Patent ID: 7704316

Claim:
A method of improving an hydraulic binder based coating formulation for coating a building board having a first and second surface, the method comprising: adding to said hydraulic binder a dewatering agent and water, said dewatering agent comprising fly ash, wherein the fly ash further comprises particles having two components with a first larger size component of particles of a 100 micron maximum size in an amount of about 10 to 60 wt % of the formulation based on total dry ingredients and a second smaller size component of particles of about a 10 micron maximum size in an amount of about 5 to 30 wt. % of the formulation based on the total dry ingredients, such that after application of a thin slurry of said formulation to said first surface of said building board, said slurry is dewatered through the building board to said second surface of said building board, wherein the thin slurry is 0.1 to 10 mm thick.