Methods of preparing gypsum board using cellulosic fiber

A method of making gypsum board comprising:

• preparing a core slurry comprising water, stucco, foaming agent, and cellulosic fiber and strength-enhancing starch in an amount of 4% or less by weight of the stucco;
• preparing a dense layer slurry comprising water and stucco;
• adding cellulosic fiber to the dense layer slurry in an amount of 2% by weight of the stucco or less;
• applying the dense layer slurry in bonding relation to a first cover sheet;
• applying a first surface of the core slurry in bonding relation to the dense layer;
• and
• applying a second cover sheet in bonding relation to a second surface of the core slurry;
• the board having a density of 32 pcf or less and a nail pull resistance of at least 65 lb according to ASTM 473-10, method B.

A method of making gypsum board comprising:

• preparing a core slurry comprising water, stucco, foaming agent, and cellulosic fiber in an amount of 0.5% to 1.5% by weight of the stucco;
• preparing a dense layer slurry comprising water, stucco, and cellulosic fiber in an amount of 0.7% to 2% by weight of the stucco, the dense layer slurry excluding foaming agent;
• applying the dense layer slurry in bonding relation to a first cover sheet;
• applying a first surface of the core slurry in bonding relation to the dense layer;
• and
• applying a second cover sheet in bonding relation to a second surface of the core slurry;
• wherein:
• the dense layer slurry preferentially contains a greater concentration of the cellulosic fibers than the core slurry,
• the dense layer slurry includes the same or lower amount of starch, dispersant, accelerator, retarder, and polyphosphate, as compared with the core slurry,
• the board having a density of 32 pcf or less and a nail pull resistance of at least 65 lb according to ASTM 473-10, method B.