This part of ISO 9117 specifies a test for determining the times taken to reach various stages of drying of organic coatings, using a mechanical straight-line or circular drying-time recorder. The use of a mechanical recorder is valuable in comparing the drying behaviour of coatings of the same generic type, when one coating might form a gel at a faster rate than another or might resist scratching better than another. The test is intended to simulate the conditions which exist when painted articles are stacked upon each other.