How to easily clean your coins with CLR You can use a plastic cup for the container that you clean the coins in. Add 1/4 cup of CLR and 1/4 cup of water to the cup. Let the coin soak in the cup for about 30 minutes. If the mixture doesn't work on the coin you can add less water so that the CLR is more concentrated. Pour the CLR mixture out of the cup into another cup leaving the coin in the original cup. Rinse the coin off with water. The water should rinse off a lot of the corrosion that was loosened by the CLR mixture. You will have to flip the coin over in the solution so that the CLR can get to both sides of the coin. This is a very easy way to clean old coins that you find with your metal detector.