Method and apparatus for measuring surface tension and surface activity of a liquid

A method of measuring the surface configuration of a liquid surface, e.g. to measure surface tension. Liquid samples are confined in wells, e.g. of a multi-well microtitle plate, and a light beam is passed through the sample offset from the centre of the well. The intensity of the reflected or transmitted light beam is dependent upon the angle of incidence with the liquid surface, which varies with changes in surface tension of the liquid. Thus measurement of the reflected or transmitted intensity can be used as a measurement of the surface tension The method can also be used to measure viscosity by agitating the sample and measuring the rate of change of curvature of the sample surface during or after agitation. The method is also applicable to measuring surfaces other than liquids, e.g. of a membrane being deformed under pressure where, again the angle of incidence of a light beam on the membrane varies with deformation of the membrane.