If you have dirty coins, Rules # 1 through 100 are DO NOT TRY TO CLEAN THEM AT HOME. Any household chemicals you might use will damage the coin itself and significantly reduce its value. The most you should do is to dab a dirty coin with some distilled water and a soft cloth. If you have a coin known to be valuable that is encrusted in dirt or other crud, youll need to contact a coin dealer about finding a company that specializes in cleaning. They have the right tools and techniques to avoid damage. Such a firm was used to remove 150 years of ocean grot from the coins found on the S.S. Pacific, for example.