Confused about "acid test" for silver and other precious metals
A discussion started in 2001 but continuing through 20182001
I would be grateful if anyone can supply any information about how to understand the different carat of gold? Is there any solutions to purchase or to prepare which would tell me the exact carat of the gold jewelry? Thanks in advance. FatmaFatma A [last name deleted for privacy by Editor]
Q. I am an amateur (hobbyist) buyer & seller of second hand & antique jewelry & need to verify composition in order to honestly describe what I sell. Recently bought a testing kit on eBay. The silver testing bottle is dark amber in color. As a trial run, I scratched the stone with various silver-colored metals--anything from steel to marked sterling to "mystery" metal. I observe no reaction whatever with any of them. Does the reaction occur instantly? Can I use another type of stone instead of the dark gray one that came with the kit? Or could the liquid in the bottle be defective? Instructions with kit were very sparse. Would appreciate any suggestions.Jane Bagg
hobbyist - Punta Gorda, Florida
A. I've never used a jewelry test kit, but I am a chemical engineer, so I'll make an educated guess at your problem. My first guess is that the liquid in the bottle is some sort of acid, either nitric acid or a 75% nitric acid/25% hydrochloric acid mix also known as aqua regia. I know you will get a reaction from either silver or gold if they come in contact with either acid, although off the top of my head I don't recall what color you'd get. But there would definitely be a change, or else the metal would completely dissolve. You should see a reaction right away, in under 30 seconds. And yes, it's possible that the acids could go bad over time (say a year or longer) or if the bottle wasn't sealed.
My second guess is that the purpose of the stone is to scrape off enough metal to get a reaction to the acid without doing too much damage to the object you're testing. So the stone just needs to be sharp and resistant to acid. Is it possible that you didn't scrape off enough of a sample on the stone to get a reaction?
If you have an item that you know is silver and don't mind it getting damaged, you could take a drop from the bottle and apply it directly to the silver and see if you get a reaction. No reaction means the liquid is bad, any reaction means you didn't get enough sample on the stone. Or you can write off your e-bay purchase and buy a new test kit with instructions; try typing "silver test kit" into Google. If you have access to a local junior high or high school with a chemistry lab you might be able to sweet talk a teacher into testing your liquid or some of your objects, especially if it could be worked into a classroom lab practical and/or demonstration.
Hope that helped. Good luck with your hobby.
- Orland Park, Illinois
I bought a similar test kit off of ebay from a guy who sells many such kits. It included 3 bottles for different purities of gold and one bottle of solution for testing silver. I believe the gold solutions would be the aqua regia and the silver solution is most likely just nitric. Anyway, when I first used the solution it worked very well. Anything made of sterling or purer would immediately turn the solution a blood red color and the silver (if I had put a piece in directly)would turn very dull. The solution also bubbles as it is reaction with the metal. I often would get bubbles with other metals, but the solution would turn blue (copper indicator I believe)or yellow. I have now had this same bottle for well over a year and it does not appear to be working any longer. In fact, that is why I was on the internet searching "Does silver testing acid go bed?" I am guessing from your experience and mine, and the other persons comments that the solution does, in fact, go bad over time. :( Guess I need to buy a new bottle myself. The first one did work a good long time, though.
- boulder, Colorado
April 3, 2008
I recently purchased the silver test kit. It seemed to work well as I always had an instant reaction after applying it "to a piece of silver". The instructions say that bright red reaction is "true silver" and dark red or cream color is "Sterling" / or greyish-brown "77%-90% and light green color is 65%-75%. I have a dilemma, I was hoping someone could help me out with. I put a drop of the solution on this gravy boat that I bought at a thrift store. The first reaction was bright red, then it went to a dark red and stayed dark red (forever). I was confused so I went to a pawn shop and asked them to test the piece. They told me that the only way to be sure is to actually cut the piece because the silver plating might be really thick. So I cut the clawfoot of the piece and got a lot of bright silver shavings. I cut it pretty deep, then applied the solution and it turned greyish/black? I did this several times with the same reaction. Can anyone tell me what I have here? pure silver? sterling? Nothing? lol I would greatly appreciate it. Thanks so much.
