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Gypsum (Calcium Sulfate Dihydrate)

Results: Between 100 and 300°C, the double-step dehydration of the calcium sulfate-dihydrate occurred. In the first step, 1.5 out of 2 water molecules were released from the system and half-hydrate was formed. In the second, the half-hydrate dehydrates further on and forms anhydrate. Starting at 348°C, the anhydrate converts to β-calcium sulfate (exothermal effect). At 1219°C the β-calcium sulfate converts to α-calcium sulfate, clearly visible as a sharp exothermal effect in the DSC curve. At temper- atures above 1250°C, a further mass loss can be seen. This mass loss refers to the sulfate decomposition. Calcium sulfate converts into calcium oxide. The enodthermal peak at 1380°C is due to melting of an eutectic mixture of calcium sulfate and calcium oxide. AS-009-2006 STA 409 PC Luxx®

Digital Fire: Pin holed Glaze Pinholes in glaze after firing. Caused by gas evolution from body and/or glaze during firing. (3) Soluble salts (sulphates) in body. (a) Add 0.01 - 0.25% Barium Carbonate to the body.

Materials such as manganese dioxide in clay can give off oxygen in glost and decorating fires if they are not decomposed during bisk firing. REFERENCES

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Page last modified on September 23, 2011, at 11:40 PM