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 made into a composition that is applied to a substrate and dried or stoved. The specular gloss of each dried film is determined as described in ISO 2813. The gloss values are plotted graphically as a function of the dispersion stage (expressed for example as time, number of revolutions of a muller). From the graph, the dispersion work necessary to obtain an agreed specular reflection value is determined.