Tombac

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Not to be confused with Tonbak. ‹See Tfd›
Ottoman tombac ewer and basin set - 1870 - Collection of Turkish and Islamic Arts Museum - Brought to museum in 1926 from the tomb of Sultana Pertevniyal.

Tombac, as it is 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]

Etymology[edit]

The term tombak is derived from tembaga, an Indonesian/Malay word of Javanese origin meaning copper.[citation needed] 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.

Common Types[edit]

  • Modern CuZn15

(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.

  • modern CuZn12

(not standardized) Same characteristics and applications as CuZn15; slightly different colour.

  • modern CuZn10

(DIN: CuZn10 ; UNS: C22000 ; BS: CW 501L (CZ 101) ; ISO: CuZn10) Similar characteristics and applications as CuZn15 und CuZn12; noticeable reddish colour.

  • modern White Tombak

CuZn10- that is Zinc content 10%, with trace arsenic

  • modern Enamel Tombak or Emailler Tombak

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]

    • "Gilting Tombak":
      • Copper 82%, Zinc 18%, Lead 1.5%, Tin 3%
      • Copper 82%, Zinc 18%, Lead 3%, Tin 1%
      • Copper 82%, Zinc 18%, Lead, Tin 0.2%

Copper 80%, Zinc 17%, 3% Tin

    • "Yellow Tombak of Paris" for gilt ornaments:

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]

Tempers[edit]

Typical tempers are soft annealed and rolled hard.

Applications[edit]

A "bronze" medal (actually tombac) from the 1980 Summer Olympics

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 objects d'art and ornaments.

See also[edit]

References[edit]

  1. ^ a b http://www.market-metal.com/reviews/reviews_175
  2. ^ Institute of Metals, Journal of the Institute of Metals Volume 43, Institute of Metals: 1930
  3. ^ http://www.schlenk.de/index.php?id=519&L=1&kat=1.1.1#719
  4. ^ Tibor Eric Robert Singer, German-English dictionary of metallurgy: with related material on ores, mining and minerals, crystallography, welding, metal-working, tools, metal products, and metal chemistry, McGraw-Hill: 1945: 298 pages
  5. ^ Andrew Ure, A dictionary of arts, manufactures and mines: containing a clear exposition of their principles and practice Robert Hunt (ed.), D. Appleton & Co.: 1856: pp243
  6. ^ a b Aaron Snowden Piggot, The chemistry and metallurgy of copper, Lindsay and Blakiston: 1858: 388 pages: pp354, google book reference: [1]

External links[edit]