ISO 19403-4:2017 specifies a test method to determine the polar and dispersive fraction of the surface tension of liquids with optical methods. The method can be applied for the characterization of liquid coating materials, especially when drying effects occur during measurement. The applicability can be restricted for liquids with non-Newtonian rheology.
ISO 19403-4:2017 assumes that the information of surface tension of the liquid to be tested, as well as at least one suitable reference liquid, is known.
 This term is defined in DIN 1342-1.