Baking soda, salt and aluminum foil. Use one sheet of aluminum foil, shiny side up. Lay all of your darkened costume jewelry on the foil. Mix one tablespoon salt and one tablespoon of baking soda and mix with one cup warm water. Pour into the dish. The mixture will create a chemical reaction with the foil and bubble as it cleans the jewelry. Rinse with cool water and dry.
Toothpaste. Squeeze a small amount of toothpaste on to your tarnished jewelry. Once the jewelry has a thin coating, brush clean working into the tarnish with the old toothbrush. Always make sure your jewelry is dry when you store it after cleaning.