You will need
- - solution of ammonia;
- - a drug called Trilon-B;
- - mineral oil;
- - toothpaste;
- - cleaner (e.g., Drano);
- - canvas.
If you find old copper coins, covered with an even layer of patina (greenish patina formed by oxidation of copper), it is possible you don't clean it because the patina is a natural protection of the metal from the environment, and the price of the coins from coin collectors not affected. From the patina can be removed by placing the coin in a 10% solution of ammonia. Thus it is necessary to watch, that the coin was completely hidden solution, as the contact of ammonia with air can damage the metal. After the green coating will change color to white, the coin can be dipped in vegetable oil and wipe with a dry cloth.
Blackened copper coin or piece of bronze can be cleaned with a solution of the drug under the name of Trilon-B (disodium salt of ethylenediaminetetraacetic acid). Unlike acids, it affects only the oxides without damaging the metal itself. Depending on the state of the object the validity period can vary from several minutes up to 5-7 hours. After treatment with Trilon-B coin should be rinsed with clean water and wipe.
One of the most humane ways to clean copper or bronze is to boil it in paraffin oil, which you can buy at the pharmacy. Cleaning is enough to hold a coin in boiling oil for 10-15 minutes. Be careful, get a coin only after the oil has cooled sufficiently. After this bathing, the coin a few minutes to boil with a washing powder or detergent to get rid of oily residue.
The option recommended by restorers for heavily soiled coin: hold the coin for 1 minute in the cleaning solution, and then boil the soap flakes with water and place coins in a soapy solution for 2-4 weeks, periodically removing them and cleaning with a toothbrush. At the end of the coins should be boiled in sunflower oil for about 10 minutes and wipe with a linen cloth.
When used for cleaning bronze of ammonia will darken metal. In order to return the product the original color, rinse it with warm water and toothpaste.
Do not clean coins strong acids as they can damage the coins.