To perform a silver acid test, you need a bottle of silver testing acid, a rubbing stone and the objects to be tested. You can buy an acid test kit that includes 6 bottles of acid for testing gold, silver and platinum and a rubbing stone for around $14.00.
You begin the test by taking the object to be tested and rubbing it on the stone such that the object leaves a 1” long mark approximately ¼” wide on the stone. You then apply a drop of the acid on the mark and watch for the acid to turn a color from reacting with the metal. The following is a list of colors and what the approximate purity of the silver that each color represents:
Bright red .999 Silver
Dark red .925 Silver
Brown .80 Silver
Green .50 Silver
Aqua No Silver
Unlike the gold acid test which requires different acids to test for the different purities, the silver test only requires 1 bottle.
NOTE: The acid is a caustic mixture of muriatic acid and sulfuric acid and will burn the skin if it comes in contact with it. Do NOT leave the acid where it is accessible by children.