Of the air while replacing it with fresh air. Having little or no air movement, (2) equal temperatures throughout the entire area, and (3) provisions for exhausting a portion The best drying rooms or ovens provide (1) uniform and rapid circulation (minimum of 15-30 fps) of air with no “dead spots” This produces a hard spot, giving uneven absorption.ĭrying All pottery molds should be dried as quickly as is safely possible after manufacture so that maximum physical properties can develop. The point where it strikes the surface of the case. Pouring a large amount of slurry directly on the face of the case mold may result in slight densification of the plaster mold at Whenever possible, the plaster slurry should be poured carefully in the deepest area so the slurry flows evenly across the surface of the case mold. Agitation of the filled case mold is a further step used to prevent air at or near the mold surface. Pouring To prevent air entrainment and provide a uniform, smooth surface, careful pouring of the plaster slurry is necessary. Longer mixing times result in higher mold strength and shorter setting times. Proper blade and bucket dimensions are important for obtaining the best batch mix Plasters can be mechanically mixed throughīoth batch and continuous processes. Mechanically mixed plasters develop uniform molds with optimal strengths. Mixing Mixing the plaster slurry is one of the most important steps in producing plaster molds with maximum strength, absorption, hardness, and other important properties. See bulletin IG503 for specific soaking instructions. Small batches require less soaking than large batches. The plaster should be fully dispersed in the water prior to mixing. Do not drop handfuls of plaster directly into the water. Soaking Sift or strew the plaster into water slowly and evenly. The water-to-plaster ratio is critical because it governs both the strength and the absorptive capacity of the mold. Weigh both the plaster and water for each mix. The higher the temperature of the water, the shorter the set time. Since variations in slurry (the plaster and water mixture) temperature produce variations in setting time, it is important to keep both the plaster and water in a stable temperature environment prior to use. Preparing the Mix Use potable water at temperatures between 70° and 100° F (21° and 38° C). Compressive Strength 1,200 psi 8.2 MN/m2ĭry Compressive Strength 2,700 psi 18.4 MN/m2 Use Consistency (parts of water by weight per 100 parts plaster ) 66 66ġ Hr. – Available with or without thermal shock additive. – Unique, specially-designed plaster for use with mechanical clay-forming machinery. Absolutely the hardest, most wear-resistant plaster made for molds, and a favorite for jiggering molds. PURITAN POTTERY PLASTER is a unique, specially designed for use with mechanical clay forming machinery.
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