Abstract: The process makes calcium sulfate alpha-hemihydrate from finely divided calcium sulfate dihydrate by transforming the calcium sulfate dihydrate in the presence of saturated steam. A molded body is formed from the calcium sulfate dihydrate which has a plurality of pores having a pore volume amounting to 15 to 60% by volume of the total volume of the entire molded body. More than 5% by volume of the pore volume contains air. The molded body is fed to the autoclave. In the presence of a sufficient water quantity in the pores the crystal habit and the crystal growth of the calcium sulfate alpha-hemihydrate crystals which grow in an aqueous solution phase are controlled by a process temperature in the range between 110.degree. to 180.degree. C. by the pressure of the process atmosphere in the autoclave. The molded body is removed from the autoclave after recrystallization transformation and delivered for use. Key products of this process and their derivatives are also described.

Abstract: The sodium and/or ammonium salts of a mixture of n-alkyl oxyethylated sulfuric acids in aqueous solution, wherein all the compounds have the same molecular formula CH.sub.3 (CH.sub.2).sub.x CH.sub.2 (OCH.sub.2 CH.sub.2).sub.y OSO.sub.3 .sup.- M.sup.+ being either the sodium or ammonium cation, x being an integer from about 6 to 12, and y being an integer from about 1 to 3.5, a major portion of the mixture comprising compounds where x equals 6-8 and a minor portion of the mixture comprising compounds where x equals 10-12; these mixtures being capable of generating foam of relatively large volume and high stability.

Abstract: The sodium and/or ammonium salts of a mixture of n-alkyl oxyethylated sulfuric acids in aqueous solution, wherein all the compounds have the same molecular formula CH.sub.3 (CH.sub.2).sub.x CH.sub.2 (OCH.sub.2 CH.sub.2).sub.y OSO.sub.3.sup.- M.sup.+, M.sup.+ being either the sodium or ammonium cation, x being an integer from about 6 to 12, and y being an integer from about 1 to 3.5, a major portion of the mixture comprising compounds where x equals 6-8 and a minor portion of the mixture comprising compounds where x equals 10-12; these mixtures being capable of generating foam of relatively large volume and high stability.

Abstract: A water-repellent plaster molding is produced by forming a foam of water, surfactant and polyalkyl-hydrogen-siloxane adding this foam to a paste of plaster powder in water, and letting the mixture set.

Abstract: The sodium and/or ammonium salts of a mixture of n-alkyl oxyethylated sulfuric acids in aqueous solution, wherein all the compounds have the same molecular formula CH.sub.3 (CH.sub.2).sub.x (OCH.sub.2 CH.sub.2).sub.y OSO.sub.3.sup.- M.sup.+, M.sup.+ being either the sodium or ammonium cation, x being an integer from about 6 to 12, and y being an integer from about 1 to 3.5, a major portion of the mixture comprising compounds where x equals 6-8 and a minor portion of the mixture comprising compounds where x equals 10-12; these mixtures being capable of generating foam of relatively large volume and high stability.

Abstract: A method of manufacturing acoustic panels comprising the steps of pouring a solidifiable liquid into a container, placing a porous layer of material onto the solidifiable liquid, solidifying the solidifiable liquid into a rigid layer, and removing the rigid layer and the porous layer from the container. The container has at least one form member extending from the bottom of the container upwardly. This form member extends upwardly into the porous layer. The solidifiable liquid is a slurry of cement. The container and the form member are magnetically attractive. The form member has a generally tapered cylindrical shape and rounded edges. The porous layer is a fibrous material.

Abstract: A method for producing a lightweight set cementitious product, and more specifically, gypsum wallboard, having excellent strength and paper-to-core bond, which method comprises producing a foam comprising polyvinyl alcohol and water, introducing the foam thus formed into an aqueous cementitious slurry, depositing the slurry between paper cover sheets, and permitting the cementitious slurry to set. In a further embodiment an emulsion formed of asphalt and wax is added to the cementitious slurry to impart water resistance, the polyvinyl alcohol of the foaming agent cooperating with the asphalt and wax emulsion to improve the water resistant properties of the set gypsum wallboard.

Abstract: A gypsum wallboard, and the method of manufacture, wherein a defoamer is disposed at the gypsum-paper interface during manufacture, causing the foam, present in the core forming gypsum slurry, to break down at the gypsum-paper interface, increasing substantially the density of the gypsum at the interface, relative to the density throughout the center portion of the gypsum core.

Abstract: Blocks or panels 10, more especially of porous or cellular structure, are faced with a fabric or web inorganic fibres, preferably in the form of glass fibre tissue, bonded to the block or panel by a composition 14 of thermosetting condensation polymer and gypsum, preferably in a ratio between 1:1.6 and 1:4.0. The amount of the composition is preferably such as to provide a film of minimal thickness over the surface of the fabric or web, corresponding to a glass: resin plus gypsum proportion of 8 to 25%. Such coatings when applied to foamed plastics, chip-board or glass fibre panels provide boards suitable for ceilings or partitions and having ample strength and flame resistance. The blocks or panels may be made continuously by applying fibrous tissues, impregnated with a fluid mixture of plaster and resin by roller spreaders, to the face of panel elements supported between release sheets, for example of polypropylene. Pressure may be applied and maintained, if desired, until the fluid mixture has set.

Abstract: Disclosed is a method of making lightweight gypsum products wherein expanded substantially monocellular volcanic ash having a loose bulk density of about 0.05 to about 15 pounds per cubic foot is added to calcined gypsum and water to form a slurry. The hydrated gypsum product formed has a bulk density of about 24 to about 45 pounds per cubic foot.

Abstract: Lightweight gypsum wallboard produced by continuously combining a small amount of surface active agent with a liquid stream which stream is made up of substantially all of the liquids to be used in the manufacture of a continuous web of gypsum wallboard, subjecting this mixture to an intense agitation with vaned saw tooth-like rotary blades in a foam generator while adding a controlled quantity of air thereto, forming a uniformly dispersed foam of very small bubbles from the liquid by completely generating all of the surface active agent therein to form this foam, and mixing this foamed liquid with finely ground dry calcined gypsum in a suitable mixing device to form a foamed settable gypsum slurry, disposing the slurry between paper cover sheets, and forming a continuous web of gypsum wallboard.