Zinssers b i n is the ultimate shellac based primer sealer and stain killer it is perfect for use on interior surfaces and spot priming of exterior surfaces b i n offers unparalleled adhesion to glossy surfaces including glass without the need for scuff sanding and blocks stubborn and persistent stains the high adhesion shellac formula seals porous surfaces with excellent enamel holdout even sealing bleeding knots and sap streaks b i n works brilliantly on water stains mildew stains nicot