Why did this piece come out of a decal firing crazed?


Wednesday 11th March 2015

This Cone 10 matte mug has been refired to attach decals. The fired matrix of the body is now brittle and dense and contains millions of quartz grains of many sizes. During the insight-live.com/glossary/330">refire up through quartz and cristobalite inversions each of them experiences sudden volume increases. This does not happen in the glaze because its quartz particles were dissolved in the melt and converted to silicates during the previous glaze firing. The suddenness of the expansion depends on the rate of temperature increase and its extent depends on the size of the quartz particles. The body's passage through these two zones stretched the glaze and cracked it. Had the glaze fit been better (under some compression) it would likely have been able to survive.

Pages that reference this post in the Digitalfire Reference Library:

Quartz Inversion, Ceramic Decals, Refiring Ceramics, Glaze Crazing


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