Soap films contact angles

J.A. De Feijter and A. Vrij Contact Angles in Thin Films, n. Contact Angle Measurements in Newton Black Soap Films. J. Colloid Interface Sci. 64, 269... 

Why does a drop of pentane spread into a thin film when placed on a water surface, whereas a larger hydrocarbon such as dodecane breaks up into smaller droplets This is not an academic question, as should be evident from the importance of wetting and contact angle phenomena that we discussed in Chapter 6. Why is it that we can produce relatively stable bubbles with a soap solution but not with pure water Water droplets on an oily surface, dewdrops on a blade of grass, and soap bubbles or foams are so common in our daily life that they rarely engage our attention, but to a scientist they are a constant reminder of the ubiquitous van der Waals forces ... 

Fig. 1.3. Vertical soap film in contact with soap solution A, film without contact angle B, film with contact angle 9.

Yet another mode of foam stabilisation is by finely divided, hydrophobic solid particles such as coal-dust or particles of metal soaps. Their effectiveness arises from their aggregation at. the film surfaces a closely packed layer of solid particles prevents coalescence. However, the phenomenon is very dependent on the surface properties of the solid, since it is necessary for the contact angles to be such that the particles are held in the film. The details of the mechanism have not been fully established, but Figure 12.15(a) suggests a possible configuration leading to stabilisation. 

Princen, H.M. and Frankel, S., Contact angles in soap films from diffraction of light traversing a plateau border, J. Colloid Interface Sci., 35, 386, 1971. 

The application area of surface and colloid science has increased dramatically during the past decades. For example, the major industrial areas have been soaps and detergents, emulsion technology, colloidal dispersions (suspensions, nanoparticles), wetting and contact angle, paper, cement, oil recovery (enhanced oil recovery [FOR] and shale oil/gas reservoir technology), pollution control, fogs, foams (thin liquid films), food industry, biomembranes, membranes, and pharmaceutical industry. 

J. A. De Feijter and A. Vrij, 1. Transition regions, line tensions and contact angles in soap films,/ Electroanal. Chem., 37,9-22 [1972). 

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