Zinsser Cover Stain Oil-Based PrimerABOUT COVER STAIN OIL BASE PRIMER Get ultimate hiding power indoors and out with Rust Oleum Zinsser Cover Stain Oil Base Primer. This whole house primer sealer is a favorite with professionals. Use it to block stains, hide dark colors, prevent tannin bleed and penetrate and seal exterior wood. Interior and exterior Best exterior wood sealer Blocks cedar & redwood bleed Seals water, smoke & nicotine stains Sticks to all surfaces without sanding Dries