- Sioux Falls, South Dakota
May 4, 2008
A. I have done a bit of testing on various silver colored objects I have. With my NEW bottle of silver test solution (My previous problem was that my solution had gone bad, I would get a reaction just as you describe with any item that was silver plated. I tried this on some old silverware that was marked as silver plate and got the same reaction. My best guess is that what you have is fairly heavily plated with pure silver, hence the initial reaction of the bright red. My guess as to why it stays dark red even after a long time, is that the plating is heavy enough that the solution is used up before it eats through the heavy plating. Your test after the deep cutting shows that the metal underneath is not greater than 75% silver, though my guess would be it is not silver at all. You are getting some reaction as there is still some of the silver plate touched by the test solution. You could try putting more solution on the first area you did to see if you can get thru the plating. It may take a couple of tries depending on the thickness of the plating. I believe your deep cut test already gives you your answer that it is a silver plated item, and reapply solution to the previously tested (but not scratched)area will merely confirm those results.
- Boulder, Colorado
July 22, 2009
Q. This is interesting, glad I checked, not sure I want to buy a testing kit now. I have been buying & selling silver-plate & sterling for years, just started to step it up a bit and advertise for scrap sterling. Sometimes I run into Mexican Sterling, not sure a test kit would help. I guess I will shy away from it unless it is marked with some kind of verifiable mark. I was surprised that the test kit would react to silver-plate (which is silver) the same way as sterling. Silver Electroplate is silver but so thin you could rub it off with light sandpaper. Then there is Sheffield Plate which is Sterling with Copper sandwiched in the middle for weight & durability. Then there is Nickel/German Silver, which is a mix of Sterling and other metals. A test kit would be useful for that. Most US & European sterling is clearly marked. I think I will rely on that.Richard Rogers
- Kona Hawaii
January 12, 2011
A. A small correction. German silver does not contain any silver at all.Herbert Fellows
- new york, new york
March 1, 2010
Q. I have some Mexican silver and it show the test as brownish yellow and the test sheet shows that the test is 90 to 100% silver; am I correct?ray robey
hobby - temecula California
May 28, 2010
A. The test colors for silver that you have posted appear to show silver content at 80% silver but the yellow reaction indicates a base of tin which would be common in Mexican silver.Kerry McGee
- Prescott Arizona USA
August 30, 2010
Q. Ok .. so I know something about testing for silver.. But what is the color yellow mean? No silver? Bad solution?laura andersen
March 25, 2011
Q. I am totally new to silver and color blind LOL!! I am only interested in purchasing .999 rounds and bars for investment sake. What are my best choices for testing in this situation? Is acid the only way to determine quality? Would appreciate any help!Ron Cox
- Mesquite Texas USA
March 31, 2011
A. If at odds for testing silver, with acid try using any gold acid to the silver; it'll turn milk white and stay milk white. If silver is plated the gold acid (10 kt--up) will eat through the silver plate and start eating the base metal, by bubbling and acid will turn green. it's a foolproof method, and you clean the acid spot with jewelry rouge.roy weatherford
- marietta Georgia usa
April 19, 2011
A. You can test silver with acids used for gold, but you still need to get past the silver if it is plated. (Plated will show that milky white also) I use 18K acid and test twice making sure I use heavy pressure when marking the stone.Robin H Murphy
- Palm Beach Gardens, Florida
May 3, 2011
A. There are several ways to find out if an item is silver or gold. The first destroys the item but if its scrap what the heck. It is called a fire assay. The second is a specific gravity test and takes a triple-beam scale. You may do a google search to get full instructions. We have sold test acid for years and yes some of it goes bad with time. If you have a silver scrap item, apply it direct to the item and it should turn blood red if it is 90% silver or more. The less silver content, it will either turn yellow, dark brown or if it is plated it will turn green.
They make acid that will test 10k-14k-18-k 22k and so on. I believe the 10k acid is nitric. I always file a notch in the item and apply direct when you are buying gold that goes for $1500 an ounce. You may use a stone but test needles will help as they have nearly any karat you might want to check. When buying silver or gold on ebay, make sure that they don't use a postal scale as they are not accurate. Hope this will help. This is our 50th year in the rare coin biz! Regards!
