I’m playing with glass fusing, and copper oxide on the glass would leave a lovely turquoise color. I’ve got some copper, so what can I do next?
The surface will already be cupric oxide. To speed up the rest of it doing that, turn it into powder. How best to do that I leave as an exercise to the reader.
If the copper is already finely divided, heating it should do. Otherwise, you might better look for a source of copper oxide.
Currently on EBay:
In these DIY solar cell projects, they just have you heat a copper plate on an electric stove until a thick layer of black copper oxide builds up and flakes off. Perhaps grind it up finer with a spoon in a ceramic bowl? (And does this dissolve and stain the glass bluegreen, or does it keep together and just remain black?)
Yeah, heating copper makes it oxidize so quickly it forms big fragile flakes that crumble off. I am not sure of the temperatures but think the range between 500 and 1000 ºC would do well. It melts a bit above 1000 ºC. I think putting it on an electric stove burner would work, but it would make a mess. You could probably buy a replacement element and wire it outdoors, if you know the electrical craft well enough. The ceramic-topped hotplates we have in the lab at work do it just fine.