Tombac
Also: Red brass
Tombac is a copper-zinc alloy with a copper content of 67-90%, known as a decorative material and historical coin metal due to its gold-like colour.
Tombac (from Malay tembaga, copper) refers to a gold-coloured, glossy 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, inexpensive 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 basic character as a base metal with no precious metal content.
Uses
Tombac is used wherever a gold-like appearance is required 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 core or ring material.
- Jewellery and decorative items: Tombac imitates the appearance of yellow gold in the costume jewellery industry and in fittings.
- Engineering: Owing to its good cold formability and corrosion resistance, tombac is used in cartridge cases, watch cases and plumbing fittings.
Tombac and Precious Metal Valuation
Since tombac has no precious metal content, it is only relevant to the melt value calculator via the current copper price. Tombac objects - even gilded ones - have no intrinsic gold value; only the material value of the copper and zinc they contain matters.
Material value of tombac = Weight (g) x copper content x copper price (EUR/g)
Gilded tombac pieces are generally traded at purchase as base metal, provided the gold layer is less than 0.5 microns - the amount of gold is then negligible.
Distinction from Similar Alloys
- Nickel silver: copper-zinc-nickel, silver-coloured - contains no silver.
- Red gold: a genuine gold-copper alloy with a defined fineness (e.g. 750/1000 Au).
- Doublet / gold doublet: a mechanically bonded gold layer on base metal - a higher gold content than mere gold plating.
In Brief
Tombac is a high-quality gold imitation 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 and not the gold market.