SM Primer is a ready-to-use, water-based latex primer for Mapei self-adhesive membranes with removable paper. It is used on indoor and outdoor floors, both in residential and commercial applications. SM Primer contributes to the adhesion of Mapei membranes with release paper to concrete, plywood and other approved and properly prepared substrates. It is applied by brush or roller. It start off white but becomes transparent during drying, allowing the user to see the guidelines on the substrate even after application. Its quick drying, allowing membrane installation after about 15 minutes.