Sorry I'm not really sure Sheena I don't use much copper. Here is a sheet on metal finishes, many of them non toxic which might suit you https://dspace.library.colostate.edu...pdf?sequence=1 I also bought a really I. Depth book a while back but it turned out to be mainly for copper so it's still in the wrapper. A lot of chemicals going on to get some great effects though, I particularly liked playing about with rice and vinegar on my fold form plaques!
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