Acid Testing Precious Metals

Acid testing is a qualitative metallurgical assay (compositional analysis of an ore, metal or alloy) which uses acid to distinguish gold, platinum and silver from base metals. The test is very accurate and is regarded a definitive test for the quality of a metal. Figuratively, ‘the acid’ test is regarded as the ultimate test for some attributes including a persons character or the performance of a product or service.

The test includes rubbing a piece of metal on a black item such as a black stone, which will leave a visible mark on the stone when carried out correctly, without damaging the metal being tested. The mark on the black stone has aqua fortis (nitric acid) applied. Any mark that is not gold will dissolve rapidly. If the mark remains, the area is tested with aqua regia (nitric acid and hydrochloric acid). If the mark is then removed, it is proved that this test removed the mark of gold from the stone proving the metal to be genuine gold.

At Vintage Fine Jewellery every piece of jewellery is acid tested, even when pieces are hallmarked. We carry out accurate testing on all vintage jewellery to define the fineness or purity of the precious metals, therefore we are able to list the carat grade of the gold.

The jewellery specialist at Vintage Fine Jewellery has over 25 years experience with fine vintage jewellery, supplying some of the most prestigious jewellery stores in the United Kingdom with vintage jewellery for many years.