QuestionHi I bought an acid tester from ebay and it came with the stone to scratch the jewelry on. It came with different bottles of acid to test for 10k, 14K and 18K (as well as silver and platinum tester bottles). The direction said to scratch the jewelry on the stone, then start with the lower acid, if it dissolves, it means it's not gold at all, or if it dissolves slowly, it might be of lower karat. I find this quite difficult because sometimes it's not clear if it's really dissolved or if I just didn't scratch hard/thick enough. Is there a way to use these acids to test more accurate (like filing off the jewelry) and testing directly on the jewelry? If so, how do I use the different 10, 14 and 18 acids. And my second question is, how do I test 14k or 18K white gold?
Thank you in advance!
AnswerJinny, welcome to my answer site and glad to have this fine question.
I will first direct you to this resource, Shor International. This supplier of jewelers tools and supplies does one thing quite well that many other suppliers do not do.
They provide instructions and in some areas of the work the papers are quite technical and detailed. Visit the web sites below when you can. Certainly visit the second link which is how this company suggests using acid testing kits. (Links are copy and paste.)
Shor International Gold Testing Kit, Acid Testing
http://www.shorinternational.com/TestGold.htm
Instructions for Acid Scratch Testing
http://www.shorinternational.com/TestGoldScratch.htm
I will answer this part of your question first, your question about using the acids directly on the metals. Generally, this sort of test is not used to determine karat but to see if the item reacts like a gold filled or plated item. The result over copper based alloys is a green bubbling which does not happen with karat gold. The file mark and apply acid will tell if gold or not but is not an accurate way to determine karat. Essentially, you will get more discoloration on lower karat golds but comparison is difficult. Try the file and apply method if you wish then use the scratch test to better determine the karat range of the gold.
TEST NEEDLES
Test needles are a group of rods connected together so each is easy to use individually. At the end of each rod is a piece of gold of a known karat quality. The needles provide you with a known karat for comparison with gold you are testing. Using the known sample and testing with acids is the most accurate method of using the scratch method.
This is what you do: Make a solid and firm mark from the item to be tested. Make a mark a test needle or with two, guessing which karat the unknown item might be and using a needle on either side. If you suspect the item might be 14k, make a mark and also make a mark for 10k needle and a 14k or 18k needle. Apply the 14k acid and see what happened. Put the acid in a fine line across all the marks, leaving some of the marks untouched so you can use another acid if needed and not have to remark the metals on the stone. Compare the color and rate of dissolve of the unknown and the known samples from the needles. If the sample is the same color after the acid as the 10k needle for instance, and the 14k mark is pretty much unaffected, then you have a item which is likely 10k. If the 10k mark is gone or very diminished and the unknown is looking in color like the 14k needle mark, then you likely have 14k. The idea is to make marks which you know are a certain karat and compare this to the unknown one. You can do this even if using the wrong acids. Use for comparison of color and faded nature of the sample and the known needle mark.
As for white gold, the acids will work on the nickel making the gold white (generally it is nickel) and the resulting smear will loose that color and be yellowish, looking much like the results of the acid on a scratch of yellow gold. Use the needles the same way, using yellow needles. If you have a piece of jewelry of a known karat in white gold, try using a scratch from it to compare with an unknown white gold sample.
The advent of palladium as the white maker in some white gold alloys makes the testing more difficult. I have not tested much palladium white gold with the acids. I believe the test will work essentially as it with the color essentially floating away but will try this more extensively when back at work and let you know with a follow-up if needed.
What I have said should work ok for you. Either get test needles or use gold jewelry of a known karat as a sample. Having a comparison of known karat gives you a direct view of how a certain karat reacts with the acid, regardless of the acid used unless strong enough to dissolve it instantly.
Jinny, best wishes with the testing. Get back to me if you need to do that.
God Bless and Peace. Thomas.
