Contact angle measurements are affected by surface roughness; the effect depends on the abruptness of the microscopic features. Smoothly undulating surfaces as well as typical machined or polished finishes have little or no effect on contact angle measurements. Very rough surfaces such as those created by sandblasting or other abrasive processes will show a greater effect. In all cases, as long as one is comparing surfaces of similar roughness, it is the chemical composition of the surface that has the greatest effect on contact angles.