Metalwork: Enamelling on copper

I decided to try using my hot shop colour powders on copper, as I know that copper and glasma have very similar coefficients of expansion, and so can be used together. The problem I was most worried about was it not sticking to the copper. to combat this I thoroughly cleaned the copper so there were no contaminants on the surface. I was right to worry, as my first attempt was unsuccessful, the enamel flaking off the surface soon after it cooled. I thought this was due to the copper building up a layer of oxide, and the powder stuck to that instead of the copper itself. I then thought that to combat this I could use borax flux to stop the oxide building up (flux is what keeps the metal clean and enables solder to stick to it). I first mixed the powder with water and flux and painted it on to the copper.

 I heated up the piece from underneath (to heat the copper rather than the enamel) and the flux bubbled up. I liked the effect this gave, as it moved the powder out of a flat layer and into a very interesting texture.

 I then tried putting the flux on and heating that until it bubbled up, then added the colour powder, this gave a more even layer, though it still kept an interesting texture I think these effects could both be used in future pieces.

I then used enamels that are designed for use in a kiln on sheet glass, which have a lower melting temperature. I textured the copper in the rolling mill then painted on the enamel and heated it with a blowtorch from underneath.

 These stuck without flux, and stayed where I painted them on, so were a lot more controllable, but not as textured as the powder pieces.