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Chemistry of copper and green skin

I'm doing a research paper on why copper bracelets leave green stains on skin. I would greatly appreciate it if someone could describe the oxidation process and also if they could tell me what exactly a copper salt is and why it is important in turning skin green.

Thank you,

Karly M.
student - Peoria, Illinois, United States of America
2004

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Hello,

I am writing a science essay on copper. I have most of my information except I do not know how or why copper oxidizes. It has something to do with the way it mixes with water and oxygen. I think can someone please help me!

Lori W.
school science project need help - Pickering, Ontario, Canada
2004

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Copper does not really react with water very much. It does not react directly with your sweat when you have copper jewelry on. Rather, it allows sulfur compounds in the air to dissolve into a solution, which is then able to react on the surface of the copper. The main contributor to the green/blue colour is copper (II) sulphate. This copper salt is more soluble than copper (it is blue in solution) and so can dissolve in your sweat, but as the purpose of sweat is to evaporate, tiny crystals are left behind on your skin. This is why the green colour is seen.
The copper is not therefore reacting with water or oxygen directly. I don't know the exact chain of reactions, but I should imagine at some point sulfur trioxide is formed, and dissolves in the sweat to form very dilute sulfuric acid, which can then react with the copper. The process would normally be very slow, which is why you don't see the green/blue colour on the surface of the jewelry (although you do see it on some older things such as the statue of liberty).

Oliver Lonsdale
- Nottingham, UK
2005