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These fired bars are nepheline syenite (NS) fired to Orton cone 03 (~2000F). The top bar, L4526C, is 95% NS and 5% Veegum. Its porosity is 3%. The bottom bar, L4526B, is 90% NS and 10% raw bentonite. Its porosity is 19%! The top bar has much higher fired shrinkage, it looks and feels like a porcelain, that is clearly what is densifying it so much (the bottom one looks and feels like Plaster of Paris). Veegum is a super white clay plasticizer, not a flux. But it is acting as the latter here. Or perhaps its surface area enables acting as a catalyst to initiate the melting of the nepheline syenite. Don’t think it’s fair to call the top bar a porcelain? A traditional dental porcelain can be 85% feldspar and 5% clay, this has 5% clay also. This has not matured enough to be a glass ceramic either (modern dental porcelains are pure frit glass ceramic).
Materials |
Veegum
A clay of incredibly small particle size. It has the highest plasticity of any known clay and acts as a suspending and gelling agent in slurries. |
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