Acid testing for gold, silver & precious metals

A. Hi, Anthony. If the antique store claimed that it was Sterling, I think they owe you!

But assuming you did not pay the gold-buying shop to do an appraisal of your find, I wouldn't be hard on them; you misunderstood each other. If you didn't pay them anything for their time & effort in evaluating your find, the assumption is that the reason they were doing this for free is that you would like them to make an offer to buy the silver for its intrinsic (melted) value. They tested the surface without devaluing the item and told you there was silver on the surface but they were unable to tell you if it was just plating (worthless) or solid silver from that. You asked them if they were interested in buying it and they said they couldn't answer without cutting the item in half. They apparently feel that it isn't silver so it has no scrap value. Sorry for the disappointment :-(

Regards,

A. As stated earlier, you can use a scratch stone when testing silver/sterling silver with a test acid. Scrape your piece on the stone in several spots. This will help get you past any plating that may be there. Check out the color of your scratches on the stone. They should all be silver in color. If you get any other colors, such as tan, it is not silver. Now add a drop or two of your acid and wait about 30 sec. Don't wipe the stone because this will remove any of the material and the acid and will leave the stone clean. Instead, rinse the stone off under the faucet and check the color of your scratch. It will be red if the piece is silver. This technique has worked well for me for over 20 years. I do replace my acid at least once a year.

A. Anthony Salas: If the metal turned black when acid was applied it is very possible the item is 800 silver which is almost as valuable as sterling. I have acquired items in the past that were marked 925 or sterling only to find out it is 800 silver instead.
Next time you take your silver in question to be tested first ask yourself what you intend to do with the item if it is not Sterling. If you plan to keep the item or try to sell it or return it then you will want to test it without damaging the item. Also ask yourself if it is sterling what are your plans for it. If you plan on keeping it or selling it you would want to use the least invasive yet accurate test available. Using a strike plate is your best choice -- just make sure to use an inconspicuous area to scratch. The same if you have to scratch the item itself. Keep in mind the acid can be removed from the item, the same as any green that may appear if the item is plated, but the acid will remove the plate and expose copper or brass if present so the smaller the test area the better.
I've heard horror stories about people taking items to be tested only to find out the item is plated but the tester destroyed the item in the process without giving any consideration as to what you had intended to do with said item. So it is very important to inform the tester of your intentions prior to handing the item over to be tested. Never rely on the tester asking because he may forget and you may become distracted and forget to tell him. The more control you have of the situation and the more knowledge you have of your item the less likely mistakes will be made and the less likely you will be taken advantage of.
Hope this helps.

A. Most "gold test" chemicals are in fact various strengths of "Aqua Regia",(the strength depends on the karat value), The primary purpose of the testing stone is that it removes a thin layer of gold to its surface, the aqua regia solution will completely dissolve the scratch if the item is in fact lower than the karat value of the test. Someone stated here that the test was %75 Hydrochloric(muriatic) and %25 nitric acids.....This is in fact (at these percentages) a solution called Aqua Regia which would dissolve even 24k pure gold, therefore would not in any way be suitable as a testing mixture.
I have seen many comments about using nitric or pre mixed gold test solution for testing silver, This is in fact correct. When testing silver with a gold test solution or nitric, sterling or pure silver will turn the piece milky white as stated, , and any gold test chemical above 14k will generally break the barrier between the silver plate and any base metal.
While testing gold on the stone is preferable, silver should generally be tested directly on the piece, if using 10 or 14k test solution you should leave the drop on the piece for at least a full minute so that the solution can have a chance to break through any plating to the base metal. After testing, the white spot can be buffed out again leaving your piece in its original condition....if the piece is silver plate, you may (or likely will) end up with a permanent spot where the plating has been removed.

