A problem with brilliantly colored fluid-melt glazes: Micro-crystals

Thursday 7th January 2016

insight-live.com/glossary/132">Crystallization (also called devritrification). You can see the tiny crystals on the surface of this copper stained cone 6 glaze (G3806C). The preferred orientation of metallic oxides is crystalline. When kilns cool quickly there is simply not enough time for oxides in an average glaze to organize themselves in the preferred way and therefore crystals do not grow. But if the glaze has a fluid melt and it cools slowly through the temperature at which the crystals like to form, they will. There is another issue here also: There are tiny dimples in the surface. This is because copper carbonate was used here instead of copper oxide. During firing, it generates carbon dioxide (because it is a carbonate) that bubbles out of the melt, leaving behind dimples that may or may not heal during cooling.

Pages that reference this post in the Digitalfire Reference Library:

G3806C - Cone 6 Clear Fluid-Melt transparent glaze, Crystallization, Fluid Melt Glazes, Colorant, Runny Ceramic Glazes

This post is one of thousands found in the Digitalfire Reference Database. Most are part of a timeline maintained by Tony Hansen. You can search that timeline on the home page of digitalfire.com.