Bubbles in Terra Cotta transparent glazes. What to do?

Tuesday 4th November 2014

Two transparent glazes applied thickly and fired to cone 03 on a terra cotta body. Right: A commercial bottled clear, I had to paint it on in layers, I ended up getting it on pretty thick. Left: G1916S, a mix of Ferro insight-live.com/glossary/43">frits, nepheline syenite and kaolin - one dip for 2 seconds and it was glazed. And it went on more evenly. Bubbles are, of course, generated by and clay body during firing, but terra cottas are the worst. And when fired toward vitrification the gas volume can really increase. Complicating this is the fact that low temperature glazes melt early, while body gassing may still be happening. Improvements? Both of these could have been applied thinner. And I could have fired them using a drop-and-hold and a slow-cool schedule. But the biggest improvement would likely be firing lower, to cone 04.

Pages that reference this post in the Digitalfire Reference Library:

Kaolin, Glaze Bubbles, Transparent Glazes, Glaze thickness

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