- DALLAS TEXAS
May 17, 2011
A. The first mistake is that when you test silver you DO NOT MAKE A SCRATCH on stone like you do with gold.
You need to make a small cut with a file preferably 3-square on your silver piece and put a drop of acid on this fresh cut. If this is silver there will be no reaction, but if not you should immediately see formation of green bubbles.
Aqua regia is a mixture of 75% Nitric and 25% Hydrochloric (Muriatic) acid, as correctly pointed by Chemical Engineer. However it is used for refining gold not for testing it.
- New York, New York
June 20, 2016
Ron you mention you are color blind and so acid color testing would be difficult.
I suggest www.thefisch.com they manufacture a very nice test unit that checks the round/coin It is a heavy duty plastic slab with a balance projection underneath. If the coin passes muster with weight, thickness, diameter and balance, then it is the real thing. One advantage is you can carry it in your pocket. A different fisch is needed for each type of coin.
I have no connection with thefisch company, but I do own a set.
- Hunt New York, USA
June 3, 2011
Q. If you have made a cut into the piece, why would you need the acid test? Wouldn't the cut alone visually tell you if the interior was copper or brass or??
Or is there a metal I'm unaware of that naturally appears to be silver that isn't that could be used as a core on silver plate?
- New York, New York
A. Hi, Herb.
Most silver plated flatware is nickel-silver under the silver plating, rather than copper or brass. Nickel-silver contains nickel but it does not contain any silver.
Ted Mooney, P.E.
Pine Beach, New Jersey
Striving to live "Aloha"
June 5, 2011
A. This is how I was finally able to see results with the silver tester acid from Ebay. I also bought a bottle and could not see ANY change in color when put on the stone after a rubbed the item on it. Rub the item on the stone.Then put the drop of acid on it. You will not see any change in color. But then wipe (dab)it off the stone with a WHITE piece of flat paper towel or napkin. With non silver the part of the napkin will turn blue/brown but than to clear. With silver the napkin spot will still also turn clear but there will be little red specks in the spot. Those I believe are the silver traces. This works and I have tested many different metals to be sure. Try it side by side on the napkin. One piece silver and the other non silver. You will see the difference and now know what to look for. The sellers tell you to look for a color change that never happens.They should give better instructions.Frank Smith
- Seaford, New York
June 13, 2011
Q. My question is two part, but simple. I have a sizable amount of something I believe is gold. If when I went to have it tested they used aqua regina instead of nitric acid to test would that make the metal seem like it is not gold? Secondly , How would a person tell if that happened?
My insight leaves me wondering why use an acid that is known for breakdown of gold to test gold? Nitric acid is to show karat difference. I'm thinking when I had a test of this sort done, instead of nitric, someone used aqua regia. Do you know the answer?margaret neanover
hobbyist - hamilton Ohio
June 21, 2011
Q. I recently purchased by mail order a $79.00 Gold, Silver, and Platinum testing kit with the acids...the supposed "stone" was a piece of glass that I received chipped, the Platinum Acid had been opened, and the 14K Gold testing Acid smokes whenever I open the little bottle.
Jewelry that is marked 18k gold and was previously tested as 18k-20k by Smyth Jewelers, is being dissolved on the stone by the 14k acid. Do I have a BAD kit or am I doing something wrong. They REFUSED to make good on their product or give a replacement or refund, all they say is, "...We have never ever heard of a bottle of our acid 'smoking' ", and are treating me like I am lying or weird.
I also have a 5 1/2 inch by 1/2 inch bar of something white metal colored when I put Silver acid solution directly on it nothing happens, when I scratch it on the stone and add the 14k solution it DOES NOT dissolve, can Nickel or Steel give this kind of positive or do I have Silver or Gold, oh yeah and it does not react to a rare earth magnet.CoCo Sainte-Laurent
- Baltimore, Maryland
November 7, 2011
A. E-Bay has a satisfaction guarantee, and you are not satisfied.
If you still kept the purchasing information, include it at the end of your letter. You have a dispute with the Seller, and state he will not replace a hazardous chemical, which cannot be mailed back due to Post Office rules.
