ABSTRACT
Foam generation rst leads to the formation of wet foam that consists of spherical air bubbles surrounded by a liquid. While draining, the structure gradually changes as the liquid content of the foam decreases and the air bubbles are transformed into polyhedral air cells separated by thin liquid lms that are stabilized e.g. by surfactants adsorbed at the water/air interface. Although the application of liquid foams is widespread (cleaning agents, beverages, re- ghting, otation, and oil recovery to mention just a few), too little is yet understood about the parameters with which their stability can be controlled. Thus, the development of new products is often based on “trial and error.” In order to learn more about the properties of well-drained, dry foams, the investigation of the foam building blocks, i.e. the foam lms, is generally regarded as promising [1-4]. With respect to low molecular weight (LMW) surfactants, we usually distinguish between sterically and electrostatically stabilized lms. The former are called Newton black lms (NBFs), whereas the latter are referred to as common black lms (CBF) or common thin lms (CTFs). For the sake of clarity, we will solely use the abbreviation CBF (the difference between CBFs and CTFs is explained in Ref. [5]). The CBFs are relatively thick and water rich whereas the NBFs are thin lms with a very low water content.
