Here's a couple tips I picked up about enameling on metal clay:
- Metal clay is porous after firing, so it needs to be burnished before applying enamel to smooth out the surface. Otherwise the metal clay will kind of suck up the enamel. You can burnish it by hand, but it takes quite a bit of elbow grease. I find that tumbling with steel shot for an hour does the trick.
- You need to be super careful not to get any stray grains of enamel on the un-enameled parts of your piece. Any stray grains will make a nasty brown or black mark on your piece. I find that wet packing the enamel works best to keep it where it needs to be.
- Keep the metal under the enamel nice and thick- I've had good results with rolling the clay 1 mm thick, as long as I keep the layer of enamel nice and thin. If the metal is too thin or the enamel too thick, the enamel will crack off.