Knowing whether or not your piece of jewelry is platinum and the purity used to make the piece of jewelry is very important when you are getting the piece appraised or attempting the sell it. The most reliable method for testing platinum is with a kit that includes a black testing stone or glass and a testing solution for platinum. Most kits will also include testing solution for 10-carat, 12-carat, 14-carat and 18-carat gold jewelry. Typically, platinum test acid is an additional solution that may also be used to test 22-carat gold jewelry. The jewelry will not be harmed in the testing process as the testing requires a very small metal deposit.
Run a sharp edge of the jewelry across the black stone. Apply enough pressure to create a 1-inch bright white line across the black stone.
Release one drop of the testing solution centered on the white line. Apply the drop at one end of the white line in order to perform subsequent tests without having to scratch another metal deposit.
Wait at least 3 minutes. Watch to see if the line disappears. If the line completely disappears, the metal you are working with is not platinum. In this case, the metal may be white gold less than 22-carat, nickel, palladium, silver or a mixture of metals. If the line changes colors, the metal in the jewelry may be an alloy and not completely pure.