Abstract: A method and apparatus for producing gypsum board. The method includes the steps of mixing a predetermined amount of fibers, absorbent, and water to form a mixture of wetted, loose fibers, mixing the wetted fibers with predetermined amount of dry calcined gypsum, forming the mixture into a matt having a substantially uniform consistency and compressing the matt to form a board composed of bonded fibers and gypsum. The resulting board has a smooth exterior and can be a homogeneous or a multilayer board.

Abstract: A joint compound for use with an apparatus for taping joints between pieces of wallboard comprises 35-60% by weight of a gypsum base plaster; from about 30-70% by weight of an alcohol-water mixture; 10-25% by weight of polyvinyl acetate; and optionally from about 0-5% by weight of polyvinyl alcohol. The alcohol-water mixture comprises from about 0-30% by weight of water.

Abstract: Decorative interior molding is molded from a slurry of gypsum, water, perlite, and a foaming agent. The slurry is surrounded by paper, cured, and dried.

Abstract: In the production of plaster articles, for example, dental dies and moulds, powdered gypsum (calcium sulphate) is mixed with an aqueous solution of boric acid and/or silicic acid.By incorporating boric acid and/or silicic acid in the mix, the hardness and setting characteristics of the mix are improved. In a typical application the concentration of boric acid in the aqueous solution is from 0.3 to 1.1 grams boric oxide per liter of solution and the preferred concentration of silicic acid in the aqueous solution is within the range of from 75 mls to 300 mls concentrated silicic acid per liter of aqueous solution.

Abstract: A building element based on plaster which is manufactured by dry mixing sand and plaster, by dampening the mixture, by placing the damp mixture in a mold, and by compressing the mixture in the mold while the plaster hydrates in order to densify the crystal lattice of the plaster. The building element (10) includes self-alignment projections (14) on its top face (12) and a vertical groove (22) at one of its ends for the purpose of casting a liquid sealant, such as plaster.

Abstract: In the process for making gypsum fiberboard the boards are formed or molded rom a mash containing calcium sulfate dihydrate and fiberous material. By heating and subsequently cooling the boards the dihydrate is first converted into the hemihydrate and subsequently recrystallized again to the dihydrate. Known processes require day line setting times which are economically disadvantageous. According to the present invention these times are shortened by pulling or drawing water, an aqueous solution or a water containing mixture through the boards after the cooling step. Advantageously a setting accelerating agent can be dissolved in the water. By these features the setting time can be shortened to less than two hours. By addition of a binding agent, e.g. starch, to the fluid drawn through the boards the strength of the boards is increased.

Abstract: A continuous process for the production of gypsum board of variable yet predictable density, wherein a fibrous from of stucco produced from gypsum crystals or fibers is combined with standard calcined gypsum and formed into the board. The density of the resultant board varies inversely with the content of fibrous stucco. The process yields lightweight boards suitable as standard wallboards and inorganic insulating boards.