The universally accepted technique for measuring interfacial tension is by the Du Noüy ring which is a precise geometry made of Pt-Ir. International standards for both the liquid/gas and liquid/liquid interface, from a range of industries, for example, electrical insulation and electronics, water and environmental, rubber and surfactants are based on this technique. The methods for cleaning the ring are described in these standards but it should be noted that new health and safety rules may preclude their use. Depending on the test material, water or a solvent should be used to remove the test liquid from the surface followed by an acetone rinse and a final clean water rinse before flaming to red heat.

The measurement simply requires the ring to be wetted by the liquid and then pulled through the interface while measuring the force exerted on the ring. The ring must sit square and parallel to the interface as failure do to so will result in errors in the measurements. The maximum force of the vertical constituent is directly proportional to the surface tension. The measuring sensor of the Camtel range of tensiometers is an electronic balance so the weight is monitored and converted to force, for instance, 1cm = 9.81mN. Calibration is done using traceable weights.

When the interface is liquid/liquid, the ring should ideally be zeroed in the light phase. The ring is then cleaned and heavy phase poured into the sample vessel. The ring is positioned under the surface of the heavy phase to completely wet it and while in this position the light phase is carefully pipetted onto the surface of the heavy phase. The interface should be allowed to reach equilibrium before pulling the ring through the light phase.