thumbnail|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, or tombak, is a brass alloy with high copper content and 5–20% zinc content.<!--The following is a commercial metal sales site, and not a reliable source for this type of academic metallurgical information:--> Tin, lead or arsenic may be added for colouration.

It is a cheap malleable alloy mainly used for medals, ornament, decoration and some munitions. <!--Out until quote is provided, and the fact is elsewhere substantiated, because conflicts with article content: "In older use,"-->The term may apply to brass alloy with higher zinc content.<!--Out until quote is provided, and the fact is elsewhere substantiated, because conflicts with article content: "as high as 28–35%".--><!--A commercial metal sales site, and not a reliable source for this type of academic mettalurgical information: He notes that the specific gravity of brass, in general, is "greater than the mean density of its constituents, varying from 7.82 to 8.73, according to the proportion of zinc and copper". a combination that would make it a tombac according to Ure.

Other tombac compositions that Ure reports are:

  • "Red tombac from Paris": copper 90.0%, zinc 7.9%, 1.6% lead; and
  • "Red tombac of Vienna": copper 97.8%, zinc 2.2%. and
  • "Mannheim gold (semilor)": 2.8 parts copper, 1.2 parts yellow brass, 0.3 parts tin.

Ure goes on to note that the alloy from which a form of "white metal buttons" are cast is composed of 3.2 parts yellow brass, 0.4 parts zinc, 0.2 parts tin.

With regard to modern forms, compositions include:

  • "CuZn15" (DIN, ISO): UNS, C23000; BS, CW 502L (CZ 102)—tombac with gold colour, good for cold forming, suitable for pressing, hammering, or embossing;
  • "CuZn12": a non-standardized tombac form, with same characteristics and applications as CuZn15, but of slightly different colour;
  • "CuZn10" (DIN, ISO): UNS, C22000; BS, CW 501L (CZ 101)–tombak with similar characteristics and applications as CuZn15 and CuZn12, but with a noticeable reddish colour.

Tempers

Typical tempers are soft annealed and rolled hard.

Applications

thumb|A "bronze" medal (actually tombac) from the [[1980 Summer Olympics]]

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Tombac is soft and easy to work by hand: hand tools can easily punch, cut, enamel, repousse, engrave, gild, 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 gold finish for and ornaments.

  • Most commonly, tombac in modern society is used in medals and awards of lesser importance, such as the German Oldenburg Long-Service Medallion for their Gendarmerie, and the Visit to Ireland Medal 1900 for the Irish police forces.
  • The and cuirass of the Imperial German and Prussian Army were at one time made of tombac.
  • German, particularly Prussian, field uniforms (which were also sold to equip the White Russians), had buttons and decorative fittings made of tombac.
  • Currently, tombac foils are used in arts and crafts for decorative articles, especially as an economic alternative to very expensive gold leaf.
  • Industry uses tombac foil for heating foils and etch applications.
  • Gilding metal is a type of tombac which is one of the most common jacketing materials for full metal and hollow-point jacketed bullets.
  • The 1980 Olympic 'Bronze' medals were actually tombac.
  • During World War II, the Royal Canadian Mint produced 5-cent pieces (nickels) in tombac in 1942 and 1943.
  • The German military used it for some combat medals during World War II.
  • The Swedish Armed Forces adopted a special-service round for the Carl Gustav m/45 submachine gun with a tombac-plated steel jacket surrounding the lead core of the bullet loaded in the cartridge. While the lands of the barrel can cut into the tombac, the steel jacket resists deformation and thus causes the gas pressure to rise higher than the previous soft-jacketed m/39, giving the bullet a muzzle velocity of .
  • Brass alloys, including tombak, are occasionally used in architecture, such as ornaments, roofs or outside wall plating. It withstands corrosion well.

See also

References

  • National Pollutant Inventory - Copper and compounds fact sheet
  • Tombac - DiracDelta Science & Engineering Encyclopedia
  • The Line Pickelhaube (Detailed explanation of Pickelhaube and use of Tombak for economic reasons)
  • Schlenk German tombak manufacturer: [http://www.schlenk.de]

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