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These SHAB test bars show this body fired from cone 8 (top) down to cone 4 (bottom). The test data indicates it reaches maximum firing shrinkage (FSHR column) at cone 7. Its porosity is 2.5% at cone 6 (ABS column), that is where red color is richest. By cone 5 it has reached 3.8%, that is pretty high for strong functional ware. At cone 7 the porosity is lower, 1.4%, but the color change indicates some decomposition is beginning (signifying possible issues with glaze bubbling, pinholes and warping of ware). Clearly, cone 6 is the most realistic temperature, it is still red and dense enough to have good strength and certainly won't leak if glazes are not crazed.
Glossary |
Cone 5
Also called "middle temperature" by potters, cone 5 (~2160F/1180C) refers to the low end of the temperature range at which most hobby and pottery stonewares and porcelains are fired. |
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