To turn copper green, create a verdigris paina by rubbing the metal with a vinegar and salt solution. Before you begin, gather some steel wool, a bowl, paper towels, dish soap, baking soda and a finishing wax or lacquer.
Clean the copper thoroughly
Use the paper towels and dish soap to clean the metal to remove oil and grime. Sprinkle both sides of the metal with baking soda, and rub the copper with the steel wool in the direction of the grain. Dry the metal with paper towels.
Mix the patina solution
In a bowl that is large enough to submerse the metal, combine equal parts of vinegar and salt. Use enough vinegar to cover the copper completely. Stir the mixture until the salt dissolves. Place the copper in the bowl, and let it sit for at least 30 minutes. If necessary, turn the metal over to ensure an even coating.
Wait for the patina to develop
After removing the copper from the solution, let it air dry. As it dries, the patina slowly covers the metal. Allow it to sit for a few hours to a few days until it achieves the desired color. Rinse and dry the metal. Since the patina can be crumbly, apply a sealant to protect the final patina.