4. Surface rheology

4.1 Definition

Surface rheology is much less well known than classical volume rheology, as it is more difficult to study. Recently, new commercial devices have become available on the market, and this type of rheology is about to become more familiar. What's it all about? Let's imagine we're shearing a system of two superimposed liquid phases: the response will sometimes be the sum of the responses of each liquid layer, sometimes greater than this sum. The difference between the two, called "excess" by Gibbs,...