Juices with an acidic base, such as lemon, dissolve the tarnish, which is copper oxide, from a dull penny. Other substances, such as Coke, Pepsi and vinegar, also make a penny shiny again.Continue Reading
Adding salt to these substances is more effective as the salt speeds up the acidic effect. Without the salt, lemon still cleans but not as quickly. However, salt does not clean the penny on its own.
Pennies that were made prior to 1982 were solid copper. After this time, they are made of zinc with a copper plating. Zinc can erode if it comes in contact with acid.Learn more about Coins & Currency