Tombac
Also: Red brass
Tombac is a copper-zinc alloy with a copper content of 67–90%, known for its gold-like colour as a decorative material and historic coin metal.
Tombac (from Malay tembaga, copper) denotes a gold-coloured, lustrous copper-zinc alloy with a copper content of between 67 and 90 percent by weight. The higher the copper content, the more reddish and gold-like the material appears – an effect that has made tombac an attractive low-cost substitute for gold for centuries.
Composition and Variants
| Designation | Cu content | Zn content | Colour |
|---|---|---|---|
| Red tombac | 85–90 % | 10–15 % | copper-gold |
| Yellow tombac | 72–80 % | 20–28 % | brass-gold |
| White tombac (prince's metal) | 67–72 % | 28–33 % | pale gold |
Small additions of lead, arsenic, or tin can influence the composition and workability, but do not change the fundamental character as a base metal with no precious metal content.
Uses
Tombac is used wherever a gold-like appearance is desired without paying the price of a precious metal:
- Coins and medals: Many circulation coins, orders, and decorations are made of tombac, sometimes with a thin gold plating (gold plating). Modern bimetallic coins also use tombac as a core or ring material.
- Jewellery and decorative items: Tombac imitates the appearance of yellow gold in the fashion jewellery industry and in fittings.
- Technology: Thanks to good cold-forming properties and corrosion resistance, tombac is used in cartridge cases, watch cases, and sanitary fittings.
Tombac and Precious Metal Valuation
Since tombac contains no precious metal, it is relevant to the melt value calculator only through the current copper price. Objects made of tombac – even gilded ones – have no intrinsic gold value; what counts is solely the material value of the copper and zinc contained.
Material value of tombac ≈ weight (g) × copper share × copper price ($/g)
Gilded tombac pieces are generally traded as base metal when bought, provided the gold coating is less than 0.5 µm thick – the quantity of gold is then negligible.
Distinction from Similar Alloys
- Nickel silver: Copper-zinc-nickel, silver-coloured – no silver content.
- Red gold: A genuine gold-copper alloy with a defined fineness (e.g. 750/1000 Au).
- Gold-filled / double: Mechanically clad gold layer on base metal – higher gold content than mere gilding.
In Brief
Tombac is a high-quality gold imitant with no precious metal content whatsoever – visually convincing, but materially worth only as much as the copper it contains. Anyone wishing to value tombac objects should refer to the current copper price rather than the gold market.