This International Standard is one of a series of standards dealing with the sampling and testing of paints, varnishes, printing inks and related products. It 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. 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 than10 µm.