Thrown pieces made from pure Grolleg and EP Kaolin

Sunday 24th June 2018

These have just been insight-live.com/glossary/359">thrown on the wheel, which we find to be a foolproof method of comparing the plasticity of two clays. They were slurried up and dewatered to about the same moisture content and the same amount was thrown on a potter's wheel to compare the plasticity. While the Grolleg is stickier and dewaters a little slower, it is not nearly as plastic as EPK (which itself is not that plastic either). Curiously, New Zealand Halloysite is quite a bit less plastic than the Grolleg but it responds to plasticity augmentation (in porcelain recipes) just as well as Grolleg (similar amounts of bentonite producing similar plasticities). And, bodies containing EPK need about the same amount of bentonite to produce plasticity suitable for throwing large forms. So, the plasticity a porcelain appears to have by itself is not completely indicative of what it will contribute to a body. The EPK used here is the darker and more plastic of the two varieties we receive.

Pages that reference this post in the Digitalfire Reference Library:

EP Kaolin, EPK fired bar (top) vs Grolleg kaolin at cone 10R. Why shrinking more?, Potter's Wheel

This post is one of thousands found in the Digitalfire Reference Database. Most are part of a timeline maintained by Tony Hansen. You can search that timeline on the home page of digitalfire.com.