page_title: Huaca Rajada
section_title: Metalwork
hierarchical_section_title: Huaca Rajada / Metalwork
caption_attribution_description: English: Mask at the Tumbas Reales de Sipán Museum, Lambayeque, Peru. Español: Mascara en el museo del Señor de Sipan, Lambayeque, Peru.
context_page_description: Huaca Rajada, also known as Sipán, is a Moche archaeological site in northern Peru in the Lambayeque Valley, that is famous for the tomb of Lord of Sipán, excavated by Walter Alva and his wife Susana Meneses beginning in 1987. The city of Sipán is dated from 50–700 AD, the same time as the Moche Period.
context_section_description: During the excavations in 1987–1990, a spectacular treasure of gold and silver ornamental and ceremonial artifacts was recovered, dating to AD 50–300. These objects demonstrate the outstanding craftsmanship of the Moche metalsmiths through their use of elaborate and advanced metalworking techniques. Moche smiths made these artifacts out of thin sheets of copper alloys, using electrochemical processes to purify an extremely thin (0.5–2.0 μm) layers of gold or silver coating.
  To make the artifacts, copper ingots were hammered into sheet metal and formed into the desired shape (e.g. a mask). While the exact method for adding the gold film to the outside is not known, one well-accepted theory is that gold was likely dissolved in aqueous solutions of corrosive compounds recovered from the Northern Peruvian deserts and brought to a low boil, after which the copper sheet was dipped in resulting in the reaction:
  2Au³⁺ + 3Cu ⇌  2Au⁰ + 3Cu²⁺
  thereby dissolving copper and depositing gold on the surface of the metal. The sheet is then heated to between 500 and 800ₒC, allowing the gold film to permanently bond to the surface. These gold films were not pure gold, but have been found to be of gold-copper-silver solutions (ex. Cu₂₈Au₂Ag).
  Some of the silver artifacts (namely individually made head-shaped beads, about 4.0 cm by 5.1 cm) were formed by alternating between hammering and annealing copper-silver alloy (Cu₁₈Ag₁Au) resulting in copper-oxide forming along the surface which can be removed using an acid (plant juices) or base (stale urine that has turned to ammonia). After many repetitions, the copper will be depleted resulting in the appearance of pure silver (in actuality silver only makes up 18% of the surface). Other silver artifacts are believed to have been made in roughly the same manner, but contain as much as 90% silver on the surface 
  Examples of metalwork found in Sipán include the above-mentioned head-shaped beads, peanut-shaped beads, coffin straps, fan handles, spearheads, a copper-plated banner, ceremonial knives, golden headdresses, silver and gold nose and ear ornaments, scepters, a gold necklace made of 10 spiderweb beads (spider bodies with human faces sitting on golden wires), a gilded copper animal (possibly fox or dog), among others. The vast majority of these works were placed in richly decorated tombs, indicating both their high value toward the Sipán leadership and the frequent need for artisans to continue to make new artifacts as old ones were buried.
caption: Mask at the Tumbas Reales de Sipán Museum, Lambayeque, Peru
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