This document specifies a method for determining the fineness of grind of paints, inks and related products by use of a suitable gauge, graduated in micrometres. It is applicable to all types of liquid paints and related products, except products containing pigments in flake form (e.g. glass flakes, micaceous iron oxides, zinc flakes). Of the three gauges referred to in 4.1, the 100 μm gauge is suitable for general use, but the 50 μm and especially the 25 μm gauge will only provide reliable results in the hands of skilled laboratory personnel. Particular caution is necessary in interpreting readings of less than 10 μm.