Smoothness according to Bekk

Bekk smoothness is a method for characterising the surface topography of smooth paper or films with a roughened surface. The measuring principle is based on the fact that the surface to be characterised is placed on a flat glass plate with a hole. A vacuum is created over the bore, which sucks the sample surface onto the glass. The time for the vacuum decrease between 2 defined pressure points is measured. The method is not suitable for very rough and porous materials and very smooth plastic films.