The finest examples appear to be within the surface rather than on top of it and create a beautiful illusion. The more times transparent colors are fired, the richer they become. The enamelist must become familiar with his medium by testing and timing, in order to reproduce a chosen color scheme as he desires it to be. The firing process is always suspenseful. Overfiring or underfiring can make decided differences in the results.
Some colors are harder or softer than others, and so take differing firing times to mature.
Transparents may be mixed before firing, like blending paint, but opaques do not mix and would produce a salt and pepper effect when fired. Firing transparent color over opaque gives more depth to the overall effect. They are also most beautiful fired directly over the copper. The copper piece should be enameled on both front and back, for a thick coat of enamel on the front without counter enamel on the back would crack eventually. Before it can be enameled, the copper piece is cleaned by annealing, which means it is placed on a rack and put into a 1400-degree or more heated kiln until it turns black.