Patent ID: 8147629
Filing Date: 2012-04-03
Classification: B28B,E04B,Y10T

Abstract:
1. A method of making a suspended ceiling tile comprising calcining gypsum in a dilute water slurry, under pressure, with at least 90% of the solids being about 8% to about 30% cellulose fibers and the respective compliment being of gypsum, dewatering the slurry before rehydrating the gypsum, and rehydrating and crystallizing the gypsum in and about voids in the cellulose fibers to form a homogenous non-air-permeable, rigid preform composite board and after the preform board has set by rehydration and crystallization of the gypsum, cutting a plurality of holes in a face of the preform board by removing the material in the space of the holes to lower its effective weight and to increase its NRC, the hole cutting and/or subsequent processing leaving the holes blind at the side of the tile opposite said face and in essentially free communication across their individual areas with the atmosphere at said face, said holes being cut through said board, and a side of said board is covered with an imperforate web adhered to said side.