Effect of gravity on the apparent contact angles

The effect of gravity on the rough solid-liquid interface has been studied theoretically in the sessile drop method. Then, it was found that its interfacial tension is enhanced by gravity when gas is adsorbed at it. As a result, the apparent equilibrium contact angle, which is considered not to be influenced by gravity so far, can be raised by gravity for rough surfaces. The calculated dependence of contact angles on gravity under the ordinary conditions of the sessile drop method is large enough to detect by experiment.