Roughness Bendtsen (ISO 8791-2):
|What||A measure of the rate at which air will pass between a flat circular land and a sheet of paper or board when tested under specified conditions and at an operating pressure.
It is expressed in millilitres per minute.
|Why||A rough surface has impact on printability: it may cause dot gain, as a result of which less detail is visible in the printing image.|
|How||Clamping a test piece between a flat plate and a circular metal land on a Bendtsen tester. Supplying air at a nominal pressure of I,47 kPa to the space enclosed inside the land and measuring the rate of air flow between the land and the test piece. The higher the measured value, the rougher the surface.|
|Calculation||Report the average of 10 significant values and the standard deviation of both front and back.|
|Note||This method is mainly accurate for uncoated substrates that have had no special calender treatment.|