A. I put a drop of the silver test acid directly onto a Rogers "deluxe plate" spoon, and another drop directly onto a silver US dime. I knew the deluxe plate was pretty thick, because I had rubbed it real good on a stone and that had still tested sterling, and there was no visible copper alloy on the rubbed area of the spoon (I already knew the base was a copper alloy from other damage to the silverware). Anyway, applying the acid directly onto each item, both turned blood red, then the liquid turned pretty much colorless, and there was what looked like a dark gray stain on the metal under the liquid in both cases, with just traces of red. Then I rinsed. The plated piece was deeply etched, but not the dime. I had to turn the dime at an angle to see where it was slightly dulled. The difference was subtle, and almost certain to be overlooked at a casual glance. I then applied a second drop to the silver plate, rinsed, then applied a third drop. The third drop turned blue-green. I imagine there are some pieces out there even more heavily plated than this one, but this might be a helpful testing technique to discover heavy silverplate if all you have is the silver acid test.

A. You guys are doing this all wrong! Why would you damage your silver bar or coin etc..?
What you need to do, and is much more accurate as well as non-damaging to your silver, is a water displacement test. I am a Chemistry Major, I can tell you that this is "Chemistry 101". It's very easy to do!

- weigh the silver piece on a digital scale ⇦this on eBay or Amazon [affil links]
- fill a beaker with water
- read and record the water level (in milliliters)
- put silver bar, coin, irregular shaped, etc.. in beaker
- read and record the water level again
- record the difference in water levels.

This information will allow you to determine the density of the object. The density for silver should be precisely 10.49 gm's per ml.

This seems a bit more cumbersome, but most likely the very best test. Kind of like a DNA test for metals.

Formula below:
Density (should be 10.49) = weight (grams) / ml of water displacement

Thanks, Chuck. Good idea! But I'd call that a quick "disqualifier" test to show that something is not silver, rather than a "DNA test". Because it's pretty easy to mix together a metal that is heavier than silver with another metal that is lighter than silver, maybe leaded pewter for example, in a proportion so as to get 10.49 g/cc.

Regards,

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

A. The Alternative way to test for silver with the Acid sold on eBay is to first of all get a clear full glass of water ready, get your Acid ready and an object like a file suitable to file a metal surface that can be used to file a small area of what is suspected to be silver metal.

File this very well and deeply to accurately test for silver instead of getting confused with silver vs silver plated.

When you are done filing very well put a drop or very little drop of the Acid over the area that was filed.

You should notice a reaction in that area, that acid kind of turns milk color and the silver changes to kind of gray then immerse that section/area into the glass cup of water then a further reaction with the water should show what looks white like a smoke going down the cup, kind of cloudy.

"Hand-Held X-Ray Analyzer

on eBay or

Amazon

(affil links)

A. Hi Daniel. If you have a friend who works in a scrapyard, he may well have an alloy sorter hand-held X-ray fluorescence tester ⇦this on eBay or Amazon [affil links] . These are very expensive, around 40K, but are non-destructive and so handy that many if not most scrapyards have them.

Luck & Regards,


Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

A. Hello,
If you test with 18k acid a sterling silver piece will turn a milky blue color immediately. Ive researched this and tried it and it does work. So try the 18k acid to test silver. If you test something you know is silver first you will see the color the sterling turns.

A. R Knuth,

Green usually means that it's just a silver plate over base metal. Take the time to read through the linked article for further information:
www.lacywest.com/t_goldt.htm

A. Hello R Knuth,

You can see this video:

In this video, you can see that the alloy is very high in copper, so it reacts with nitric acid rapidly and turns it green (from cupric nitrate). If this was real 925 silver, you may see a creamy color in the nitric acid, and not so many bubbles. This is not a failproof test, there are other alloy metals in fake sterling silver, but it is one.

Hope this can help! Regards,

A. Hi, I do a lot of testing.

Firstly do not buy from eBay , use a reputable jewellery supplier
Second Yes acid does go off.

Testing: First I do by sight (you cannot use acid on other peoples items if in the field)
The scratch stone should be alright; mine has been.
If I am still in doubt I then do a destructive test

If sterling it will come out red.
If above sterling like a lot of Mexican jewellery it will turn bright red.
The less red the less silver content but the piece could still have some silver in it.

Never try to use a magnet to be sure. If you do not know your metals the magnet is one of the worst leads you can get. I use a magnet sometimes but I know my metals and I still make mistakes myself.

