Equilibrium Angle at the Surface of a Porous Medium

Is there a macroscopic contact angle between a liquid and a porous medium The answer is that an average contact angle e can be defined only in an equilibrium situation. To illustrate the point, when Jsl 7so it would make no sense to consider the contact between a dry porous material and a liquid since the liquid would instantly and irreversibly penetrate the porous medium. 

FIGURE 9.21. (a) Meniscus alongside a wet porous material (b) drop resting on a wet porous surface. 

That said, it is possible to define and measure an angle 9e There axe, however, cases where one may end up in a total wetting situation. 

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