In a similar way to how glaze powder is fused into glass on ceramic, enamel powders are fused onto copper. The temperature however is a lot lower, any higher than 800C and the enamel starts to discolour, as I soon found out.
Before and after shaping the copper needs annealing and then plunging in cold water to cool. Gum arabic is painted onto the back of the shape after cleaning, then backing enamel is dusted on top and the copper placed in a small kiln. When opened the kiln temperature plunges and you have to keep an eye on it as it gradually climbs back up to 799C. On the opposite surface different coloured enamels are fused on in separate firings, although the process is a bit more difficult than I expected. The colours don’t behave as planned, burning out before the kiln reaches optimum temperature or leaving speckled textures (which can look nice – a bit like a dusting of snow).
I’d like to know if these copper enamels can be used on top of bisqued or glazed clay. Alternatively, perhaps panels of enamelled copper (maybe a maker’s mark) could be inlaid into the clay after firing by being stuck on, although I’d have to contest with shrinkage.