What happens when the clay body contracts a great deal more than the glaze in the cooling process?

Unit 7 Topic 16
Using Unity Formula

This can cause the glaze fault called "shivering" in which the fired glaze lifts away from the clay body sometimes flaking off the form.

This phenomenon is the reverse of crazing and is indicated by a very low coefficient of thermal expansion for the unity formula of the glaze and when the difference between the coefficient of expansion for the glaze and that of the clay body is great.

Essentially the glaze ends up being "too big" for the clay body underneath.

In these circumstances if the clay body is very thin and the glaze very thick the clay body may crack (dunt) during cooling as it contracts under the glaze.

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