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Abstract

The present invention is directed to the treatment of gypsum plaster prepared from gypsum rock having a substantial content of soluble salts wherein the gypsum plaster is rendered more suitable for manufacturing processes such as the production of gypsum board by rapid and intimate mixing with a flow of cold water followed by rapid separation of the bulk of the water on a continuous filtration apparatus. A preferred form of an apparatus is a suction belt filter and it is preferred that the residence time of the wet plaster on the filter does not exceed 15 seconds. The total time elapsing between initial contact with water and recovery from the continuous filter preferably does not exceed 30 seconds. The salt content of the plaster is considerably reduced by this treatment without significant hydration occurring and the treatment is economic because cold water (up to 40.degree. C.) and no retarder or other additives are preferably employed.

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First Claim