US Patent 10435888 Water stain and sag resistant acoustic building panel

Described herein is an stain and sag resistant acoustic ceiling panel comprising a porous body formed from mineral and cellulosic fibers having an upper surface opposite a lower surface and at least one side surface extending between the upper surface and the lower surface; a first layer applied to the upper surface, the first layer comprising a hygroscopic component and a hydrophobic component; and a second layer applied to the lower surface, the second layer comprising a hydrophobic component.