These test bars were fired from cone 10R and 11 oxidation down to 7. The porosity first dips under 1% at between cone 11 and 12 (rather than the normal cone 4)! By cone 8 it rises to 10%. Fired shrinkage is 8.5% at cone 11 dropping to 5% by cone 8. Drying shrinkage is about 3.5%, up to 1.5% less than normal. Normally, PV clay is a naturally occurring mid temperature plastic porcelain. This, by contrast, is a non-plastic, high temperature stoneware (it has 2.5% porosity at cone 10R, so it is far from being a high fire porcelain). Any company that used this shipment in its clay body production faced dramatic changes in their fired and plastic properties if they have been using the more melted version before. The level of maturity presented by these test bars was considered more "normal" by body manufacturers.
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