BAL APD Primer 2.5LBAL Prime APD is a rapid drying acrylic primer suitable for priming wall and floor backgrounds prior to the fixing of ceramics, mosiacs and natural stone tiles in dry or wet interior and exterior environments. BAL Prime APD stabalises dusty surfaces and reduces the porosity of backgrounds and may be used undiluted to prime plaster walls, tongue and groove floorboards. Use diluted on plaster walls (if dusty or porous), Anhydrite and cement floors. Use