ABSTRACT
Contact angle measurements are still most frequently employed for determination of the surface free energy of a solid material. This is because of their relative sim plicity. However, in fact, the determination of the so-called ‘Young wetting con tact angle’ is no longer an easy task. The appearing contact angle in wetting ex periments is often not well characterized because of insufficient precautions taken during its measurements, or because of the solid surface complexities of chemical nature (the energetic heterogeneity) and the surface roughness. Among others, these are reasons for the contact angle hysteresis H. It is defined as the difference between contact angle measured when the liquid front of the settled drop had ad vanced and the value obtained after it has receded, for example, by the liquid suc tion into the syringe [1].
