Practical Control of Foamability and Persistence

The addition of surfactants and/or polymers to a foaming system can alter any or all of the above-mentioned system characteristics and therefore enhance the stability of the foam. They may also have the effect of lowering the surface tension of the system, thereby reducing the work required for the initial formation of the foam, as well as producing smaller, more uniform bubbles. 

For a liquid to produce a foam of any degree of utility, it must be able to 

The fundamental impact of surfactant concentration and diffusion rate in lamellar films can be viewed roughly as follows (Fig. 12.6) as the lamellar 

FIGURE 12.6. The microscxjpic anatomy of a foam. The complex interplay of interfacial and hydrauhc forces makes the understanding and control of foams a challenging proposition. The effective control of those interactions with surfactants or other additives determines the persistence of a given system. 

Quantitatively, the Gibbs effect can be described in terms of a coefficient of surface elasticity E, which Gibbs defined as the ratio of the surface stress to the strain per unit area 

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