Cleaning Coins
If you think your coin may be valuable or if you don't know the value of the coin, do not clean the coin.
Most coin collectors do not want clean coins and want the coins "as is". Over time coins develop different tones and coin collectors do not want the coin tarnished by removing natural luster. Coin collectors will want a fully bright coin over a dull coin or toned coin, but they will want a toned coin much more than a dull or cleaned coin.
For coins that are cheap that you want to brighten up, hand soap and distilled water is your safest bet. Use either your fingers or an extra soft toothbrush and rub the coin in a circular motion. Cupping the coin in the palm of your hand is an effective way to hold the coin while cleaning the coin with a toothbrush.
Cleaning Silver Coins
As with other coins, do not clean the coin if it is valuable.
A neat trick to clean silver coins is to cut out a few 2 inch by 2 inch (or so) squares of aluminum foil and put a little bit of baking soda or baking powder onto the middle of the aluminum foil square. Next put your silver coin onto the powder and put more powder on top of it. Be sure to cover the coin. Fold up the foil around the coin, but be sure to allow some "breathing" room.
Get out a coffee mug and fill it with hot water. Microwave it for a minute or so to get it really hot. Drop your foil covered coins into the hot water and wait a few minutes, or until you don't see anymore bubbles coming from the water. Fish out your coins with a plastic spoon. Unwrap them and wipe them down with a cloth. Be sure to fully dry the coins before putting them into a holder.
