A pH method is described for the detn. of the wettability of membranes used in membrane distn. modules. The wettability factor that varies 0-1 is defined. With aq. EtOH, effects of dynamic overpressure and membrane stretching are shown to affect pore size and wettability of flat membranes. By this technique, the EtOH concn. for onset of membrane wetting (with Durapore 0.22 mm membranes) is 180 g/L as compared with the 235 g/L for penetrating-drop method. [on SciFinder (R)]