Specifies a method to be used for determining the spreading rate necessary to give a contrast ratio of 98 % of coating materials. The method is restricted to paint films having the tri-stimulus value of Y 70; it is not applicable to fluorescent or metallic paint materials. The principle of the method is based on the Kubelka and Munk equations relating the scattering and absorption coefficients of pigmented films to their colour and opacity. For the determination of hiding power, both the reflectance of a film of thickness, t, on a black background and the reflectivity are required.