A method for identifying surface imperfections such as pinholes and deep scratches in primer. Requires no masking and there is no dry time involved. Can be used for both wet and dry sanding. Contains no solvents. Kit contains an applicator pad. Used in the 3M Dry Primer Sanding System. When sanding polyester filler, it ensures the filler is flat (no ripples) and that the body styling lines and contours are straight and correct. It also ensures the total primed area is sanded prior to top coating.