Testing Gold Using Acids
By Rubina Posh April 17,2017
You will need a 10x loupe, the acids, testing stone to scrape the metal onto, tissues and disposable gloves.
Please note that the acids will stain your skin, (it is corrosive) so be careful not to spill any on yourself and don’t get any in your eyes (it is recommended that you use protective glasses)
- Inspect the piece for official markings. Look for noticeable discolouration.
- In a discreet spot scrape the piece onto the touchstone. Make a longer streak to be able to test it with multiple acids if necessary. Gold will be soft and easy to scratch and the streak will be yellowish in colour. Look at the spot where the piece has been scratched. If it’s a different colour, silver like or brownish, then it’s an indication that the item is plated.
- Start with the lowest acid and work your way up. Using the dropper, put a small dab of acid on top of the streak. If the streak dissolves, the gold is less than the karat on the bottle and you should try again with the next acid unless its 9k, in which case you probably have a plated piece.
- If the acid dissolves the streak slowly, it’s possible your piece is a bit less than the karat of the acid in the bottle. If the streak stays, it’s most likely the karat of the acid in the bottle.