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The fired bars on the left are Plainsman L215 (with the material we are evaluating). These are a subset of the test bars, cone 4, 2, 02, 04, 06 (top to bottom), ~2150F down to ~1850F. The overlay graph shows pairs of firing shrinkage/porosity lines generated from the data we have been measuring, the descending ones plot increasing density with temperature and the ascending ones plot increasing shrinkage. The further the line-pair intersections push left the lower the temperature needed to mature the clay. But the steeper the lines, the more volatile the material. This data shows L4496 is much less mature till 2050F but suddenly vitrifies and then melts beyond that. The appearance of the bars verifies this. The orange lines would be even steeper were it not for the high sand content. The sand is certainly responsible for the unusually low fired shrinkage up to 2050F.
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Evaluating a clay's suitability for use in pottery
Would you like to be able to use your own found-clays in your production? Follow me as we evaluate a mystery clay sample provided by a potter who wants to do this. |
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