Products / Western Colloid #950 Primer / Sealer - Stain Blocker

A water-based, clear acrylic primer and coating that the technical bulletin says is formulated to stop asphalt residues and oils from staining an acrylic roof coating system and to aid the coating's adhesion to the substrate. It is used as a primer coat over existing granulated asphalt roofing, mastics and coatings, and over solvent-based asphalt mastics and coatings on Western Colloid metal sealing systems; the bulletin says it is not for use over smooth asphalt emulsion or other smooth asphalt or modified bitumen surfaces. It is applied by roller, brush or spray at 1/2 to 1-1/2 gallons per 100 sq. ft., at a minimum of 50 F, and is sold in 5-gallon pails.