As a general rule about Cleanning coins!,

Coins should not be cleaned at all as doing so may end up ruining the coin's numismatic value, As a collector I will pay a considerable premium over the catalogue value for a coin featuring an attractive and original patina. The wisest course is to leave your coin collection untouched and stored in the proper holders.

The reason that cleaning coins is rarely a good idea is that 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.

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.

If you decide to clean your coins, here are some pointers to keep in mind to avoid or minimize the chances of damaging them.

Soaking a coin in olive oil or mild soapy water is another method that can often safely remove dirt or other substances adhering to a coin.

Always use non-abrasive cleaners such as rubbing alcohol or olive oil to clean coins. Commercial jewelry and metal polishes are usually too harsh. Never, for example use silver tarnish remover to clean silver coins as it will adversely affect a coin's natural toning.

Always rinse the coins with distilled water after cleaning. Tap water should not be used as it contains minerals which may create spots on the surface of a coin. Let coin air-dry after cleaning - never rub a coin dry.

Tarnished coins should only be cleaned (if at all) by a professional using a process known as "dripping". Do not attempt this process yourself.

Some collectors like to use baking soda as a cleaning method to make a worn coin look shiny and new. This is not recommended as it will generally ruin the numismatic value of a coin.

Never clean touch or rub the surface of any Proof coin. If there is dust on the coin simply blow the dust away gently.

Finally it should be noted that, The best advice we can give for most people about cleaning coins is...
don't!.

Regards
Charlie
Cyber Coins & Banknotes