Dynamite® 221 Acrylic Primer & Sizing is a waterbased wallcovering primer and sizing formulated to provide trouble-free wallcovering installations over difficult-to-bond surfaces such as existing vinyl wallcovering, glossy paint, foil, Mylar®, ceramic tile and glass. On porous surfaces such as drywall and plaster, this primer reduces the degree of porosity, allowing the adhesive to bond uniformly to the wall surface. This also provides a greater level of slip when matching patterns and butting seams.