|Monthly Tech-Tip |
This is a thin slip-cast plate made from a high-silica (therefore high thermal expansion) clay and a thick layer of low thermal expansion glaze. During the cooling in the kiln the clay shrinks and the glaze shrinks less. This puts the latter under compression, and the body under tension. A ceramic does not do well under tension. A week after firing the piece spontaneously cracked to relieve the tension.
Dunting generally refers to firing cracks that occur in ceramic ware as it is cooled in the kiln. The reason is generally uneven cross section or too rapid cooling.