Apparent contact angle and triple-line tension of a soap bubble on a substrate

The contact angle, theta, of a small bubble on a flat solid substrate was m easured as a function of bubble radius, R, The observed deviation of the co ntact angle from 90 degrees can be accounted for in terms of a negative lin e tension, tau. The measured values of \tau\/gamma (f), where gamma (f) is the film tension, ranged between 0.15 and 0.6 mm and are proportional to th e height, h, of the Plateau border, with \tau\ congruent to 1.7 gamma (f)h. (C) 2001 Academic Press.