The smoothness or roughness is a substantial surface property of papers, cardboard and cartons. The quality of the surface structure has a great influence on the printability and any form of coating. The Bekk smoothness is a method established in the paper industry based on air flow. The slower the air flows between the paper surface and the ideal plane, the higher the smoothness, expressed in the Bekk smoothness seconds. The shape, the total volume as well as the distribution of the cavities at the contact surface are decisive for the smoothness.

In contrast to PPS and Bendtsen, a representative paper area of approximately 10 cm² is tested in the Bekk method.