[QUOTE=NATA NOVA; 2361391 ]
volly, especially for you :
How far are you from antiques put here if such links. You do not even bother to read to the end of the article to which you have here
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The article says tint steel, iron and so on. What does my copper saucer ? After all, even an inexperienced person it is clear that the copper in the home environment becomes just such a patina. The truth is not for a year or two, but a much longer period.