Testing silver at home for authenticity and purity is easy. Silver is considered a precious metal and luckily for consumers, nearly all consumer items that are silver are marked sterling silver. Bullion silver bars are typically .999 pure silver, meaning other metals have not been used to alloy the silver. A simple acid test can reveal if an item is pure silver or if it is plated.
Look for markings on the piece. Most consumer silver--antiques, tea services, jewellery and the like--is typically marked "Sterling" or ".925," which references that it is 92.5 per cent silver and 7.5 per cent other metals.
Scratch the surface. In a protected area that is not readily visible, use a pin to make a scratch. If you can see an underlying base metal of copper, than the item is plated and further inquiries are rendered unnecessary. If it appears to be silver, an acid test is most effective when applied to a fresh, small filed cut in a protected area.
Use a silver testing acid. Silver-plated items, or low-quality silver, will turn green when a drop of nitric acid is applied to the surface. This indicates high copper content of the underlying base metal. Sterling silver will turn a creamy colour. To use a testing acid, simply squeeze a drop onto the cut you made, and it will react instantly. The dropper will be included in the testing kit. You can purchase silver testing acid from most jewellery supply shops.
Do not attempt to scratch or place acid on rare coins, as doing so may seriously diminish their value.
Use chemicals in a well-ventilated area.