tombac

Tombac (rare French spelling) 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

The term tombak derives from the Javanese derived Indonesian (erroneously termed Malay) word tembaga- 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 or Malay loan words used in English, German or Dutch.

Common Types

• 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%

• • "French Tombak for sword handles", pommelsand fittings:

Copper 80%, Zinc 17%, 3% Tin

• • "Yellow Tombak of Paris" for gilt ornaments:

Copper 85%, Zinc 15%, trace% Tin

• • "Hanover Tombak":

Copper 85.3%, Zinc 14.7%

• • Chrysochalk

Copper 86%, Zinc 14%

• • "Red Tombak of Paris"

Copper 90%, Zinc 7.9%, 1.5% Lead

• • "Red Tombak of Vienna"

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

Typical tempers are soft annealed and rolled hard.

Applications

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.

• most commonly Tombak in modern society is used in medals and awards of lesser importance, such as the Dutch Oldensburge Long-Service Medallion for their Gendarmerie (Oldenburgse Onderscheiding voor Langdurige Dienst in de Gendarmerie).[[Wikipedia
• the Pickelhaube and cuirass of the Imperial German and Prussian Army were at one time made of tombak
• German, particularly Prussian field uniforms (which were also sold to equip the White Russians had buttons and decorative fittings made of tombak

• currently tombak foils used in art and craft for decorative articles, especially as an economic alternative to very expensive gold leaf.
• Industry uses tombak foil for heating foils and etch applications.
• armaments in the form of ballistic projectiles at Barnaul Machine Tool-Plant Zavod, in Russia, where Tombakis bonded via heat process with steel to produce a bi-metallic projectile, which combines the favourable qualities of steel and copper.
• The 1980 Olympic 'Bronze' Medals were actually Tombak
• During World War II Canada minted Canadian nickels
• German military use for some combat medals, during World War II.

See also

• Brass
• tumbaga

References

External links

• National Pollutant Inventory - Copper and compounds fact sheet
• Tombac - DiracDelta Science & Engineering Encyclopedia
• Detailed explanation of Pickelhaube and use of Tombak for economic reasons: [2]
• Schlenk German tombak manufacturer: [3]