Dear Clayarters,
I am having trouble with my porcelain warping severely. I am firing to Oxidation ^9 - low ^10 on a porcelain body from Sheffield clay in a propane fired pre-manufactured computer controlled Olympic Kiln (size: Length 36"x Width 36"x Height 40"x Depth 36"). The firing schedules have been rather fast, about 6-7 hours. I have read conflicting opinions about how long a ^10 firing should be; is this too fast? This Kiln really cooks. I think that may be part of the problem. This kiln is new to us and we are still learning to control it. It has six burners that seem to be too much for this kiln. It only has 4-5 inches of fiber and then a metal casing. The fiber is flat not folded like I have seen in other fiber kilns. As a result I think that this kiln is cooling way too quickly- could this cause the warping? It is mostly happening on bowls but, candlesticks have been leaning too (even when placed in the middle of the kiln away from the burners). We have been throwing the porcelain thinner than our regular stoneware body because we thought we could. We have been bisqueing to ^06 in an electric.
I am not really going for tranlucency, the glazes we are using are mostly opaque or semi tranlucent. Any help would be appreciated.
Thanks,
Cindy at Chilmark Pottery on Martha's Vineyard
Where the beaches are a bit deserted this time of year but, still gorgeous!
