I've got a little idea for a piece that's enamelled and counter-enamelled on 2 pieces of domed copper (back to back) and then surrounded by a strip of pmc in a sort of rough organic way. It will only work if the copper is already enamelled, not enamelled after as the technique is for enamel sifted through a stencil. My question to the experts is, will the shrinking pmc crack the enamel on the domed copper and which is the best pmc (or art clay) to use for this technique? I'm not too worried about over-firing the enamel, as that's part of the look.