In article . com, professorpaul
says...

Keeping them clean and polished is the problem. You will get a nice
patina -- brown, in the case of copper, which you may or may not like.
Should last forever..


Or that copper-sulphate green-blue if the water is even slightly acidic ... (or
even neutral-testing water, in my observation..)

Banty


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http://news.bbc.co.uk/2/hi/middle_east/5222154.stm