One reason why Gerstley Borate can make glaze difficult to use

Sunday 14th June 2015

This glaze slurry contains 30% Gerstley insight-live.com/glossary/129">Borate. I poured it onto a plaster table and it can take five or ten minutes to dewater enough to form it in test balls. A typical glaze would dewater twenty times faster! Gerstley Borate contains microfine clay (e.g. hectorite, bentonite), the percentage is high enough that it voraciously hangs on to the water it has. This is the reason that many GB glazes take a long time to dry on bisque ware. And why they require more water and gel the slurry. Generally, slow drying also means cracking, that in turn can lead to crawling.

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Gerstley Borate, Glaze Gelling

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