Can a decal firing melt a glaze? Yes!

Friday 9th October 2015

Typical zero-boron high temperature glazes will not soften in a 1500F decal firing. But low temperature glazes will (especially those high in boron). Even middle temperature ones can soften. G3806C, for example, is reactive and fluid, it certainly will. Even G2926B, which has high Al2O3 and SiO2, has enough boron to soften and sometimes create tiny pits. In serious cases they can bubble like the mug on the right. Why? Steam. It was in use and had been absorbing water in the months since it was first glaze fired at cone 03. The one on the left was not used, but it did have some time to absorb water from the air, it is showing tiny pits in the surface. Even if moisture is not present, low fire bodies especially may still have some gases of decomposition to affect the glaze. One more thing: Fire the decals at the recommended temperature, often cone 022.

Pages that reference this post in the Digitalfire Reference Database:

G3806C - Cone 6 Clear Fluid-Melt Clear Base Glaze, Decal, Borate, Glaze Pinholes, Pitting

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