Talc - 1kg
MgO 32/33%, SiO2 46%, CaO up to 8%, Al2O3 up to 9% typical Important source of MgO flux for bodies and glazes. Talc has a less high loss on ignition than dolomite or magnesium carbonate and so produces less glaze bubbles, blisters and pinholes. High temperature magnesia matt glazes often use talc and magnesium carbonate together to form magnesium silicate crystals on cooling to give opacity and a silky surface. Reduces plasticity in bodies and so is more suitable for castware. Used to produce thermal shock resistant / flameproof stoneware bodies where it acts as a low expansion flux converting quartz in clays to magnesium silicates. In amounts up to 5% it can improve maturity and melting. Mix into a paste before adding to glaze batches.