How to Clean a Coin Supply

Check the value of the coin prior to cleaning. If the coin is valuable, take it to a professional for an opinion on whether to clean it or not. The loss in value can be as much as 90 percent.

Wash the coin using cold water. Use as high a water pressure as possible to remove the dirt on the surface of the coin. Hold the coin at the edge while washing to prevent damaging the coin's surface.

Place the coin in olive oil and soak it if washing did not result in fully cleaning it. Soaking time may vary according to the amount of grime present, with soaking times extending up to two weeks. Soak gold coins in hot soapy water, but use distilled water from bronze coins to keep the minerals present in tap water from tarnishing the surface further. Soak silver coins in lemon juice for five minutes to remove grime. Remove the coins when the soaking liquid discolors due to the release of dirt from the coin's surface.

Rinse the soaking liquid from the coins immediately using warm water.

Brush the coin with a soft toothbrush if dirt remains, rinsing both the coin and brush often to avoid a build-up of abrasives.

Dry the coin by patting the surface with a lint-free cloth to remove the majority of the water. Lay the coin on a clean cloth to finish drying.

Examine the coin for cleanliness. Remove specks of dirt that remain using the tip of a toothpick. Pry away the dirt with the toothpick, making sure not to scratch the coin.