Ethnic Jewels

An appreciation of ethnic jewellery and adornment

A few people have asked me how I test silver content and so I will share what I do.  I want to start with a few caveats. 

First, you can harm a piece of silver with testing.  You are going to use a strong acid!  So practice first and be sure you really want or need to know the approximate silver content. 

Second, I WELCOME CORRECTIONS and additions.  I am just a curious amateur.  Most silver testing instructions recommend scratching or filing a piece which I reject for obvious reasons.  This is what I pieced together in my ignorance, and in making mistakes and correcting them.  

Third, I am convinced the real way to test silver content in ethnic jewelry is with an XRF (x-ray) analyzer which will give a complete picture of the metal content.  Some shops which deal in large volumes of precious metals have them, for example a coin shop in the San Francisco Bay has one.  Unfortunately none do in my area.  :(  If you have a shop near you with an XRF analyzer it would be well worth doing some testing and writing an article about the experience, IMO.

   

Materials needed:

  • Nitric acid which has been formulated for silver testing
  • Coins of known silver % for comparison, if you want to be precise.  (Ex, if you have a Thaler then you have .830 silver)
  • Bright light
  • Magnifying glass if needed
  • A dry white paper
  • A wet cloth
  • A plastic embroidery needle or other fine-pointed, non-reactive instrument you will use to pick up a drop of acid
  • A porcelain or plasic (non-reactive) dish
  • If desired, a VERY FINE sandpaper to remove the mark after you have tested.  I use a 1 micron or 3 micron polishing paper available on Amazon.com

 

Procedure: 

  • First, practice on the coins!  You will do this for two reasons. 1) to make sure you are comfortable with the whole procedure since you want to be precise and quick to avoid leaving a large mark or having acid run into a hole, or running into coral or amber… not good!  2) to calibrate your particular acid and become familiar with what color red it is going to turn with .700 silver, .800 silver, sterling, and higher-than-sterling.
  • Take the acid and put a large drop on a porcelain or plastic (non reactive) dish.
  • Lay out the piece to be tested, the dry white paper (like kitchen paper), and the wet cloth under good light.
  • Select the spot to test on the piece.  I like to choose parts that are unobtrustive and also worn, because a worn spot means the piece is not silver plated.  Sometimes you can just tell it is not plated because of the amount of wear with no difference in the metal, in that case just pick an unobtrusive spot.
  • Hold the silver piece so that the unobtrusive spot is flat.  The acid can run, particular after it starts reacting.
  • Take your plastic needle and dip the end in your spot of acid on the dish.  Get a small amount of acid on the needle. 
  • Touch the needle to the spot to be tested.  Observe the color it turns, if it turns a variation of red or brown, wipe the spot with the dry white paper.  Set the dry paper aside.  Now wipe the spot with the wet cloth so you remove the acid.  It can turn red or brown in 10 seconds.
  • If it does not turn red, allow the acid to sit there for 30 seconds, and then wipe it with the dry white paper and then the wet cloth.
  • It is possible you will see it turn red, and then quickly start to turn a grey/blue color.  This likely means the piece is plated.

 

Now you will read the color of the spot you have made on the dry, white paper:

  • If the spot on the paper is brown through bright pinkish red it is somewhere between 70% and 100% silver.  The redder it turns, the higher the silver content.  With my acid (you should calibrate yours with the coins), higher than sterling is pink-red, sterling is blood-red, 800+ is red-brown, and 700+ is brown-red.  I have never had .600 silver to test.
  • If the spot turns pale green, it is about 50% silver.  
  • If the spot turns blue or a different color, the silver content is too low to test.  This does NOT mean there is no silver content, I have tested coins that have 20% silver content and the result was pale blue. 

 

 How to remove the spot on the silver:

  •  Acid testing leaves a spot on the silver which won't come off with a polishing cloth.  It will however come off with the 1 or 3 micron polishing paper which will not harm the finish of the piece.

