Tombac, as spelled in French, or Tombak is a brass alloy with high copper content and 5-20% zinc content.[1] Tin, lead or arsenic may be added for colouration.[2][3] It is a cheap malleable alloy mainly used for medals, ornament, decoration and some munitions. In older use, the term may apply to brass alloy with a zinc content as high as 28%-35%.[1][4]
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The term tombak is derived from tembaga, an Indonesian (erroneously termed Malay) word of Javanese origin meaning copper. Tembaga entered Dutch usage concurrent with their colonisation of Indonesia (see Dutch East Indies). Likely, the term was used generically to describe Indonesian high-copper brass items, including gamelan gongs. It is one of the very few Indonesian loan words used in English, German or Dutch.
(DIN: CuZn15 ; UNS: C23000 ; BS: CW 502L (CZ 102) ; ISO: CuZn15) Tombak with a gold colour, very good for cold forming, suitable for pressing, hammering, embossing.
(not standardized) Same characteristics and applications as CuZn15; slightly different colour.
(DIN: CuZn10 ; UNS: C22000 ; BS: CW 501L (CZ 101) ; ISO: CuZn10) Similar characteristics and applications as CuZn15 und CuZn12; noticeable reddish colour.
CuZn10- that is Zinc content 10%, with trace arsenic
An alloy of 95% copper and 5% zinc is very suitable for enamelling, therefore the name.
Ure notes the following forms of Tombak in widespread use during the time the text was published (1856)[5]:
Copper 80%, Zinc 17%, 3% Tin
Copper 85%, Zinc 15%, trace% Tin
Copper 85.3%, Zinc 14.7%
Copper 86%, Zinc 14%
Copper 90%, Zinc 7.9%, 1.5% Lead
Copper 97.8%, Zinc 2.2%
Piggot states the brass used for machinery and locomotives in England was composed of Copper 74.5%, Zinc 25%and Lead 0.5%- which would make it a tombak according to Ure.[6] Piggot's own definition of tombak is problematic at best: "red brass or tombak as it is called by some, has a great preponderance of copper, from 5 ounces of zinc down to 1/2 ounce of zinc to the pound [sic: copper?]"[6]
Typical tempers are soft annealed and rolled hard.
Tombak is easy and soft to work by hand: hand tools can easily punch, cut, enamel, repousse, engrave, gilt or etch it. It has a higher sheen than most brasses or copper, and does not easily tarnish. Historically it was used by the Javanese as a faux gold finish for objet d'art and ornaments.