Testing gold with an acid kit

So you've started buying gold. You know how to identify the gold content in pieces of jewelry by the stamps and the weight. Sometimes you run into broken pieces of jewelry. Some pieces don't even have a stamp but the owner swears that they're real. Maybe you're trying to buy a coin that you're not sure about. So what do you do to make sure that you know what you're buying? Never fear. There's a very inexpensive solution. Just get a gold acid test kit. You can get them from Amazon or Ebay for around $30-$40. So what do you get?

There are a lot of different varieties of kits that you can get. The kits generally consist of several bottles of acid and an acid test stone. Some kits will also include a digital scale and/or a jeweler's loop (which can be a great value if you don't have either). Some also come with extra acids. You can get acids to test silver, platinum, 10k, 14k, 18k and 22k gold. The cheapest kits come with 10k, 14k and 18k acids and a testing stone. Get an acid kit with all of the acids needed, a testing stone, a jeweler's loop and a digital scale and you really do have all of the equipment needed to buy precious metals with confidence.

So how the hell do these acid kits work? It's not that tough. You rub the piece that you want to test on the testing stone. Then you apply the appropriate acid to the line and see what it does. If you're testing silver or platinum then it's just a one stop shop. 925 (sterling) silver turns a brown-dark red color. If the piece is only 75-90% silver then it will be a lighter red. If it's 65-75% silver then it will be a light green. Here are a couple of the pics of the silver test. The coin on the left is an old 80% silver Filipino peso. The ring is sterling (92.5%) silver. It's a little hard to tell against the black of the stone but you can tell that the coin tested much lighter than the ring. If you're testing platinum then it won't do anything when you apply the platinum acid to it if it's really platinum.

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Gold is a little bit more involved. Because of all of the different ratios of gold there are a lot of different acids to test it. 10k gold has a much different makeup than 24k gold. Overall, though, it's not that complicated. Basically, if you make your line and it dissolves quickly when you apply the acid then you should try a lower grade acid. Keep working your way down until the line doesn't dissolve. Obviously, if the piece is stamped 14k then it's a waste of time to start at 22k and work your way down. If the line doesn't dissolve with the 14k acid then you know you're good.

In the case of the ring that I recently bought it's not stamped at all. It's set with a 1/10th gold eagle so, realistically, the ring should be real (yes I tested it before I bought it).

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So if it's not stamped what's the quickest way to figure out what grade the gold is? Here's what I did.

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I just scratched a line across the stone. Then I applied a drop of 10k acid at the top, 14k acid in the middle and 18k acid at the bottom.

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As you can see the 18k acid dissolved the line. The other two drops dissolved nothing. The ring is 14k.

Another way to do it is to compare a piece that you know is 14k to a piece that may be 14k. Just make a line with each of them and use the same acid on both. If the piece that you're testing dissolves more quickly than the control then it's a lower grade. If the control dissolves and the line that you're testing doesn't then the test is higher grade. In this pic I used 18k acid on an 18k bracelet and my 14k ring. You can see the difference.

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So there you have it. These kits are really simple to use. Gold filled and possibly gold plated jewelry might fool you if you're not pushing down hard enough but gold plated jewelery has such a thin plating that I don't see how the plating could stand up to a swipe or two across one of these testing stones. Gold filled jewelry is a little bit more durable but if the piece looks like it's dissipating even with 10k acid and it's supposedly a higher grade then it could be filled. Case in point:

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That's a 12k 1/20th filled necklace reacting with 10k acid. As you can see the line is cloudy and falling apart in the acid. 14k acid would probably completely dissolve it. If it was a real 12k piece then the 14k acid would probably make it look somewhat like it does with the 10k acid.

I hope this helps. I'm starting to find out that this is a good way to make cash on the side. As long as gold keeps going up then money will keep on being easy to make. You just have to know what you're buying, know where to go to get the best deals and know where to go to sell what you've got. So where do you go to sell your cache when it's finally time to cash out? Hmm....


Anonymous said…
I've picked up some gold leaf off ebay.I'm wondering if I should purify it with aqua regina.I think it would be good on gold plate and such.
Dean in az
I don't like gold leaf or plated/filled jewelry. Some filled jewelry has enough gold in it to be worth something but for the most part it's not worth the space. It's also not worth the time and effort to extract the gold unless you plan on doing it a lot. Everything that I've read about gold recovery is that it's dangerous, uses highly toxic chemicals and shouldn't be tried unless you have a facility dedicated to it. Of course, there are a lot of guys out there who are doing it themselves. I'm sure that some of it is just overhyped propaganda from the people who do it for a living to discourage normal joe from trying it in their garage. Then again, some of the chemicals used to do it efficiently really are bad juju. There are safer, less efficient means of doing it but I have absolutely no idea how much money there is to be made. If anyone has any experience with it I'd love to hear from you! artyboy at gmail dot com.
Anonymous said…
Off the top of my head,I'd assume that the acid in your test kit is probably aqua regina,as it dissolves the gold in the same way.
My other issue would be how to prove its purity to someone without the kit.
Dean in az
It's not aqua regia. There are a few different types of acids that are used. I can't remember them or the mixes off the top of my head. The biggest mistake that people make when they're arguing whether or not gold will be "worth anything" is that they think that they'll be taking their gold coins down to the grocery store to buy a loaf of bread. That's not how it works now and it probably won't work that way anytime soon. You take your gold to someone who knows what it's worth and is willing to give you money for it (or whatever the recognized standard for trade is) and then you go buy what you need.
Anonymous said…
I didn't mean to use aqua regina as a test method.You mentioned that in your yard sale finds,you got a lot of plate or filled with the good stuff.What do you do with that?
My intent was that when you accumulate a good pile of it,recover the plate and filled gold from it.
Dean in az
I just toss it on ebay when I get a good sized pile. If you break down the gold content in the auction you'll almost definitely get spot at the very least.
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Ryan said…
I was curious about what kind of test kit you had and how you liked it.
I bought my test kit on ebay. I think I paid around $30-$40 for it. They all use the same mix of acids. Just make sure that you get a kit that does 10k, 14k, 18k, 22k and silver at the minimum.
It's hard to determine what real gold is without a test kit. If you're buying gold, you must keep this handy to detect the fake ones. Or at least, you can get the 18k that you want. :)

Anonymous said…
what is the testing stone/ ceremic/ slate/ect,

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