Tannin stain blocking additives were developed to augment resin technology in stopping the migration of these soluble stains to the surface of the paint. Blocking tannins and other common wood stains (sap, rosin, or other oleo resinous substances) can be quite daunting for water-based coatings. Tennants SBA stain blockers come as liquid additives which are formulated into paint where they are designed to react with soluble tannins to form insoluble complexes