|Monthly Tech-Tip |
These mugs are quite thin walled. A glaze has just been applied to the inside. Notice how it has water logged the bisque (you can see the contrast at the base, where the clay is a little thicker and has not changed color yet). Although there may be enough absorbency that a glaze could be applied now, it would still not be a good idea because it would completely waterlog the piece and result in a very long drying time. This is bad, not only because of process logistics, but also because slow drying glazes almost always crack and lift from the bisque (causing crawling).
Potters and some manufacturers fire ceramic ware twice, once to prepare it for glazing (call bisquit firing) and the second time to melt the glaze onto it.
A ceramic glaze fault that occurs during firing of the ware, the molten glaze pulls itself into islands leaving bare patches of body between.
Ask yourself the right questions to figure out the real cause of a glaze crawling issue. Deal with the problem, not the symptoms.