Substituting alumina in a clay body dramatically lowered thermal expansion

Wednesday 6th August 2014

These are glazed test bars of two insight-live.com/glossary/43">fritted white clay bodies fired at cone 03. The difference: The one on the right contains 13% 200 mesh quartz, the one on the left substitutes that for 13% 200 mesh calcined alumina. Quartz has the highest thermal expansion of any traditional ceramic material. As a result the alumina body does not "squeeze" the glaze (put it under some compression). The result is crazing. There is one other big difference: The silica body has 3% porosity at cone 03, the alumina one has 10%!

Pages that reference this post in the Digitalfire Reference Library:

Calcined Alumina, Co-efficient of Thermal Expansion, Quartz, Glaze Crazing

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