View source for Chemistry:Tumbaga

{{Short description|Non-specific alloy of gold and copper used in  pre-Columbian Mesoamerica}}
{{italics title}}
[[File:Tumbaga Pectoral, Quimbaya culture.jpg|thumb|right|250px|A ''tumbaga'' [[Engineering:Gorget|pectoral]] girdle of the Quimbaya culture; 300–1600 AD]]
'''''Tumbaga''''' is the name for a non-specific [[Chemistry:Alloy|alloy]] of [[Chemistry:Gold|gold]] and [[Chemistry:Copper|copper]] given by Spanish Conquistadors to metals composed of these elements found in widespread use in pre-Columbian [[Place:Mesoamerica|Mesoamerica]] in North America and [[Earth:South America|South America]].

The term is a borrowing from [[Social:Tagalog language|Tagalog]] ''tumbaga'' which in turn came from [[Social:Malay language|Malay]] {{lang|ms|tembaga}}, meaning '[[Chemistry:Copper|copper]]' or '[[Chemistry:Brass|brass]]'.<ref>{{Citation |title=tumbaga |date=2022-07-27 |url=https://en.wiktionary.org/w/index.php?title=tumbaga&oldid=68477687 |work=Wiktionary |language=en |access-date=2023-01-06}}</ref> It has also been spelled ''tumbago'' in literature.<ref>{{cite journal |last1=Fester |first1=G. A. |title=Copper and Copper Alloys in Ancient Argentina |journal=Chymia |date=1962 |volume=8 |pages=21–31 |jstor=27757215 |doi=10.2307/27757215 }}</ref>

==Composition and properties==
Tumbaga is an alloy composed mostly of gold and copper. It has a significantly lower [[Physics:Melting point|melting point]] than [[Chemistry:Gold|gold]] or [[Chemistry:Copper|copper]] alone. It is harder than [[Chemistry:Copper|copper]], but maintains malleability after being pounded.

Tumbaga can be treated with a simple [[Chemistry:Acid|acid]], like [[Chemistry:Citric acid|citric acid]], to dissolve copper off the surface. What remains is a shiny layer of nearly pure gold on top of a harder, more durable copper-gold alloy sheet. This process is referred to as [[Engineering:Depletion gilding|depletion gilding]].

==Use and function==
Tumbaga was widely used by the pre-Columbian cultures of South and Central America to make religious objects. Like most gold alloys, tumbaga was versatile and could be cast, drawn, hammered, gilded, soldered, welded, plated, hardened, annealed, polished, engraved, embossed, and inlaid.

The proportion of [[Chemistry:Gold|gold]] to [[Chemistry:Copper|copper]] in artifacts varies widely; items have been found with as much as 97% [[Chemistry:Gold|gold]] while others instead contain 97% [[Chemistry:Copper|copper]]. Some tumbaga has also been found to be composed of metals besides gold and copper, up to 18% of the total mass of the tumbaga.{{Citation needed|reason=These are important numbers, and we need to know their origin to check their veracity.|date=December 2023}}

Tumbaga objects were often made using a combination of the [[Engineering:Lost-wax casting|lost wax technique]] and depletion gilding. An alloy of varying proportions of copper, silver, and gold (typically in a percentage ratio of 80:15:5) was cast. After removal it was burned, turning surface copper into copper oxide, which was then mechanically removed{{clarify|Why wasn't a simple acid like those specified above used?|date=March 2017}} The object was then placed in an oxidizing solution likely composed of sodium chloride (salt) and ferric sulfate. This dissolved the silver from the surface, leaving only gold. When viewed through a microscope, voids appear where the copper and silver had been.

==The "Tumbaga" Wreck==

In 1992, approximately 200 silver "tumbaga" bars were recovered in wreckage off Grand Bahama Island. They were composed mainly of silver, copper, and gold plundered by the Spaniards during the conquests of Cortés and hastily melted into bars of tumbaga for transport across the Atlantic. Such bars were typically melted back into their constituent metals in Spain.<ref>{{cite book |title=The "Tumbaga" Saga: Treasure of the Conquistadors |date=2010 |publisher=Daniel Frank Sedwick |isbn=978-0982081822}}</ref>

==See also==
*{{annotated link|Chemistry:Guanín}}
*{{annotated link|Chemistry:Tombac}}
*{{annotated link|Chemistry:Orichalcum}}

==References==
{{reflist}}

==External links==
* [http://www.sedwickcoins.com/shipwreck_histories/tumbaga.htm Shipwreck recovered right after the conquest of Cortés with tumbaga gold bars]
* [http://www.sedwickcoins.com/tumbaga.htm The "Tumbaga" Saga: Treasure of the Conquistadors. Book about Tumbaga Bars]
*[http://libmma.contentdm.oclc.org/cdm/compoundobject/collection/p15324coll10/id/119785/rec/1 The Art of Precolumbian Gold: The Jan Mitchell Collection], an exhibition catalog from The Metropolitan Museum of Art (fully available online as PDF), which contains material on Tumbaga

{{Jewellery}}

[[Category:Copper alloys]]
[[Category:Gold]]
[[Category:Precious metal alloys]]

{{Sourceattribution|Tumbaga}}