: Won't the copper change color or oxidize quickly even under glass?

Dan: I was thinking of using a copper sealant (Everbrite or Permalac) to prevent oxidation. Those applications work for copper fountains and copper sinks (i.e. environments where the sealed metal is regularly or perpetually wet). If I seal and then 'glass over the sealant, I imagine the copper won't oxidize. But I've never tried anything quite like this, so I'd need to try a bit of experimentation.