an aqueous dispersed primer - sealer composition applied to a surface layer of overlay paper or surface mat provides an impregnated surface layer for use in manufacturing hardboard products by hot pressing in a molding operation . the primer sealer provides a finished surface as well as defect - free surface from the molding surface . the primer - sealer can be pigmented and is based on a polymeric binder composition containing melamine resin , carboxyl functional acrylic emulsion copolymer , vinyl - acetate - vinyl versatate copolymer , emulsified fatty acid , and polyvinyl alcohol .