HOW TO CLEAN COINS
Collectors should never clean coins that have a collectible value greater than the value of the metal or alloy, because cleaning can cause microscopic abrasions on the coins and reduces their value.
Experts call the tarnish on valuable coins "Patina" or "Toning." buyers often clean circulated junk silver coins because the coins are worth as much as the value of silver content in them.
Here are some ways to clean junk silver coins. Clean the tarnish lay a square piece of aluminum foil at the bottom of a stainless steel pan. Fill the pan with a few inches of water, and bring it to a boil. Turn off the burner when the water is boiling hot. Alternatively, lay aluminum foil in a plastic or any non-metallic container and pour boiling water into it. Add half a cup of baking soda and a tablespoon of salt into the pan or container.
Put the coins into this solution on the foil in a single layer. All the tarnish from the coins disappears after the baking soda causes a chemical reaction that transfers the tarnish from the coin to the aluminum foil. Clean the grime take coins with grime deposits to the sink. Scrub each coin individually under the faucet with baking soda and water. Use thumb and fingers to rub the coins with baking soda paste. Use an old toothbrush with soft bristles to clear grime from the nooks. Baking soda is a very soft abrasive and causes no damage to the coins. Dry the coins with a towel or a soft jeweler's cloth. Clean stubborn stains place the coins in a jar of liquid silver cleaner for fifteen minutes.
Read instructions on the silver cleaner container and follow the time accordingly. Some collectors place the coins in lemon juice for an hour and rub them with fingers and a towel afterwards to clear the stains.