Can bone-dry ware be glazed too thickly? Yes! When the specific gravity is 1.7.

Monday 7th August 2017

In testing to determine the best specific gravity (SG) for this insight-live.com/material/260">Darvan-deflocculated glaze slurry (G2926B), I arrived at what I thought would be great: 1.7. For 2.5kg of glaze powder only 1100g (1100ml) of water is needed, half the normal amount. And the slurry flows well. There appears to be enough water to form a good bond with the body. But a one-second dip of a bone dry piece produces twice the desired thickness, it dries too slowly and it is running. So, what should the SG be? I'll keep increasing the water until I can induce some thixotropy to hold it in place (using Epsom Salts), and it goes on thinner in a quick dip. If thixotropy is difficult, I’ll add 1% bentonite to increase particle surface area. And, I'll document the results at each step for future reference (in my Insight-Live account). Of course, these are going to need help drying, either by preheating the ware or putting the pieces in a drier.

Pages that reference this post in the Digitalfire Reference Library:

Drip glazing and bare outsides: Deceptively difficult., Specific gravity, Once-Fire

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