This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
Both metal and copper oxidize when exposed to oxygen and this is a natural process. Copper that is exposed to the outside environment is more likely to turn green and that is why copper vases and decorative pieces in gardens are often green.
Best Answer: The best stuff to use is called Phosphoric acid, which is a rust converter for iron. It takes the tarnish/verdigres straight off copper without damaging it. You can also soak copper in cloudy ammonia, but it takes a couple hours, and you have to keep an eye on it, because left too long, it will then turn the copper black. This can be removed though.