ISO 12137:2011 specifies a method for determining, using a curved (loop-shaped or ring-shaped) stylus, the mar resistance of a single coating of a paint, varnish or related product, or the upper layer of a multicoat system.
This test has been found to be useful in comparing the mar resistance of different coatings. It is most useful in providing relative ratings for a series of coated panels exhibiting significant differences in mar resistance.
ISO 12137 does not specify a method using a pointed stylus, two of which are specified in ISO 1528‑1 and ISO 1528‑2, respectively. The choice between the three methods will depend on the particular practical problem.