ISO 6889:1986

Surface active agents — Determination of interfacial tension by drawing up liquid films

The determination is carried out in the following way: Measurement of the maximum force which can be exerted before the film breaks, the force being exerted vertically on a stirrup or ring, in contact with he interfacial liquid film between two immiscible liquid phases placed in a measuring cup, in order to draw up the interfacial film. The force must pass through a maximum, otherwise the measurement is not valid.