Critical point wetting

It is shown that in any two-phase mixture of fluids near their critical point, contact angles against any third phase become zero in that one of the critical phases completely wets the third phase and excludes contact with the other critical phase. A surface layer of the wetting phase continues to exist under a range of conditions when this phase is no longer stable as a bulk. At some temperature below the critical, this perfect wetting terminates in what is described as a first-order transition of the surface. This surface first-order transition may exhibit its own critical point. The theory is qualitatively in agreement with observations.