Sterling silver jewelry can be identified by a "925" marking. This marking refers to the 92.5 percent pure silver composition. Usually the other 7.5 percent is added copper to give strength to the metal. While pure silver is not very reactive and does not tarnish easily, the addition of copper makes sterling silver prone to tarnish. Tarnishing can be prevented by storing your sterling silver jewelry in an airtight plastic bag, but when tarnish does occur, you can return the sheen to your jewelry with a few simple steps.
Line a pan with a double layer of aluminum foil. Gently place your tarnished sterling silver jewelry on the foil so that the pieces are not touching.
Fill a pot about halfway with water and bring the water to a boil. Immediately remove the pot from the heat and add 1/2 cup of baking soda.
Pour the hot water and baking soda into the pan with the tarnished silver jewelry until each piece is covered completely.
Allow the silver jewelry to soak for several minutes. If the pieces are still tarnished after 10 minutes, reheat the water and baking soda and soak your jewelry again until the tarnish disappears completely.
Rinse your sterling silver jewelry thoroughly and dry with a silver polishing cloth. Store your newly cleaned jewelry in a dry place free from dust.