Soap Films and Bubbles

Some general references for surface and interfacial phenomenon are the books by Adamson and Gast [2] and Hiemenz and Rajagopalan [3]. An interesting scientific background to molecular and macroscopic properties of soap films and bubbles is provided in [4]. The fluid dynamics, heat transfer, and mass transfer of single bubbles, drops, and particles are covered in [5],... 

The proofs of the more difficult mathematical results have been included in the appendices at the end of the book. These proofs are discussed qualitatively in the main text so that readers, who do not have the appropriate mathematical background, will have no difficulty in following the discussions and explanations. At the end of the book there are references to books, scientific papers, educational films and other information about soap films and bubbles. These references are numbered and some of them referred to by superscripts in the text. 

The lifetime of pure soap films and bubbles is sensitive to the presence of impurities, dust particles, excess caustic alkali or excess fat. Consequently special care is necessary in the preparation of pure soap solutions and the subsequent formation of films and bubbles. This is, however, not true of the synthetic detergents. Only distilled water should be used for soap films with the longest life. 

Since the work of Joseph Plateau many workers have produced recipes for long lasting soap films and bubbles. A summary of these recipes is to be found in the book by J. J. Bikerman and in the original works of Plateau, Boys,i Dewar, Lawrence, etc. It is often useful for demonstration purposes to produce a soap solution that will form films and bubbles with long lifetimes in the open air, without special precautions. The recipes mentioned above have been widely used for this purpose. More recently Cook and Kuehner have described solutions that are particularly good for this purpose. Kuehner has obtained 20 cm diameter bubbles that last for 102 minutes in the open air. 

The educational value of soap films and bubbles should not be overlooked in these concluding remarks. The shapes, motions, and colours of films and bubbles provide a simple means of demonstrating many interesting phenomena to students at all academic levels, from primary school to university. It is my hope that this volume will encourage greater use of soap film and bubble demonstrations and experiments in our schools, educational institutions, and universities. 

Cook, G. A. (1938) Tough Soap Films and Bubbles, Journal of Chemical Education, 15, 161-166. 

C. Isenberg, The Science of Soap Films and Soap Bubbles, Dover PubUcations, New York, 1992. 

In this situation, the equilibrium thickness at any given height h is determined by the balance between the hydrostatic pressure in the liquid (hpg) and the repulsive pressure in the film, that is n = hpg. Cyril Isenberg gives many beautiful pictures of soap films of different geometries in his book The Science of Soap Films and Soap Bubbles (1992). Sir Isaac Newton published his observations of the colours of soap bubbles in Opticks (1730). This experimental set-up has been used to measure the interaction force between surfactant surfaces, as a function of separation distance or film thickness. These forces are important in stabilizing surfactant lamellar phases and in cell-cell interactions, as well as in colloidal interactions generally. 

The stucK of the shapes of soilp dims and bubbles is a fascinating subject. For an account of many simple experiments the reader is referred to the classical book (1890) by C. V. Boys, Soap Bubbles and the Forces which Mould Them, reprinted in the Science Study Series by Heinermum, London, 1960, and by Dover, New York, 1959, or to the more recent book by C. Isenbcrg. Science of Soap Films and Soap Bubbles , Tieto Ltd.. Clcvcdon. 1978. 

For decades, colloid and surface scientists have known that amphiphilic molecules such as phospholipids can self-assemble or self-organize themselves into supramolecular structures of bilayer lipid membranes (planar BLMs and spherical liposomes), emulsions, and micelles [2-4]. As a matter of fact, our current understanding of the structure and function of biomembranes can be traced to the studies of these experimental systems such as soap films and Langmuir monolayers, which have evolved as a direct consequence of applications of classical principles of colloid and interfacial chemistry. As already mentioned in Section I, the seminal work on the self-assembly of planar lipid bilayers and bilayer or black lipid membranes was carried out in 1959-1963. The idea started while one of the authors was reading a paperback edition of Soap Bubbles by C. 

Garti, N. and Bisperink, C. (1998) Curr. Opin. Colloid Interface Sci., 3, 657 —667. Taelman, M.C. and Loll, P. (1994) Multiple emulsions in cosmetics, in Proceedings of Cosmetics Conference, Everberg, Belgium, pp. 213-233. Isenberg, C. (1978) The Science of Soap Films and Soap Bubbles, Tieto, Clevedon. 

Isenberg C (1992) The science of soap films and soap bubbles. Dover, New York... 

The idea is the same as discussed for the bowed dislocation, but we have added a dimension. If we reduce the area of the surface, we lower the energy. Hence, if a surface is curved, we can imagine that there is a force that wants to reduce the area of the surface the force acts on an area of the surface and force divided by area is pressure. Picture how you can take a small ring, fill it with a soap film, and blow a bubble. The pressure is provided by the air if you stop blowing, the surface becomes flat again. 

The scientific study of liquid surfaces, which has led to our present knowledge of soap films and soap bubbles, is thought to date from the time of Leonardo da Vinci - a man of science and art. Since the fifteenth century researchers have carried out investigations in two distinct camps. In one camp there are the physical, chemical and biological scientists who have studied the macroscopic and molecular properties of surfaces with mutual benefit. The other camp contains mathematicians who have been concerned with problems that require the minimization of the surface area contained by a fixed boundary and related problems. A simple example of such a problem is the minimum area surface contained by a circle of wire. The solution to this problem is well known to be the disc contained by the wire. 

THE SCIENCE OF SOAP FILMS AND SOAP BUBBLES as the Laplace-Young equation and states that... 

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