Testing sterling silver

Recently had a question which I though would be worth sharing:

Hi, I have a question on how to test for silver. I don't know if after rubbing on touchstone and appling acid, does the mark turn a special color?

This was my reply which may help those with a similar problem....

Firstly it is important to realise that you do NOT use a touchstone for Silver.
You should test the article itself.

Lightly scratch or scuff a small spot which is not seen (like underneath a silver teapot or inside a ring band etc) and apply Nitric Acid to the spot.

If it turns a cloudy grey color it is Sterling Silver. If it turns black it is Coin Silver. What you don't want is for it to turn green which indicates it is plated.

You must ensure you make the scratch deep enough to go beneath any plating though, else it won't react as it has to reach any base metal underneath. This can be a little unsightly so make sure it is in an unobtrusive area.

Be very careful with Nitric Acid too...

Hope this helps. I am sure there is some useful information on the Antique Jewery of the 20th Century website.