stephani stephenson on fri 13 apr 07
hi donna, are you asking what happens if you refire the cone 6 clay to cone 05-06 with the cone 05-06 on it?
just checking. that's what i get from your question anyway.i have used some cone 06-05 glazes on very vitreous quarry tile.( Though i do not know what temp the quarry tile was fired to. my guess was it was much higher than cone 05) my glazes melted well on it and i did not see the problem you describe... main difference was using less water in the glaze, either plopping it on like pudding or deflocculating it somewhat to get this effect...because you have to put more glaze on top of the tile, and use a glaze which is durable in the dried raw state....due to the fact nothing is getting absorbed into the tile when the glaze is applied....so all the wter has to evaporate off the glaze surface instead of getting pulled down into the clay body... with some glazes this does affect the way the ingredients get laid down
. the glazes did look different on this clay body, but then they pretty much look different on every clay body. but the fit seemed OK.
i've use glazes on other cone 5 clays fired to cone 5, but those clays were not necessarily vitreous at that temp so, didn't notice much difference..
sounds like you have a specific situation with specific materials
when you say the glaze is shringking do you mean it is shrinking in drying or
are you referring to the difference in coefficient of expansion when fired?
does the glaze have a high clay content?
the dimpling you describe, does it seem like an 'elephant skin' ,something lookinf more like shivering ,vs. crazing?
just trying to picture it.
Has anybody tried putting low temp glazes (cone 05-06) on a cone 6 clay body that has been fired to maturity (with no glaze)? Brushing the glazes on and getting them thick enough is not a problem. The problem is the glaze is shrinking and the body is not, causing a dimpling and thinning which, with red glazes, turns dark.
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