Published: 01 Sep 2017

How to Check Gold Purity & Understanding BIS Hallmark

How to test gold purity at home?

January 1, 2017 brought a welcome change from the Bureau of Indian Standards (BIS). The BIS revised the Indian standard on the gold hallmarking; mandated BIS licensed jewellers to hallmark the ornaments in three categories. Thus, the gold and gold jewellery is bifurcated in accordance with their fineness in grades of 22, 18 and 14 Karat. The guidelines are levied to protect the interest of the consumer who seeks gold jewellery in various karats, depending on their financial capability.

Gold, being a soft metal, is usually alloyed with other metals such as silver, copper, platinum, or nickel. The purity of gold and proportion of alloy is measured in karats; with 24 Karat being pure gold. One karat would mean that there is one-part pure gold and 23 parts alloy, and six parts of other metal mixed with 18 parts of pure gold would form 18 Karat. Thus, 24 Karat is the purest form of gold, on the other hand, six parts of other metal mixed with 18 parts of pure gold form an 18 Karat.

It is essential to verify the fineness of gold to ensure its value. It is believed that you can test the gold karat at home, with an assay test kit. This kit helps the user identify the purity of the gold, and can be found on various online platforms. It consists of a touchstone and different solutions of dilute nitric acid in separate bottles labelled as 14K, 18K, 22K and so forth. The stone is a dark acid-resistant rock such as slate.

3 Ways to Take Gold Purity Test at Home

  1. Rub the gold ornament on the stone to create a streak mark.
  2. Apply 2-3 drops of acid from the bottle marked “14K acid” to the streak.
  3. If gold changes colour, then the jewellery is either 14 karats or slightly below the level.

However, if the colour remains same, continue to test with higher-karat acid bottles i.e. 18K, 22K etc, till the ornament changes its colour. This will indicate that the ornament’s karat is less than or equal to the last karat-acid that was used.

Please note that this is an exploratory test. If the test results are below your expectations, please visit a government approved jewellery assayer to evaluate the exact worth of your gold jewellery.

Know more about difference between various gold karats here