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 coinage metal.
Tombac (from Malay tembaga, copper) refers to 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 attractive as an inexpensive gold substitute 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 affect the composition and workability, but do not change the basic character as a base metal with no precious-metal content.
Uses
Tombac is used where a gold-like appearance is wanted without paying the price of precious metal:
- Coins and medals: Many circulation coins, orders and decorations are made of tombac, sometimes with thin gold plating. Modern bimetallic coins also use tombac as core or ring material.
- Jewellery and decorative items: Tombac imitates a yellow-gold look in the costume-jewellery industry and in fittings.
- Engineering: Thanks to good cold formability and corrosion resistance, tombac is used in cartridge cases, watch cases and sanitary fittings.
Tombac and precious-metal valuation
Because tombac has no precious-metal content, it is relevant to the melt value calculator only via the current copper price. Tombac objects — even gold-plated ones — have no intrinsic gold value; what counts is solely the material value of the copper and zinc they contain.
Tombac material value ≈ weight (g) × copper content × copper price (£/g)
Gold-plated tombac pieces are generally traded as base metal on purchase, provided the gold layer is less than 0.5 µm — 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).
- Rolled gold / gold doublé: a mechanically clad gold layer over base metal — a higher gold content than mere 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 look to the current copper price, not the gold market.