Enamelling is the technique of fusing a glasslike compound on to a metal base.
There is little difference between glass, enamel and ceramic glaze apart from the fact that enamel withstands the metal stresses (expansion and contraction) occuring during and after the firing in the kiln.
The kiln should be pre-heated to 800 degrees C. Most enamels fire at around 780 degrees C but as the kiln loses heat when the door is opened to place and retrieve the work , the firing temperature is about right.
The shorter the firing time the better as this gives more brilliance to the colour than a long soak.
Opaque mature at a slightly lower temperature than transparents and these should fired for a shorter time.
It is always better to under-fire in the first firing, to stabilise the colour which would tend to burn out with progressive firings if the first one is over- fired.
The prepared piece should be placed in the centre of the kiln to ensure an even firing. The temperature in the kiln tends to vary quite a lot from front to back.
As a guide to the firing time, one can count to 20 seconds and then take the piece out. If the enamel is lumpy and does not have a high gloss finish , it has not been fired long enough.
Traditional techniques of enamelling are:
Cloisonne where the enamels are separated by wires.
Champleve where the metal has been etched and these lower levels of metals are then filled with enamels.
Basse-taille where the metal is raised and depressed using the technique of chasing, repousse, carving, engraving and the whole area is then enamelled with transparent enamel.
Scrafitto where the second layer of applied enamel is allowed to dry and is then scratched to reveal some of the base coat.
Plique a jour where the enamel is suspended within a frame work created by piercing out openings in the metal or using wires to build up a design.
Grisaille where a layer of black enamel is applied and subsequently layers of thin white opaque enamels are built up
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