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Determine the exact weight of fine metal to add to reach your target purity (e.g. from 800‰ to 925‰).
Calculate exactly how much fine metal or master alloy to add to reach your target purity.
Add pure Gold/Silver (Fine)
+ 166.67 g
New total weight
266.67 g
Alloy purity upgrading (titre raising) increases the precious metal content of an existing alloy by adding fine metal. In Swiss jewellery workshops, this is common when moving from 750‰ (18 karats) to 833‰ or 875‰ to meet a specific hallmark requirement.
The base formula is: Fine metal to add = (Target purity − Current purity) × Current weight / (1 − Target purity). This formula assumes you are adding 999‰ fine metal. When adding a master alloy, its own purity must be factored into the calculation.
Swiss goldsmiths maintain a metal ledger (Metallbuch) where every purity adjustment and smelting operation is recorded. This ensures ESTV compliance and facilitates checks by the precious metals control office (METAS).
Prices shown are indicative (LBMA mid-market). They do not constitute investment advice.