E=Bay is terrific and you WILL get your money returned.
I hope this helps.
- LAKEWOOD, New Jersey
July 21, 2011
Q. Hi, I have a question about how long to leave the acid on. Is this an immediate change? I just tested my first medal - I bought it as 'test silver, no mark' . When I received it in the mail, the front indeed 'looks' like silver, but the back was just a bit too shiny and chrome-ish, so I tested the back. It was dark red, then over the course of a few seconds went to dark brown, and then started getting a creamy greenish, which I realized was the medal actually being eaten! I wiped it off and yes there is a big dull spot about 5 mm wide, but under it is a pretty creamy silver color. :) But it's a little sparkly and I know that means nothing, basically. But I'm wondering, should this have been a one-second reading? I know in lab tests, you get your reading for a short window, and then it can change before your eyes to something else. Any ideas?Megan Crisp
- Asheville, North Carolina
July 30, 2011
A. So easy...when I test for silver with my silver acid, if it's real silver, it turns bloody colored - any other color, it is not silver. Within two minutes of testing you'll have it down. I've never been wrong yet - I either scrape on the stone or directly...so easy.lisa rendon
- reno, Nevada
August 9, 2011
Q. I just bought a bottle of Griffith silver testing solution from our local jeweler that he had ordered it for me, so I know it is fresh.
I rubbed one of my wife's rings on my gold testing stone and then pulled a drop of the testing solution across the rub. the testing solution made the rub go disappear. The ring was marked "sterling". What did I do wrong, or is that the way it is suppose to work?
hobbyist - Sinton Texas
August 17, 2011 -- this entry appended to this thread by editor in lieu of spawning a duplicative thread
Q. I got ripped off at a antique store or did I? I went to test my silver purchase out at a "we buy gold" place. the guy first tested it and it was silver he said. Then he told me to go home and cut it in half so he could see if it was solid I came back and he tested it again he said nope not silver what? After ruining the piece he didn't want it. I'm confused he tested it with an acid. It made the silver black -- what does that mean?anthony salas
hobbyist - glendale, California
August 18, 2011
A. Hi, Anthony.
I wouldn't be too hard on the gold-buying shop. You didn't pay them to evaluate your find, you asked them if they were interested in buying the silver as scrap and they apparently feel that it isn't silver.
But if the antique store claimed that it was Sterling, I think they owe you.
Ted Mooney, P.E.
Pine Beach, New Jersey
Striving to live "Aloha"
August 20, 2011
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 30sec. 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.Brian Christoff
- Jacksonville, Florida
August 30, 2011
Q. I've been using the same bottle of silver testing material (nitric/muriatic acids) for about two months with success. But now, all of a sudden, everything tested tests positive for sterling ... even stainless steal flatware. I have cleaned the scratch plate with soap and water, but still get the same results. Anyone have an idea how/why this is occurring?
eBay seller - Long Beach California
December 21, 2011 -- this entry appended to this thread by editor in lieu of spawning a duplicative thread
Q. where can I purchase silver testing solutionsEvelyn Hilliard
- Middletown, Connecticut
January 12, 2012
A. Most "gold test" chemicals are in fact various strengths of "Aqua Regia",(the strength depends on the caret 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 carat 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 silverplate, you may (or likely will) end up with a permanent spot where the plating has been removed.
- Kansas City, Missouri
January 23, 2012
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.LAWRENCE GLADSDEN
- PEMBROKE PINES, Florida
January 29, 2012
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". Its very easy to do!
- weigh the silver piece on a digital scale (grams)
- 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.
Density (should be 10.49) = weight (grams) / ml of water displacement
- Concord, California
January 30, 2012
Thanks, Chuck. But I'd call this a quick "disqualifier" test to show that something is not silver, rather than a "DNA test". Because it's easy to mix together one metal that is heavier than silver with another metal that is lighter than silver, in a proportion so as to get 10.49 g/ml.
Ted Mooney, P.E.
