Surface for contact angle measurement

Preparation of clean surfaces for contact angle measurements... 

The intrinsic surface properties of a material can only be investigated if the surface is clean at a molecular level. It is likely that a large body of information on surfaces which has been obtained and reported in the literature is misleading because the measurements have been made on surface contaminants. Extreme care must be taken in preparing surfaces for contact angle measurement. For the calculation of thermodynamic parameters it is the equilibrium contact angle of a liquid on a surface which is of interest. In order to obtain a meaningful result on a planar surface the surface must be as smooth as possible and free from contamination. 

---