Enamel

"Enamel :  (Fine Arts & Visual Arts ) a coloured glassy substance, translucent or opaque, fused to the surface of articles made of metal, glass, etc., for ornament or protection"
Source: www.freedirectory.com/enamel

The definition of enamel above is very accurate.  We use enamel powders fused onto copper for ornament, e.g. pendants and wall hangings.
The copper is first cleaned with an abrasive sponge to remove any dirt and grease, and as we use recycled copper there is plenty of that!  The copper is then enamelled with one layer of powder on the back of the piece (counter enamelling).  The piece is then cleaned again to remove firescale before the decorative element is applied to the front. The front of the piece can have anything from two to five layers of enamel powder applied, each layer requiring a separate firing in our small muffle kiln.
We use both opaque and translucent colours to achieve the effect we want, and it’s surprising how many pieces just don’t make it out of the studio because we are not happy with them!