce similar tin‐rich decoration patterns, and vice versa, a single tinning technique could have been used to produce different tin‐rich patterns on different objects.     

Contact tinning: A millennia‐old plating technology

Tinning copper and copper alloy objects by putting them into (electrical) contact with metallic tin in a boiling aqueous solution of potassium hydrogen tartar is a very old technique, but is nowadays almost forgotten. It was possibly invented by the Gauls and used intensively until the 20th century. This paper first briefly recounts the history of this galvanic process. To understand better the parameters influencing the thickness of the coat and thus to reconstruct this ancient technique, laboratory tests were undertaken by varying a series of parameters. The results are then presented with a short interpretation.