Pine Beach, New Jersey
Striving to live "Aloha"
February 22, 2012
Q. I have a set of silver flatware that was custom made in India. It is stamped Silver, and is probably more than 50 years old. I would hate to damage it but I would like to verify if it is sterling.
Hobbyist - Los Angeles, California
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.
- Lemon Grove California
August 1, 2012
Q. Treating lower carat silver does work with acid; it always turns green even when it is silver. So if use "silver acid" what color will low carat turn? There's a lot of people mistaking low carat for plated. Can anyone clarify?Crris Ali
- Bridgeport Connecticut
November 5, 2012
Q. How to make a silver liquid from silver powder? I just want to know it sir. Please answer my question.
- Myanmar, Yangon
December 6, 2012
Q. Wondering if there is a way easy enough for a non-professional to test a sample of material claimed to be made of Rhodium plated sterling silver - if it is indeed as claimed?Jeff Ezers
- Larkspur, Colorado, USA
February 9, 2013
Q. Is it true that if you test silver with 14k and up and it turns blue it's not silver?Joseph Cancino
- Norwalk, California
March 21, 2013
Q. I have some "gold" coins I own, and a testing kit. I dropped 10k test on the coin and no reaction. Filed a grove in it and did the 10k test directly and no reaction. The 14k test dropped directly on it turns aqua blue and bubbles. From my research the 14k test tells me there is no gold, but the 10k test is telling me it is gold. Help anyone?David Herron
- Hattiesburg, Mississippi, USA
April 18, 2013
Q. Some years ago I purchased some jewelry for my family from a Jeweller I knew personally in our small Town, whose family has run a business for over 50 yrs.
One item I purchased was a heavy curb link sterling bracelet marked "ITALY 925". This item has been tucked away for years and never worn until recently!
After wearing it for approx. 3 weeks, yesterday I noticed a difference in the look of the bracelet...it appeared to have wear spots on the edges of the links and on the clasp.
Closer examination with a 10x loop proved my suspicions!
Next I tried a magnet ... nothing! Then I decided to try a drop of 67% Nitric acid on the links (without first filing a groove in it) to see how it reacted! The links turned Green immediately!
I've used nitric acid over the years to test scrap sterling silver I intended to buy and have never had any items marked .925 turn green until now!
Armed with this fact I headed to the Jeweller from whom I purchased it and spoke to him in private to discuss my concerns! He viewed the item, seen the markings and said "Who said it isn't sterling? What's Nitric Acid? I've never heard of Nitric Acid! (I found it odd that a Jeweller didn't know what Nitric Acid was ... when he told me he owned a Gold Test kit!). He said "Italian Sterling is high quality and is sometimes coated with Rhodium. Maybe it's the Rhodium wearing off! Let me polish a link then you can test it again!" I took it home tested the link he polished and sure enough it turned green again! I even took an iphone movie of it and showed him that it turned green! Now he wants his own out of Town "repairman" to test it for him, and then even suggested that upon the return of the chain from "his guy" for me to get an independent Jeweller to appraise the chain at his expense!
All of this sounds fishy to me!
Therefore my question is....Has anyone else ever experienced Rhodium wearing off of Sterling silver and reacting that way (bubbling green) when tested with Nitric acid?
- Cobourg, Ontario, Canada
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:
Blacksmith - Boone, North Carolina, USA
April 30, 2013
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,
- Canuelas, Buenos Aires, Argentina
August 17, 2013
Q. Hi, I have this sculpture of a hindu god which is gold colored outside, and inside it is of a silver color. To find out what metal it was made of I used nitric acid concentrated on the exposed silver portion: the acid was lightly creamish but after few minutes the exposed silver portion turned dark grey. When I used the acid on the gold colored part, the acid turned a light green and bubbly but did not discolor the gold portion. What metal do I asuume them to be?Nirmala raman
- Coimbatore, Tamilnadu, India
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
- Sydney NSW Australia
February 23, 2016
A. Just as a quickly.
With regard to the comment "Acids go off", can I please make a slight correction--
BUT if you combine the two and sell "pre-mixed" Aqua Regia then this DOES degrade over time as the acids react with one another. When I say "over time" within 7-10 days premix can become unsuitable for testing as a worst case and around 3-4 weeks as a best case. Beyond that and you may assume your gold is very pure and in fact it is the case that the acid is weakening.
