The treasure of gold and silver artifacts from the Royal Tombs of Sipán, Peru — a study on the Moche metalworking techniques

In 1987–1990, a spectacular treasure of gold and silver ornamental and ceremonial artifacts was recovered scientifically from the unlooted Royal Tombs of Sipán, Peru (dated to approximately AD 50–300). These objects give evidence of the outstanding craftsmanship of the Moche metalsmiths and reflect the various elaborate metalworking techniques available at that time. The present paper summarizes the results of a study on an array of artifacts stemming mainly from the tomb of the “Lord of Sipán.” Most of the objects were found to be made of thin sheet metal (1–<0.1 mm thick), which was further worked by cutting, embossing, punching, and chasing. Three-dimensional structures were created from pieces of the sheet metal by mechanical or metallurgical joining (soldering or welding). The Moche metalsmiths were masters in making objects that looked like pure gold or silver. In the case of copper objects, the surfaces were often found to be gilded electrochemically by the deposition of very thin gold films. In the case of objects made of alloys of copper with gold and some silver (tumbaga) or of copper with silver, the surface gilding or silvering was achieved by the depletion of copper, mostly by selectively oxidizing the surface copper and etching away the copper oxides that are formed.