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is soda ash safe to use in my kiln or will it contaminate it?

updated tue 15 feb 05


Llewellyn Kouba on mon 14 feb 05

I am getting ready to fire a cone 04 terra cotta load soon. I have been
toying with mixing up a glaze or engobe that has Soda Ash or sodium
bicarbinate (spelling?) in. If I use this in my kiln I feel it will
continue to sinter and move around in subsequent kiln loads and I won't
like this on wares that I want perfectly smooth glaze surfaces. Am I
correct on that. I also wonder about putting into the kiln a single
tile chimney flue I have on hand and use as a sagar and if I close the
top very secure will this contain the salts enough to prevent
contamination in my kiln etc.? How much of an issue is soda ash for
contamination in a kiln that isn't normally used for soda firing. etc.
Salt firing is one thing but is Soda firing eqaually as bad or about the
same restrictions etc. Can someone elaborate on this a bit more
please. If there is some doubt I would not risk it. I also have no clue
how high a temperature the clay tile saggar can withstand? I don't have
a small piece on hand that I can fire in 04 to find out first but maybe
better try and find a piece on the same brick pile. Any helps would be

Llewellyn Kouba
Abbey Pottery