FOAM FORMATION AND FOAM STABILITY By R. MATALON, Ing.Dr., Ph.D.* THE STUDY of foams has attracted' foaming agent produces a very dense a great number of scientists and technicians. Fundamental research was carried out in order to investigate the mechanical properties of the stabilising layer responsible for the lifetime of lamin•e and bubbles along the foam column. As a result of this investigation it is now possible to increase or decrease the foam stability. A large number of industries are interested in this foaming property. Increase in foam volume and foam stability is sought by the soap and' detergent manufacturer and by the cosmetic chemist, in various branches of their industries. Laundry pow- ders, liquid soap, shampoos, shaving creams, etc., are formulated to have a common feature of foam abundance and foam stability. Foam production is also aimed at in many other industries, such as in the manufacture of aerated choco- lates, meringues, etc., and in the production of cellular concrete for building materials. One very useful application of foam production is undoubtedly in fire extinguishing materials. Here the * Chemistry I:)epartment, King's College, University of London. 216 toam of great stability to heat. 'Essential components of fire-ftghting foams are hydrolysed blood protein tanned with various metal ions such as ferric chloride, etc. Foams also constitute an impor- tant item in the beer industry and the brewers are interested in keeping a good head of foam in the .glass. It follows that foams play an important and useful role in several industries. They-are also very attractive, and the production of •nulticoloured bubbles using a pipe, a tube or a ring is an amusing pastime for children. Bubbles have been lately used for publicity purposes as well as on the stage. On the other hand, foaming con- stitutes a nuisance in several indus- tries, for example, in vacuum distilla- tion and in fermentation, causingi:: the vats to overflow. In the photo- graphic paper industry, the tendency of gelatin to produce bubbles on the/': paper results in a non-homogeneous deposit of the silver bromide emul-: i sion and in the appearance of white spots. Hence a great number of:• "antifoams" are now proposed, to overcome foaming when it is unde -'i sirable. :i': ..,

FOAM FORMATION AND FOAM STABILITY Figure I. Torsion head and driving mechanism of the author's automatically recording apparatus for producing traction and retraction curves. 217