This International Standard specifies a method for the determination of the thickness of ceramic coatings by a crater-grinding method, which includes the grinding of a spherical cavity and subsequent microscopic examination of the crater. Because of the uncertainty introduced into the measurement of crater dimensions, the test is not suitable for use where the surface roughness of the coating and/or substrate exceeds 20 % of the coating thickness. NOTE An alternative method for measurement of thickness, using a contact probe profilometer, is given in ISO 18452.