Tumbaga is the name for a non-specific alloy of gold and copper given by Spanish Conquistadors to metals composed of these elements found in widespread use in pre-Columbian Mesoamerica in North America and South America.
The term is a borrowing from Tagalog tumbaga which in turn came from Malay tembaga, meaning 'copper' or 'brass'. [1] It has also been spelled tumbago in literature. [2]
Tumbaga is an alloy composed mostly of gold and copper. It has a significantly lower melting point than gold or copper alone [ citation needed ]. It is harder than copper, but maintains malleability after being pounded.
Tumbaga can be treated with a simple acid, like 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 depletion gilding.
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 gold to copper in artifacts varies widely; items have been found with as much as 97% gold while others instead contain 97% 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 ]
Tumbaga objects were often made using a combination of the 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. It was burned after removal, turning surface copper into copper oxide, which was then mechanically removed.[ clarification needed ] 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.
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. [3]
Solder is a fusible metal alloy used to create a permanent bond between metal workpieces. Solder is melted in order to wet the parts of the joint, where it adheres to and connects the pieces after cooling. Metals or alloys suitable for use as solder should have a lower melting point than the pieces to be joined. The solder should also be resistant to oxidative and corrosive effects that would degrade the joint over time. Solder used in making electrical connections also needs to have favorable electrical characteristics.
Brazing is a metal-joining process in which two or more metal items are joined by melting and flowing a filler metal into the joint, with the filler metal having a lower melting point than the adjoining metal.
Gilding is a decorative technique for applying a very thin coating of gold over solid surfaces such as metal, wood, porcelain, or stone. A gilded object is also described as "gilt". Where metal is gilded, the metal below was traditionally silver in the West, to make silver-gilt objects, but gilt-bronze is commonly used in China, and also called ormolu if it is Western. Methods of gilding include hand application and gluing, typically of gold leaf, chemical gilding, and electroplating, the last also called gold plating. Parcel-gilt objects are only gilded over part of their surfaces. This may mean that all of the inside, and none of the outside, of a chalice or similar vessel is gilded, or that patterns or images are made up by using a combination of gilt and ungilted areas.
Shakudō (赤銅) is a Japanese billon of gold and copper, one of the irogane class of colored metals, which can be treated to develop a black, or sometimes indigo, patina, resembling lacquer. Unpatinated shakudō visually resembles bronze; the dark color is induced by the niiro artificial patination process, involving boiling in a solution, generally including rokushō.
Plating is a finishing process in which a metal is deposited on a surface. Plating has been done for hundreds of years; it is also critical for modern technology. Plating is used to decorate objects, for corrosion inhibition, to improve solderability, to harden, to improve wearability, to reduce friction, to improve paint adhesion, to alter conductivity, to improve IR reflectivity, for radiation shielding, and for other purposes. Jewelry typically uses plating to give a silver or gold finish.
Gold plating is a method of depositing a thin layer of gold onto the surface of another metal, most often copper or silver, by chemical or electrochemical plating. Plating refers to modern coating methods, such as the ones used in the electronics industry, whereas gilding is the decorative covering of an object with gold, which typically involve more traditional methods and much larger objects.
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.
Shibuichi (四分一) is a historically Japanese copper alloy, a member of the irogane class, which is patinated into a range of subtle greys and muted shades of blue, green, and brown, through the use of niiro processes, involving the rokushō compound.
Guanín is an alloy of copper, gold and silver, similar to red gold, used in pre-Columbian central America. The name guanín is taken from the language of the Taíno people, who prized it for its reddish color, brilliant shine, and unique smell, and associated it with both worldly and supernatural power. It was also known as taguagua, and in South America as tumbaga. The Spanish referred to it as "low gold", distinguishing it from items made with a higher purity of gold.
The emergence of metallurgy in pre-Columbian Mesoamerica occurred relatively late in the region's history, with distinctive works of metal apparent in West Mexico by roughly 800 CE, and perhaps as early as 600 CE. Metallurgical techniques likely diffused northward from regions in Central or South America via maritime trade routes; recipients of these metallurgical technologies apparently exploited a wide range of material, including alloys of copper-silver, copper-arsenic, copper-tin and copper-arsenic-tin.
Panchaloha, also called Pañcadhātu, is a term for traditional five-metal alloys of sacred significance, used for making Hindu temple murti and jewelry.
Corinthian bronze, also named Corinthian brass or aes Corinthiacum, was a highly valuable metal alloy in classical antiquity. It is thought to be an alloy of copper with gold or silver, although it has also been contended that it was simply a very high grade of bronze, or a kind of bronze that was manufactured in Corinth. It is referred to in various ancient texts, but no certain examples of Corinthian bronze exist today. However, it has been increasingly suggested that a number of artefacts previously described as niello in fact use a technique of patinated metal that may be the same as Corinthian bronze and is similar to the Japanese Shakudō.
In metallurgy, refining consists of purifying an impure metal. It is to be distinguished from other processes such as smelting and calcining in that those two involve a chemical change to the raw material, whereas in refining, the final material is usually identical chemically to the original one, only it is purer. The processes used are of many types, including pyrometallurgical and hydrometallurgical techniques.
Depletion gilding is a method for producing a layer of nearly pure gold on an object made of gold alloy by removing the other metals from its surface. It is sometimes referred to as a "surface enrichment" process.
The Quimbaya (/kɪmbaɪa/) were a small indigenous group in present-day Colombia noted for their gold work characterized by technical accuracy and detailed designs. The majority of the gold work is made in tumbaga alloy, with 30% copper, which colours the pieces.
Colored gold is the name given to any gold that has been treated using techniques to change its natural color. Pure gold is slightly reddish yellow in color, but colored gold can come in a variety of different colors by alloying it with different elements.
Metallurgy in pre-Columbian America is the extraction, purification and alloying of metals and metal crafting by Indigenous peoples of the Americas prior to European contact in the late 15th century. Indigenous Americans had been using native metals from ancient times, with recent finds of gold artifacts in the Andean region dated to 2155–1936 BCE, and North American copper finds being dated to approximately 5000 BCE. The metal would have been found in nature without the need for smelting, and shaped into the desired form using hot and cold hammering without chemical alteration or alloying. To date "no one has found evidence that points to the use of melting, smelting and casting in prehistoric eastern North America."
Gold parting is the separating of gold from silver. Gold and silver are often extracted from the same ores and are chemically similar and therefore difficult to separate. The alloy of gold and silver is called electrum.
The Muisca raft, sometimes referred to as the Golden Raft of El Dorado, is a pre-Columbian votive piece created by the Muisca, an indigenous people of Colombia in the Eastern Ranges of the Colombian Andes. The piece probably refers to the gold offering ceremony described in the legend of El Dorado, which occasionally took place at Lake Guatavita. In this ritual, the new chief (zipa), who was aboard a raft and covered with gold dust, tossed gold objects into the lake as offerings to the gods, before immersing himself into the lake. The figure was created between 1295 and 1410 AD by lost-wax casting in an alloy of gold with silver and copper. The raft was part of an offering that was placed in a cave in the municipality of Pasca. Since its discovery in 1969, the Muisca raft has become a national emblem for Colombia and has been depicted on postage stamps. The piece is exhibited at the Gold Museum in Bogotá.
The Veraguas culture, also known as the Chiriqui culture, was a pre-Columbian Panamian culture. It is noted for the quality of its goldwork.