DO NOT CLEAN your coins – cleaning coins results in altering their original surfaces, which in turn devalues them. Even if they appear in need of sprucing up to sell for a higher value, resist cleaning them. Cleaning is apt to alter a coin’s surface or toning in an undesirable manner (such as leaving small “pock marks”, spots or scratches on the coin’s surface) unless great care is taken and the proper cleaning method is selected.
As a general rule, coins should not be cleaned at all as doing so may end up ruining the coin’s numismatic value. The wisest course is to leave your coin collection untouched and stored in the proper holders.
It is a good idea to consult a coin dealer or other coin expert to assist you in deciding whether cleaning a particular coin is a good idea. When in doubt do not clean a coin.