Surface Preparation Substrates must be stable, clean and free of substances likely to impair adhesion. To ensure full and even curing of the foam, moisturize mineral, porous substrates (brickwork, concrete, limestone) with water spray before application. At low temperatures special care has to be taken to avoid freezing of the water on the surfaces. Mask off adjacent areas with foil. The surfaces can be moist, but not frosted nor iced.