This Part of EN 13523 describes the procedure for determining objectively the chalking resulting from natural or artificial weathering of an organic coating on a metallic substrate. The advantage of this procedure for measuring chalking of an organic coating is that the result can be read off immediately on an instrument. Subjective judgement by visual comparison of test specimens with reference specimens is not necessary. Reproducible results can only be obtained by careful execution of the test. Special attention is paid to the adhesive tape and its application to the test surface. The test method is not applicable to embossed coatings. In the case of textured coatings, the degree of texture will influence readings. Also dirt collection can influence readings on outdoor weathered specimens. NOTE Different methods for assessing chalking are in use. The results of these different methods are not comparable.