Occasionally, copper jewelry or the skin of its wearer can turn green. This happens when the metal interacts with sweat and is referred to as copper chelates. The chelates assimilate to the body and are absorbed, and many wearers expect this to happen as proof that the copper is working with their body. Green coloring on the skin comes off with soap and water, and polishing copper jewelry is as easy as finding an acidic item in the kitchen. Lemon and ketchup are both excellent for cleaning copper jewelry. Simply place the piece of jewelry in a small bowl and cover with your choice of cleaner. Let it soak for no longer than 20 minutes. If necessary, use a soft toothbrush to reach into crevices on the jewelry. Use mild soap and water to wash the acidic cleaner off the jewelry and pat dry with a soft cloth. The piece of copper jewelry should regain its shine and look new again.