Abstract: A continuous manufacturing line for preparing gypsum fiberboard is provided. The manufacturing line includes equipment for admixing hydratable gypsum, paper, and a quantity of water to form a substantially homogenous slurry, dewatering apparatus for removing a portion of the excess water from the slurry to produce a substantially continuous wet web, pressing equipment for configuring the wet web with a compression means to form a substantially continuous green board, a cutting station for cutting the substantially continuous green board into individual uncured lengths, and a heating station for curing the individual uncured lengths to form gypsum-dihydrate-containing fiberboards.

Abstract: An improved composition and process for preparing plaster molds used in casting nonferrous metals is provided wherein plaster molds are prepared from particulate calcium sulfate molding plaster admixed with insoluble calcium sulfate anhydrite whisker fibers.

Abstract: A fire door comprising a core and edge banding, the principal ingredients of the core being expanded perlite, gypsum and cement, and including, as minor ingredients, an organic binder, and having a density not greater than about 35 lbs./cu. ft. The banding comprises composite stiles and rails, each formed of a strip of wood and a strip of a cast mixture of which the principal ingredient is gypsum and including a binder and preferably also including fibers, unexpanded vermiculite and clay.

Abstract: A fire door core in which the major ingredient is expanded perlite and including, as minor ingredients, set gypsum, set hydraulic cement and an organic binder, and having a density of no greater than about 30 lbs. per cubic foot, and preferably including unexpanded vermiculite, clay, and fibrous reinforcements, and a process for making said fire door core, and also a fire door including said core.

Abstract: The water resistance of gypsum products, such as gypsum wallboard, is improved by incorporating in the composition from which the gypsum product is made polyvinyl alcohol and wax-asphalt emulsion.