Tumbaga and depletion gilding: copper-gold alloy with a gold skin (Colombia, Panama, Costa Rica, the Andes; about 100–700 CE onward)
Record: the document says itPattern: documents line upLens: our readingOpen: not yet proven
Year: 1992 · Places: Central America, South America, Europe
SUMMARYTumbaga and depletion gilding: copper-gold alloy with a gold skin (Colombia, Panama, Costa Rica, the Andes; about 100–700 CE onward) [Connections: Tech of the Americas, Nov 5, 2026]
RECORDWikipedia: "Tumbaga is an alloy composed mostly of gold and copper," and "Tumbaga can be treated with a carboxylic acid, such as oxalic acid, to dissolve copper off the surface" (depletion gilding). "By c. 100–700 CE, depletion gilding was developed by the Nahuange culture of Colombia." In Panama and Costa Rica, "Gold, copper and tumbaga objects started being produced" by 300–500 CE. "Tumbaga" was "the name given by Spanish Conquistadors for a non-specific alloy of gold and copper." About 200 silver tumbaga bars were recovered in 1992 from a wreck off Grand Bahama (Sedwick 2010)
PATTERNAlloying plus surface chemistry gave a gold look from a mostly copper object. The Spanish name for the alloy is a colonial label, not the makers' word
LENS (WW9)Copper again at the center: the copper people made gold out of copper's surface
OPENThe makers' own names for the alloy and the method. Which acids were used (plant juices are often said; not confirmed on the fetched pages)
SOURCEWikipedia, "Tumbaga"; Wikipedia, "Metallurgy in pre-Columbian America".