Du Noüy ring method

The Du Noüy ring method measures the surface tension of a liquid by using a thin metal ring. The ring is submerged just below the liquid’s surface, then slowly lifted until the liquid film breaks and the ring separates from the surface. The force needed to lift the ring is related to the liquid’s surface tension. This method provides a precise way to quantify how strongly the liquid’s surface molecules attract each other, which is important in various scientific and industrial applications such as coating, cleaning, and material formulations.