This Part of ISO 9117 specifies a test method for determining, several stages and the rate of dry-film formation of organic coatings using straight line and circular mechanical drying-time recording devices. The use of mechanical recorders is valuable in comparing the drying behaviour of coatings of the same generic type, allowing that one coating may form a gel or resist tearing at a faster rate than another. The method is intended to simulate the conditions when painted articles are stacked upon each other.