I buy at flea markets, etc. Mistakes hit me in the pocket. It is a gamble -- even dealers will try to convince you things are silver or gold when you can plainly see they are not. But a lot of dealers do not know themselves so be careful

Hope this helps

Georgia

A. Just as a quickly.

With regard to the comment "Acids go off", can I please make a slight correction--

Also as a note to the wise, the most conc. nitric acid you can normally obtain is around 67 - 68% and with hydrochloric acid, around 35-37%.

This is already taken into account with the 3:1 Hcl / HNO3 mixing ratio - though Aqua Regia

All the best,
Mark

A. Hi Sorrell!

I am sorry, but your piece is a fake. Green implies copper, and bubbling implies NOT gold. The nitric acid test is generic for precious metals.

Regards,

A. Sorrell,
It's possible that the clasp is not a high purity gold or a different metal and perhaps the chain is still authentic. Gold clasps are used in many cases but if the clasp is another metal it tends to be more sturdy, especially if the chain is high K. If the clasp is marked as gold of a certain K, that is a bad sign, it should not be marked as such if it is testing negative.

A. I use a commercial silver tester from amazon, a small bottle of dark liquid. It works for about a year, then DOES go stale, showing no reaction at all. I rub the test area with a gray eraser first.

With fresh solution, silver turns shades of red, depending on how much silver there is. If there is any red, I'm happy. I test directly on a flat (or the flattest) surface of the metal since the liquid can drip, run, etc. Also since this is acid, albeit weak-ish, watch you fingers and test only over a junky surface not painted, etc. I keep a wet towel nearby.

If suspicious of silver plate, scratch a good THIN notch in the piece and test with a small drop of solution (got this from a jewelry book).
ALSO: look at the edges where wear might be, as in a bracelet with angles rubbing against each other. A golden tone is probably brass or copper underneath with wear in the silver plate (!)...of course a wipe with a good silver cleaning cloth first sometimes gets rid of the "gold" which could just be tarnish.

For GOLD, I use a small machine: MIZAR M24 ⇦this on eBay or Amazon [affil links] , which is pricey, but I've had it for years. It also requires a liquid which goes stale after about a year or so.

Both liquids depend on how often you open them. I open them ONLY when I'm ready to use, then quickly close, AND put into a second tight container...both can last more than a year (rarely).

The Mizar is extremely accurate, but you have to follow directions. Considering how expensive gold is now, frankly, I think spending a bit more to test for it is worth the cost.
Also, eventually (after years), the well with the metal in the Mizar which has to be cleaned (scrupulously) will wear out, as mine is now.

Oh, and after testing silver, don't delay wiping off the acid. I rub it with a gray eraser and then sometimes a silver cleaning cloth. Sometimes it requires silver polish, and sometimes the gray spot left after the acid needs to be buffed by machine.

Been doing this for years with about 95%+ accuracy ... my only errors come when I don't realize that the solutions are shot. But then I just go to a known entity to verify the quality of the solution and know to buy a new one.

PS: If the Mizar shows a low reading but the metal looks good, it "might" be Palladium (a bonus). The excellent instructions address this.

Also: Beware of "alpaca" for Mexican material. Alpaca looks pretty good like silver but has NO silver in it. It is often marked, but often not. With practice you can almost tell by just looking and handling it.

And "German silver" is another stinker: no silver in it ... everything but the kitchen sink, but no silver.

A. I do not have any problems with the [brand name deleted by editor -- huh? why?] test kit solutions I've used at all. I use a loop magnifier to see the reactions and they are readily visible that way. The angle of light, the best being natural light from a window, is also important. In particular, Sterling silver turns milky with the other instruction colors being spot on for period/age of pieces of jewelry and buttons. Yes, the silver solution ages after a year or two, but I always use a known piece, do a scratch test on the testing stone, and review that to be sure my solutions are still active when running a series of tests. BTW...no one mentioned here that Rhodium, often used in jewelry and buttons, does not react at all in acids and that it is also impervious to platinum solution. Rhodium is bright silver in color and seems almost artificial and can be made into rather thin materials. I just found a set of two gorgeous impala designed "picture" buttons that retain their lustre and are almost certainly Rhodium as per the above. I buy a new kit after 2-3 years just to be sure and this has been fine and not resulted in any issues when I've sold on EBay with notations about the test kit results included in my descriptions. The scratch test on the stone does no harm. Shake the bottles before use.