Wetting of Paper by Organic Liquids.

The measurements of contact angles on paper are disturbed by the roughness and the porosity of the surface. The wetting can be studied by measuring the volume or the depth of penetration since they are proportional to the square root of the cosine of the contact angle. Organic liquids varying in polarity form mineral oils to glycols have the same contact angle. It makes no difference whether the paper is sized or unsized. Since the contact angle of highly polar liquids may be presumed to be zero the wetting of paper by most organic liquids is almost perfect.