The method is of general use for comparing similar pigments, for example a test pigment against an agreed reference pigment. The pigment is dispersed in stages under specified conditions in an agreed binder system. After each stage, a portion of the mill base is taken and its fineness of grind is determined as described in ISO 1524. The fineness-of-grind values are plotted graphically as a function of the dispersion work done (expressed as time, number of revolutions, etc.). From the graph, the work necessary to obtain an agreed fineness of grind is determined.