If you can purchase the two acids on their own and simply "make your test kit with one drop Nitric and three drops hydrochloric" each time you need a few more drops of solution and your unmixed acids (if you keep them stoppered gas tight) will last indefinitely.
Do NOT store aqua regia in a gas tight bottle though as although it will outgas faster, it will then be less likely to be explode or generate other nasties - nitric oxide, chlorine, nitrosyl chloride etc.
Add this to 8 ml of distilled water and then, with care, add 22 ml of conc nitric acid. This is also called "Schweters testing solution"
File a notch in the piece to be tested.
Apply a drop of the solution you made above.
- Pure silver turns bright red
- Silver (Stirling Silver 92.5%) turns dark red
- Silver (80%) turns brown
- Silver (50%) turns green
Presence of tin or lead can make this turn yellow and nickel will make it turn blue. Palladium remains clear. Caution that an excess of copper will also make the solution go brown - so use common sense if you think the metal is 80% silver or mostly copper! Brass will make it go VERY dark brown.
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,
- Wellingborough, Northamptonshire, UK
August 21, 2013
Q. Hi. I've just had my white gold chain evaluated. The store did the acid test on the clip (so out of the way) and it came back green and bubbly. Now I've got two questions:
1. Could there be a different test required for white gold?
2. Could it be possible the clip wasn't real? (very expensive chain so would be pretty peeved)
If anyone could help that would be great as at the moment I'm a bit upset about it as my partner spent quite a bit on the chain.
- Staffordshire, United Kingdom
August 29, 2013
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.
- Canuelas, Buenos Aires, Argentina
September 3, 2013
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.
Feather Hollow Eng.
April 23, 2014
Q. I tested a yellow gold pin. When I scratched it on the stone it was a silver color and did not dissolve with 14k acid test. Is it white gold under a layer of yellow gold?Joseph Cancino
- Lake Eksinore, California
February 28, 2015
Q. I have this silver creamer dish. I made a deep groove in it with a file. I put my silver acid tester on it and it turned a creamy color then to black. What does that mean?Tarah joans
- Kelso, Washington Usa
July 2, 2015
Q. What does it mean if it does not bubble green, but solution turns blackish?
My solution is good - I tested a piece of 950 - bright red.
OLD TO NEW - Guntersville, Alabama, USA
August 19, 2015
Q. Let's keep it simple. Bought silver testing bottle on ebay and it worked on Monday perfectly.
Then 3 days later tried on another pile of silver purchased and EVERYTHING turned light green!
Retested on items that stayed dark red and they also turned green.
Do you need to order a new bottle every time you open one ?
- Hilton Head Island, South Carolina
August 22, 2016
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 weakish, 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 silverplate (!)...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, 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.
- Yonkers New York USA
January 13, 2016
Q. Here's a different situation.
I have been employed as a precious metals buyer and have considerable experience with testing solutions and technique. As a lapidary I have an abundance of specimens picked up from various places that are unidentified. But that doesn't stop me from slicing them up and giving them a polish. I recently slabbed up a couple "quartz-y" rocks and noticed patches of gold metallic material. Having nothing but silver testing solution on hand I put a drop on one of these patches. No effect on most of the patch, with the exception of very small pin points of blood red indicating high grade silver. My question is: is this a reasonable test that is determining that these patches are indeed gold with trace amounts of silver? No other part of the matrix/quartz material reacted in any way, and after rinsing you couldn't tell the acid had ever been there. Thanks for any response.
- Grand Rapids, Michigan, USA
January 8, 2017
Q. Can red gold be tested with the same acids that yellow gold is tested with?If yes what colour would the acid make on the red gold?Millecent Skippers
- South Africa (Cape Town)
Red to black then greyAugust 28, 2018
Q. I tested some sterling sheets that I bought. The filed notch first turned dark red, then black and as the acid dripped across the piece of silver, it was black then left a grey mark on the silver.
Question: is this normal or should it stay red indefinitely?
hobbyist - Sarasota, Florida
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