Enamel is a very demanding medium. It is glass that is coloured with metal oxides. This colourful material is then fused onto metal using very high heats. There are so many variables that even after years of practice it is difficult to be in complete control of the outcome

There are stress factors between the hardness of the glass and the softness of the metal. There are stress factors in layering enamels which all have different coefficients of expansion, and can often crack or otherwise refuse to bond. 

Of course, this is also what makes it exciting!

cloisonné 

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