When examining a Gold piece of KARAT jewelry, sometimes looking and identifying the gold jewelry Hallmarks is not enough. For this reason we have the Gold Acid Testing Kits with us at all times when buying gold.
So... how does it work?
Gold Testing Kits includes test solutions for different KARAT jewelry, 10K, 14K, 18K, 22K and sometimes also includes test solutions for Silver and Platinum.
The test kit will usually include "fingers" or "needles" rated with the different karatage and used as control against your test piece.
Test kits comes as well with a Touchstone , Touchstone has a finely grained surface on which soft metals leave a visible trace when striking them with some force.
On the Touchstone we strike a line of known karatage item (i.e. our control) and right next to it we strike a line of the unknown item we want to test and apply a drop of the appropriate test solution on both lines and looking at the reactions at each one of the strikes, our test and the control.
-- If the test strike disappears (i.e. metal dissolve) just before, or at the same time as the control strike, then you know your tested item is at the appropriate karatage.
-- If the test strike disappear immediately then add a lower karatage control strike (control 2) and apply a lower karatage solution on all three and notice again the reactions, the control strike should not be effected or to be effected at a slower rate than the test strike and control 2 should be similar to the test strike.
-- If the test strike disappear long after the control strike or does not disappear at all, then try to apply a higher karatage solution on both the test and control strikes, the control strike should disappear and the test strike should slightly be effected or not at all (although, hard to imagine someone will make a 18K piece and mark it 14K).
Please remember, Observation time with any test is 10-20 seconds, longer then that the test is no longer effective, with time and experience one can learn how to interpret the attack rate of the acid on the metal, the colors it produces etc'..
As you can probably understand by now, it's a game of comparison between a known and unknown samples.
Say we have an unmarked ring, and seller claims it is a 14K gold.
Simply strike the ring along side a control 14K strike, apply 14K test solution and watch.
- Reaction is similar, the ring is 14K
- Ring strike disappear faster then the 14K control, add a 10K control strike and apply a 10K test solution on all three strikes, if ring strike still disappears faster than the 10K control, it's most likely not gold. If disappear slowly then it might be 9K gold ring, if reacts similarly to the 10K control - than it's 10K gold ring.
Acid Gold Testing is not just for the Pro's, the common man can easily learn how to test Gold, Silver and Platinum and with few trial and errors you will become an expert, becoming a better gold buyer and helping friends and family with their jewelry.
You should know that Acid Gold Testing involves hazardous chemicals (nitric acid, Hydrochloric acid, potassium dichromate) and testing must be done with latex gloves, away from people and in a ventilated place. Make it a habit for yourself to keep and store all of the paper used to wipe down the used liquids from the touchstone as there are some traces of dissolved gold on it, once accumulated they can have a recoverable amount of Gold.