ABSTRACT
A distinction should be made between hysteresis of dynamic contact angle and static one appearing in the case of a liquid drop on a smooth solid surface. The zero value of the difference means that the liquid film possesses properties of a duplex film and experimental receding contact angle should be zero. Interesting information on the wetting properties of a solid surface can be derived from measured advancing and receding contact angles of a liquid; the contact angle hysteresis is due to the film present behind the drop after the three- phase contact line has retreated. To calculate the receding contact angle, the solid surface free energy components and the liquid surface tension must be known. For many solid/liquid systems the apparent receding contact angle can be calculated if the appropriate wetting film is taken into account.
