QJ 990.15-1986 "Coating inspection method coating drying inspection method" applies to the inspection of our painted products and their surface coatings. This standard describes in detail a variety of inspection methods, including touch finger method, cotton ball method, pressure filter paper method, etc., to determine the degree of drying of coatings. The preparation of the sample should be the same as the actual product to ensure the accuracy of the inspection results. Coatings should be inspected after chilling down to room temperature to ensure that no blocking or plastic deformation occurs. For thick coatings and putty layers, the standard also specifies the application of stripping method and shear drawing method. In addition, this standard also specifically mentions the use of dry grinding and wet grinding methods to inspect the drying degree of the putty layer to ensure that the coating surface is smooth and uniform, and does not stick to sandpaper.