You cannot fix this crazing with a process or firing change


Friday 10th April 2015

This is severe crazing (at cone 10R). It is happening because of the chemistry of the glaze, not the firing. The first option to check when fixing crazing is: Can the glaze accept an addition of SiO2? This glaze is an excellent candidate for that because the melt is highly fluid, it will surely be able to dissolve extra SiO2. But it could also accept Al2O3 because it is highly glossy (a little extra Al2O3 will not matte it and would also reduce expansion and increase fired hardness and durability). What to do then? I would start with a 10% addition of a mix of two parts silica to one part kaolin (this mix has a 10:1 SiO2:Al2O3 ratio, about the same as most glossy glazes).

Pages that reference this post in the Digitalfire Reference Database:

The unexpected reason for this crazing can be seen in the chemistry, Crazing


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.