Michele Dupas Posted August 14, 2014 Report Share Posted August 14, 2014 I made a teapot and the exterior has bisqued with terra sigillata. I then glazed the interior with my clear glaze and fired to cone 6. The interior clear glaze seeped through in spots leaving dark patches. I believe these areas are where the interior glaze was the thickest. Any idea what caused this and if it is a terra sig/glaze reaction or the terra sig is so poreous that regardless of what glaze I choose it will bleed through? Link to comment Share on other sites More sharing options...
neilestrick Posted August 14, 2014 Report Share Posted August 14, 2014 Photos, please. Link to comment Share on other sites More sharing options...
Tyler Miller Posted August 14, 2014 Report Share Posted August 14, 2014 The glaze recipe, if you have it, might also be of some help. Sometimes a glaze can have soluble/semi-soluble components and these can cause what you're talking about. In my experiments with borax fluxed glazes, I've found this phenomenon especially common--the soluble flux is absorbed into the body through along with the moisture. We could maybe help reformulate with a non-soluble source of flux. Doesn't terra sig lose its sheen at a very low temperature, though? Link to comment Share on other sites More sharing options...
Min Posted August 14, 2014 Report Share Posted August 14, 2014 Doesn't terra sig lose its sheen at a very low temperature, though? Yup, ^02 is about as high as it will go without loosing its shine. According to Vince Pitelka above that the clay shrinkage will cause the shine to diminish and leave a satin surface. Also, if the terra sig is made with earthenware clay then at ^6 it won't bear any resemblance to terra sig. Link to comment Share on other sites More sharing options...
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