Alloying Metal
Also: Additive metal, Master metal, Alloying element
An alloying metal is a base or precious metal added to a precious metal in a defined proportion in order to deliberately change its hardness, colour, melting behaviour or other properties.
An alloying metal (sometimes called an additive metal or master metal) is the portion of a precious-metal alloy that is not the precious metal itself. Without alloying metals, many everyday applications would barely be feasible: pure gold (999.9) is so soft that a fingernail can scratch it. Only when other metals are blended in does a piece of jewellery or a coin acquire the working hardness it needs. The fineness always tells you how much precious metal — and therefore how little alloying metal — a given alloy contains.
Which metals are used?
| Alloying metal | Typical use | Effect |
|---|---|---|
| Copper | Red gold, sterling silver, 585 gold | Increases hardness, adds red tint |
| Silver | Yellow gold, white-gold base alloys | Lighter colour, more ductility |
| Palladium | White gold (hypoallergenic) | Whitening, reduces tarnish |
| Nickel | Older white gold | Whitening (allergy potential) |
| Zinc | Solder alloys, yellow gold | Lowers melting point, hardens |
| Iridium / Ruthenium | Platinum alloys | Increases hardness of platinum |
Effect on material value
The melt value of a piece of jewellery rests exclusively on the fine weight of the precious metal, not on the weight of the alloying metals. A 585 gold ring weighing 10 g in total contains only 5.85 g of value-relevant fine gold; the remaining 4.15 g of alloying metal (often copper and silver) barely enters the valuation. You can work out the exact material value with the Melt Value Calculator.
Fine weight = gross weight × (fineness ÷ 1000)
Example, 585 gold, 10 g: 10 × 0.585 = 5.85 g fine gold
Colour driven by the alloying metal
The colour of a gold alloy depends directly on the ratio of the alloying metals blended in:
- Red gold / rose gold: high copper content (e.g. 750 parts gold + roughly 200 parts copper + 50 parts silver)
- White gold: palladium (hypoallergenic) or, historically, nickel replaces the copper entirely
- Green gold (electrum): high silver content, little or no copper
Tarnishing and allergy risk
Copper and nickel used as alloying metals can trigger contact allergies in sensitive wearers. Nickel is tightly regulated across the EU for jewellery, piercing jewellery and skin-contact articles — the original Nickel Directive 94/27/EC was superseded and further tightened by the REACH Regulation (EC) No 1907/2006, Annex XVII, entry 27. Palladium is regarded as a more tolerable alternative. Silver develops a dark tarnish layer through airborne sulphur compounds, and the alloying metal copper speeds that process up.
In brief
The alloying metal governs the colour, hardness, allergy risk and tarnishing behaviour of a precious-metal alloy, yet it has no material bearing on the precious-metal value itself — that is determined solely by the fineness of the precious metal.