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Comment by Cordelia Donohoe on October 6, 2015 at 0:01

Yes, I have found the Caratest amber fluid to be unreliable for testing 60% silver and under. Its available to buy on Ebay quite easily.  I did not think green was an indicator of anything, so that is interesting to read. My 60% pieces turned greenish and it was only the x ray that showed me results I could trust. Always keep the acid in the fridge it lasts longer, otherwise it goes very quickly. I find acid on silver in 70% and upwards shows almost immediately. I dont use a touchstone but it seems good advice to do so.

Comment by Charlotte Dakin-Norris on June 18, 2015 at 7:44

Dear Lynn, thank you for finding them; they were not showing up for me when I was trying to find Schwerter's before! The US based firms that stock it won't post to the UK but I am hopeful that it can be sent without problems from Ireland. We can compare our findings! This is a link to a page which mentions results of using the solution with different silver alloys (as well as gold):

http://www.sciencecompany.com/How-to-Test-Gold-Silver-and-Other-Pre...

Comment by Lynn Ardent on June 17, 2015 at 17:53

Dear Charlotte, thank you for your comment and also for alerting me to the Schwerter's solution.  I have never heard of it, but after your comment I found it on eBay US and purchased a bottle which I will try and see if it detects lower silver concentrations.  I noticed there is a seller based in Ireland also selling it on ebay US in case that helps you. 

Comment by Charlotte Dakin-Norris on June 17, 2015 at 16:10

Hi Lynn,

Thank you so much for taking the time to write this guide - it is very interesting! In the UK we have access to a couple of acid tests for silver - one is the Troy Test for Silver which is an amber fluid containing nitric acid, and Caratest produce a clear acid which detects silver and gold (9ct or above) - I don't know what this clear fluid is exactly, but it must contain some Nitric acid.  The results of my testing so far with the amber fluid is that it only detects silver of .800 or above; it does not turn pale green on 50% silver...it just stays amber. The Caratest fizzes green if it touches a copper alloy, so it is difficult to tell what the percentage of silver is! I think that the amber fluid you are using must be a different formulation to the ones that I have tried. 

There is also Schwerter's testing solution which is difficult to source in the UK, but it is a mixture of Nitric acid and Potassium Dichromate. This can detect silver at 50% and above and I am keen to try it. I will let you know how I get on when I get some.

I have not had much joy using a touchstone so far, so I follow the same method as you!

Comment by Lynn Ardent on June 17, 2015 at 15:05

Hi Alaa, I personally don't scratch because I don't want to put something that I can't remove, and I don't know how to remove scratches.  But a few mm of acid stain (using a plastic pin to place it so it is really small)  can easily be removed with a 1 or 3 micron polishing paper.  Here is the paper I use:    

http://www.amazon.com/Zona-37-948-Polishing-11-Inch-Assortment/dp/B...

Comment by Alaa eddine SAGID on June 17, 2015 at 14:59

don't you use a touchstone on which you scratch a hidden part of the piece that way you don't risk using the acid directly on the piece but on the marks it left on the stone ?

This is how i practice my testings....and gosh, how many surprises i got!! :-(

Comment by Lynn Ardent on June 10, 2015 at 13:40

You are most welcome Betty.  If I were you I would buy it on eBay US and have it shipped.  My bottle just says something like "silver test solution" on the label and hence I doubt would concern curious customs workers..  the bottle you want will have an orange solution in it.

Comment by Betty on June 10, 2015 at 12:33

Very, very helpful Lynn! Thanks a lot.

Unfortunately in Germany you cannot buy Nitric acid formulated for silver testing freely (unless you are a jeweller or deal professionally with precious metals). But I am sure there  must be ways ...

I have so far used a 2-phase-silver tester that is quite unreliable and complicated to use. Or else I go to the jeweller who also repairs things for me and kindly tests my pieces free of charge.

But I would also really like to try your method which sounds well-designed. Again, many thanks for sharing it with us!

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Created by Cordelia Donohoe Apr 10, 2017 at 4:03pm. Last updated by Cordelia Donohoe Apr 17.

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