How to Find out the Purity of Your Silver

Cover your work area with newspaper because the acids used can potentially damage your work surface. Using the sharp file, file a small, deep groove into a discrete location on the item, being careful not to damage or disfigure the item. Shallow grooves cannot be used as many items are silver plated, and a surface groove may not give a true reading of the silver content of an item. Or, if you are confident your item is not silver plated, firmly scratch an edge of the item with a test stone, being careful not to damage the item. A streak on the test stone will be visible if this is done correctly.

Place a single drop of silver test acid into the groove and wait for color change to occur. Or, place a drop of the test acid onto the streak on your test stone and look for color changes. You can use the silver test acid directly on your silver item without filing a groove or using a test stone; however, be aware that the acid can stain an item and dull its polishing. All acid testing, no matter how precise, is likely to leave a mark on the item. For this reason it is not advisable to acid test silver coins or small items of silver jewelry as their value is likely to be affected.

Look closely at your item. If the acid turns a creamy color, the item is 90 to 100 percent pure silver. If it turns a gray color, it is 70 to 90 percent pure silver. Light green indicates 65 to 75 percent pure silver, and if the acid turns dark green, this shows that your item is silver plated. The dark green color will be caused by the high copper content common to many low-grade silver alloys.