Out of all coins, older ones are usually the rarest, yet the dirtiest. Some coins have greater value when left alone, and others you should clean before trying to sell to collectors. If the cleaning process damages the coin, the coin's value may decrease by up to 90 per cent. On the other hand, cleaning your old coin properly could improve your coin's appearance, increasing its value. If you decide to clean your coin, you should always use a cleaning method that is the least damaging to prevent altering the coin's value negatively.
Take your old coin to a reputable coin dealer and have it inspected. He should tell you the coin's rarity, worth, and whether it's authentic. Ask him if cleaning the coin would increase or decrease its value. Keep all this information in mind and determine if cleaning it would be in your best interest. Use a coin pricing guide or go online to find the price if there isn't a local dealer.
Use soap and water to wash your hands before handling your old coin. Foreign material such as dirt from your hands could decrease the coin's value. Block the drain or garbage disposal in case you accidentally drop the coin into the sink. Use your thumb and index finger to hold the coin by its edge and let hot water run over it. After a few minutes, flip the coin over and repeat the process.
Pour two cups of warm purified water into a plastic or glass container. Add one tablespoon of mild dish detergent into the container and mix gently. Place the coin inside and wait until it's reasonably clean. Depending on the coin's original condition, the cleaning process may take two hours to two weeks.
Run the coin under hot water again. If the coin still isn't as clean as you'd like, get a soft bristle toothbrush. Run the toothbrush under water to make the bristles softer. Use the toothbrush lightly to clean the coin.
Pour distilled water into a glass or plastic container. Place the coin into the container for a finishing rinse. Remove the coin, place it on a cotton towel and let it air dry. Store the old coin properly in a small envelope, plastic bag or coin album.
Use your fingertips to clean the old coin instead if you're wary about using a toothbrush. Do so carefully to ensure you don't damage the coin.