ISO 19403-3:2017 specifies a test method to measure the surface tension of liquids with an optical method using the pendant drop. The method can be applied for the characterization of liquid coating materials. The applicability can be restricted for liquids with non-Newtonian rheology[1].
NOTE For other methods to determine the surface tension, see e.g. EN 14370 and ISO 1409.

[1] This term is defined in DIN 1342-1.