Colemanite and what its decrepitation does in glazes

Saturday 10th September 2016

Decrepitation refers to a decomposition accompanied by scaling, delayering, even disintegration of the glaze layer. Moving rightward these glazes have increasing percentages of colemanite. At its worst (far right) the glaze is spattering off the sample and onto the kiln shelf. The others are crawling, first pulling away from the corners (far left) moving toward pulling away on the flat surfaces (center). Gerstley Borate and Ulexite, similar minerals, are far less likely to do this (but they have other serious issues also). A much better solution is to use frits to source the oxide B2O3 (easy to do in your account at Photos courtesy of Nigel Hicken.

Pages that reference this post in the Digitalfire Reference Database:

Colemanite, Digitalfire Insight-Live, Subsituting Gerstley Borate in Floating Blue, Use Insight-live to substitute materials in a recipe, Help for Long-time Gerstley Borate Sufferers!

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