GB/T 30789.7-2015 "Paints and varnishes - Evaluation of degradation of coatings - Designation of quantity and size of defects, and of intensity of uniform changes in appearance - Part 7: Assessment of degree of chalking by velvet method" is applicable to the assessment of the degree of chalking on both rough and smooth surfaces of paint coatings and multi-coat systems, particularly suitable for coatings on mineral substrates. The core method involves using a specified cloth (black wool felt or velvet for light-colored coatings, white velvet for dark-colored coatings) to rotate 180° on the tested coating under consistent pressure to collect powder. The degree of chalking is then assessed by comparing with standard descriptions under diffuse light. Mechanical devices may also be used as an alternative to manual wiping. The test should be conducted on multiple areas of the coating, with the average value and range recorded to ensure objective and accurate assessment results.