Creating verdigris or a patina on copper coins is easy to achieve. Many coin collector hobbyists choose to create this green pigment on their coins to give them an aged appearance. There are several methods to achieve a patina on copper. Below are two methods. Both will result in a beautiful greenish-blue patina. You can repeat whichever method you choose until the desired effect is created.
Wipe off your copper coin so that it is dry.
Pour a small amount of vinegar into a plastic dish.
Pick up the coin with a pair of tweezers and hold it in one hand.
Dip the cotton swab into the vinegar and dab it onto the copper coin. Flip the coin over and dab the other side.
Set the coin on a dry surface. As it dries, the patina will become visible. Repeat the procedure if a darker patina is desired.
Mix one part sulphur powder with five parts petroleum jelly. Stir well until all of the powder is mixed into an even paste.
Coat both sides of the copper coin with a thin film of the sulphur-jelly mixture.
Leave the coin to sit until the desired effects of patina tarnish are achieved. This will happen gradually over time.
Store the remaining sulphur mixture in a glass jar for further applications if desired.
Remove the paste from the tarnished coin using a cotton swab and gasoline. This will keep the patina and take off excess petroleum jelly.