Abstract: A method of producing an opaque adherent coating on the surface of a substantially hydrated cementitious substrate is provided. A waterborne storage stable sealer comprising an aqueous medium containing a binder polymer and an opacifying polymer is applied on the surface of such a cementitious substrate. Upon drying the layer substantially hides the primary efflorescence typically present on the surface of the cementitious substrate. Applicants have unexpectedly discovered that by optimally adjusting the thickness of the coating a weight amount of waterborne storage stable sealer solids in the waterborne storage stable sealer and a pigment volume content of the opacifying polymer in the storage stable sealer the opaque adherent coating is produced on the surface of the substantially hydrated cementitious substrate.

Abstract: The present invention is directed to producing an efflorescence resistant sealer coating on a cementitious substrate, such as, a roof tile. A foamed layer of an efflorescence resistant coating composition is preferably applied on the surface of a wet cementitious substrate. The wet cementitious substrate is then hydrated to produce the cementitious substrate having the efflorescence resistant coating thereon. If desired, the efflorescence resistant coating composition is provided with a pigment to produce a pigmented efflorescence resistant coating on the cementitious substrate or a clear efflorescence resistant coating of the present invention may be applied over pigmented cementitious substrate. The efflorescence resistant coating produced in accordance with the process of the present invention substantially reduces the formation of esthetically unpleasant efflorescent layer on cementitious substrate surfaces.