NotesOrganics are literally burned out during first fire of ceramic bodies. Ball clays often contain significant organic material (the lignite imparts their dark grey to even black coloration). Excessive organics and insufficient time or oxidation will lead to black-coring of the body during firing. During this range it is the low temperature organics that are removed, others remain.
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Black coring usually occurs during a reduction firing and is a result of fast firing and/or lack of oxygen in the kiln between 700 and 900C (usually in the bisque firing). If body carbon fails to oxidize to CO2 it steals oxygen from Fe2O3 (reducing it to FeO, a powerful flux.) This FeO will then flu...
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By Tony Hansen
•The secret to cool bodies and glazes is a lot of testing.
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