Experimental Methods for Study of Foam and Antifoam Action

Here we briefly review some of the more important experimental techniques that have been used in the study of antifoam action. Many of the techniques are common to the study of both antifoam action and foam in the absence of antifoam. That is hardly surprising because establishing antifoam effectiveness requires knowledge of the latter. 

Various methods of foam generation that have been used in this context are first described, together with an indication of their respective advantages, disadvantages, and limitations. Although rarely considered in studies of antifoam action, we briefly include the issue of measurement of bubble size distributions because few methods of foam generation conveniently produce monodisperse foam. 

We also describe examples of the various approaches used for the study of the rate of drainage and stability of single foam films. Most of the techniques described have also been used for the study of the behavior of antifoam entities in such films. 

As we describe in detail elsewhere in this book, effective antifoams are usually both oil-based and insoluble in the medium to be defoamed. In order to function, it is necessary that the oil exhibit the property of emerging into the air-liquid surface of that medium. In turn this requires that the film of foaming liquid separating the oil from the air be unstable. The stability of these so-called pseudoemulsion films [1] is therefore a key issue in determining antifoam effectiveness. We therefore review the methods for studying such films. 

Once antifoam oils emerge into the air-liquid surface of the foaming medium, they must exhibit certain types of spreading behavior if they are to be effective in causing foam film rupture. Finally, then, we review the types of spreading behavior to be expected together with brief descriptions of appropriate experimental methods for distinguishing between them. 

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Experimental Methods for Study of Foam and Antifoam Action... 

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