Should you use a porcelain as an engobe on stoneware?

Saturday 8th July 2017

This is how bad the fit can actually be. In the front is a bi-clay EBCT test strip of a grogged cone 10R sculpture clay sandwiched with a porcelain. After drying this bar was relatively straight. But during firing the porcelain has a much higher fired shrinkage and it pulls the bar toward itself. During cooling, the sculpture clay has a higher thermal expansion and it pushes from its side bending the bar further. This bar is a bomb of internal stresses, just waiting for a mechanical or thermal stress to bust it into a hundred pieces. Admittedly, putting a thin layer of this onto a piece of heavy ware is not going to bend it. But will it flake off when exposed to stresses (like freeze thaw, being put in an oven, having a hot liquid poured into it, being bumped).

Pages that reference this post in the Digitalfire Reference Database:

EBCT Engobe Body Compatibility Test, Engobe

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