Patent ID: 8702881

Claim:
A method for making a fire resistant gypsum panel, the method comprising: (A) preparing a gypsum slurry having high expansion particles of unexpanded vermiculite dispersed therein, wherein the volume expansion of the vermiculite particles average about 300% or more of their original volume after being heated for about one hour at about 1560° F.; (B) disposing the gypsum slurry between a first cover sheet and a second cover sheet to form an assembly comprising a set gypsum core with the high expansion particles generally distributed throughout the gypsum core; (C) cutting the assembly into a panel of predetermined dimensions; and (D) drying the panel; such that the set gypsum core has a density (D) of about 40 pounds per cubic foot or less and a core hardness of at least about 11 pounds, and the gypsum core and amount and distribution of the vermiculite particles within the core are effective to provide a Thermal Insulation Index (TI) of about 20 minutes or greater.