When exposed to the elements, any copper without a protective sealant eventually develops a green patina. Wearing a copper ring or even handling copper may cause a similar green hue on your hand, but don't worry; it's not a permanent stain. In most cases, simply washing your hands with soap and water removes the discoloration.
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Why Copper Turns Green
Over time, especially on outdoor objects, copper turns a bluish green, as evidenced by looking at the Statue of Liberty. When moisture, oxygen, and other elements in the air reach copper, a slow reaction occurs, eventually creating a patina over the copper's surface. The patina in this case is copper chloride, a greenish or turquoise substance that's also called verdigris, from an old French term meaning the "green of Greece."
Wearing copper jewelry may create a similar reaction between the copper, the air, and the moisture and oils in your skin. This is why you may notice a greenish hue on your skin without seeing much, if any of it, on the metal. Even copper jewelry you don't wear eventually develops a patina if exposed to air, as will copper countertops or copper pots and pans. Other metals that contain copper, such as bronze, develop a similar patina.
Removing Green From Your Hands
Wash your hands thoroughly with soap and water, focusing on the area that appears somewhat green. Rinse and check your hands again. If you still see any green on your skin, use a mild abrasive, such as a sprinkle of baking soda, on your hands with more soap and water. Use a washcloth to gently scrub your skin.
If you've worn the same copper item for years, such as a ring, and the green mark on your skin doesn't come off easily, it will fade over time and over several washings. In a pinch, heavy-duty hand cleaners such as those containing pumice used in automotive repair shops also come in handy for removing tough skin stains.
Preventing Green Skin
The best way to keep copper items from turning your skin green is to ensure the copper is clean and free from patina when you handle it. Cleaning the copper regularly is also a good idea if you want it to maintain its original color. Wipe the copper frequently with a nonabrasive, soft cloth, such as microfiber or cotton.
If the copper is already greenish in some areas, remove the green by soaking the affected part in a little lemon juice for about 10 minutes. Rub the copper with a soft, damp cloth with a little salt on it as an abrasive. Lemon juice works well for removing patina and tarnish. Do not use abrasive cleaners, such as kitchen cleanser, as these could harm the copper. Products designed specifically for cleaning and polishing copper also help your copper items maintain their original appearance.
Proper Copper Storage
Store small items such as old copper coins or pieces of copper jewelry in airtight packaging, such as zippered bags or another airtight container. If you've recently worn or handled the copper piece, wipe it off with a microfiber cloth to ensure it's completely dry. Feel free to keep your prized copper pieces in soft jewelry-storage bags; then put those in zipper-seal plastic bags for complete protection. Airtight packaging won't prevent your copper items from developing a patina once you remove the materials from the package; it simply prevents the items from changing colors while you're not using them. In other words, it prolongs their original color and delays the patina process.