ALSAN RS 222 Primer is a rapid-setting, proprietary formulation polymethyl methacrylate primer. ALSAN RS 222 Primer is utilized to promote adhesion over asphaltic surfaces, masonry, concrete, roof cover boards, wood and other substrates prior to application of ALSAN RS roofing, waterproofing and flashing systems. ALSAN RS 222 Primer reduces the possibility of staining that can occur with ALSAN RS applied directly over asphaltic built-up roofing, asphaltic coatings or asphaltic residue.