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.
- 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
- 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: