Two-material porcelain much better with ball clay than kaolin

Sunday 10th March 2019

Left: 65% #6Tile insight-live.com/material/925">kaolin and 35% nepheline syenite. It's white but crazes the glaze and has 1% fired porosity (measured in the SHAB test). Thus it does not have porcelain density. Plasticity is very good. Right: 65% M23 Old Hickory ball clay and 35% nepheline syenite. The glaze fits, the body has zero porosity (very dense) and plasticity is fantastic! The body on the left needs a 20% silica addition (to stop crazing) and 5% more nepheline (to reduce porosity to porcelain levels). But the remaining 40% kaolin will not be nearly enough for a workable plasticity (so bentonite will be needed). The body on the right does not need fixing because ball clay is easier to flux with feldspar and it contains its own natural silica.

Pages that reference this post in the Digitalfire Reference Library:

Ball Clay, Formulating a body using clays native to your area, Stoneware, Porcelaineous Stoneware

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