Raw iron bearing clays can be volatile in firing
Thursday 21st August 2014
Here is a good reason not to have single-temperature tunnel-vision when evaluating a insight-live.com/glossary/11">clay body or clay material. This high-iron clay looks great at cone 3 or 4 (the second and third from the bottom, the bottom bar is cone 5 and out-of-place here). But by cone 5 (fourth bar up) the soluble salts (invisible at lower temperatures) begin to melt. Shortly after the clay rapidly descends into serious bloating and then melting by cone 7 & 8 (top bars).
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