The direct study of oily soil removal from solid substrates in detergency

A novel experimental technique for investigating the removal of small oil droplets from solid substrates by hydrodynamic forces is described. The droplet, in an aqueous environment, is subject to a controlled hydrodynamic flow of axially symmetric geometry, and the technique allows the removal process to be studied as a function of such factors as the contact angle, the interfacial tension, the droplet size and the substrate type, in both the absence and presence of surfactants. Control can thus be exerted over a number of physicochemical factors of primary importance in the detergency process; such control is absent in the traditional Tergotometer approach. An experimental study of both the partial and total removal processes is thus made possible. Some preliminary results are presented.