3MgO×4SiO2×H2O High-temperature alkaline earth flux in glaze that contibute magnesia and silica.  Promotes smooth buttery surfaces, partial opacity. Similar composition to clay, but in low-temperature clay bodies gives low shrinkage and high thermal-shock resistance, as in standard 50/50 talc/ball clay whiteware body. Highly toxic in inhalation and ingestion. Source: Clay: A Studio Handbook

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