Capillary Attraction and Hysteresis of Wetting

Abstract Capillary attraction between two parallel plates partly immersed in a liquid is calculated, using changes in free energy as criterions. Because, when the equilibrium contact angles are different from 0°, hysteresis of wetting occurs as a rule, it is supposed that the 3-phase lines are not shifted when the plates move (for a small distance) apart or toward each other. When the two plates are identical and their mutual distance S is small, they should attract each other. When they are different and the equilibrium contact angle is obtuse at one, and acute at the other plate, then, at small S, repulsion is expected.