Affordable methods for surface tension and contact angle measurements

In this paper, we present two different experiments aimed at supporting the understanding of surface phenomena at undergraduate level. In the first experiment, we measure the surface tension of several common liquids like water, oil, alcohol, etc by using a simplified custom-built Du Nouy ring apparatus. In the second experiment, the contact angle at the water-glass-air interface is estimated by means of two glass slides that form a sort of variable-size capillary. Materials and experimental apparatuses require a low budget, but the results agree very well with those reported in the literature, obtained with much more sophisticated and expensive equipment. This makes the experiments presented here suitable for educational paths aimed at understanding surface phenomena at undergraduate and even at high school level.