Almost all people who are fond of numismatics are faced with such an unpleasant phenomenon as oxidation and aging of coins. During storage, dirt and moisture accumulate on the surface of the coin, which leads to the loss of its presentation.
From time to time, it is necessary to clean the coins from dirt - for this it is enough to wash each coin in warm soapy water using a soft brush. Removing oxidation marks from a coin is a little more difficult than just washing off the dirt. When removing oxidation, the nature of the metal from which the coin is made must be taken into account. Just rinse gold coins thoroughly in warm water. High-quality silver is purified with a special agent called Silbertuschbader. In its absence, you can use a solution of ammonia. Low-purity silver can be effectively cleaned by immersing the coin in lemon juice for three to four hours. Another simple and quick way to clean silver is to wipe coins with wet baking soda gruel. You can clean copper coins with a 10% acetic acid solution (however, ordinary table vinegar will also work). It is necessary to immerse the copper coin in the solution for a few minutes (if the coin is not very strongly oxidized) or for several hours (if the signs of oxidation are pronounced). If a green film has formed on the coin, which numismatists usually call "copperhead" (oxide based on copper acetate), it is better to give it to a specialist - it is almost impossible to clean the copperhead on your own. But it is not recommended to remove the noble copper patina - it does not spoil the coin, on the contrary, it helps it to last longer. Many numismatists consider the presence of a patina on a coin as evidence of its authenticity. Iron and zinc coins are cleaned very carefully using a dilute hydrochloric acid rinse. Rust or deposits from such coins should be removed with the tip of a scalpel or knife, or in extreme cases with a brass wire brush. When cleaning a coin with hydrochloric acid, try to make the solution as less concentrated as possible, as too concentrated a solution can damage the design on the coin. Coins made of aluminum, tin or lead should not be cleaned with harsh chemicals. To clean them, cloth or felt is used, and small dirt is removed with a so-called "glass brush". After cleaning, coins made of any metal are recommended to be washed with copious amounts of warm and then cold water, and wiped dry.
