Abstract: An abuse-resistant, cast acoustical ceiling tile having improved impact resistance and excellent sound absorption values. The ceiling tiles have aggregate particles applied to the surface of a wet pulp in the casting process and the particles are embedded in the pulp by compression with a roll and/or smooth plates. The aggregate particles have an average particle diameter of at least about 1,000 microns. The ceiling tiles have excellent sound absorption properties with a noise reduction coefficient (NRC) of at least about 0.50. Calcium carbonate is the preferred aggregate particle material.

Abstract: A sag resistant, cast acoustical ceiling tile which has a mineral wool core and a starch binder and which has a formaldehyde resin impregnated paper backing. A kraft paper backing which has been impregnated with a melamine formaldehyde resin has been found particularly effective in providing sag resistance in high temperature, high humidity conditions such as encountered in Pacific Rim countries. A method has been developed to manufacture the sag resistant, cast acoustical ceiling tile wherein water is applied to the paper backing prior to machining and painting to provide a tile which has a relatively flat initial plane position.