Using 3rd Party Assays

The Melting Bar uses 3rd party assays laboratories that guarantee that all precious metals are tested using the most appropriate techniques of assessment.

Gold, silver, platinum, palladium and rhodium are assayed (determination of precious metal purity) in various ways to accurately and precisely assess each metal's percentage of purity.

The process known as "fire assay" is the oldest known technique of assaying gold and continues to be one of the most precise method. When gold is melted, a sample of the gold is taken, either by drilling through the poured bar or by capillary tube sampling while the gold is in a molten state. The sample is weighed very precisely and the amount recorded. The sample is wrapped in assay lead foil along with a quantity of pure silver. This wrapped ball is placed in the furnace in a cupel. All the non-precious metals are immersed by the hot cupel. The precious metal forms a button within the cupel. The cupel is removed from the furnace and the button is brushed to remove any remaining bits of the cupel. It is pounded flat, rolled thin and then heated in a porcelain crucible containing a weak nitric acid solution. The acid removes the silver, which is poured off and the silver recovered from solution. The gold is then washed in distilled water to remove any residual acid and then dried out.