Loose change, often filled with pennies, can be cleaned using a mixture of water, salt, and a mild acid such as vinegar or lemon juice. It’s important to ensure that collectible coins are not accidentally damaged during cleaning. Pennies made after 1982 may contain mostly zinc and require a different cleaning method.
Many people have a jar or other container of loose change in their house, and it’s often filled with pennies. These coins wear and tarnish over time, and there are various methods for cleaning them, but most use the same few simple principles of chemistry. One of the simplest and most common ways to clean pennies is to wash them in a mixture of water, salt and a mild acid.
The first thing to do in cleaning these coins is to be reasonably sure that none of them are potential collector’s items. If the change came from buying a cup of coffee in the morning or from a vending machine, then the chance that they are collectible is slim, but it still helps to be safe. Removing tarnish from a collectible coin can accidentally destroy its value, so it’s best to set aside anything you’re not sure about.
The materials needed to clean the dimes are very simple. A shallow plastic or glass bowl should be filled halfway with water. Add 1 mL of white vinegar and 4 teaspoons (60 g) of table salt to the water and stir until the salt dissolves. Put 1 to 6 cents in the bowl for about five minutes. It’s a good idea to mix them once or twice during this time. After five minutes, the coins can be rinsed and dried and will retain their shine for a while.
Pennies become dull and blacken over time due to the copper that is used in their composition. Copper slowly reacts with oxygen in the air to form copper oxide, which has a dull, greenish color, and this is what people see as tarnish on copper pennies. When cents are washed in a mixture of vinegar and salt, the acetic acid in the vinegar is able to dissolve the copper oxide, leaving the coins shiny and clean. You can use lemon juice in place of vinegar, due to the high acid concentration in lemons.
Ketchup and hot sauce can also be used instead of vinegar, as both contain acids and salt. The presence of salt is more important, from a chemical point of view, than the type of acid used. If you want to clean pennies minted after 1982, keep in mind that around this time, pennies started to be made mostly of zinc, rather than copper, due to the rising price of the metal.
Zinc can be degraded more easily by an acidic solution than copper. If this is a problem, the pennies can be cleaned with a light abrasion. Rubbing a pencil eraser on a penny will remove most of the tarnish, though not as much as salt and vinegar.
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