PPS-Roughness (µ) ISO 8791-4, 1,0 Mpa
A paper surface topography is characterised by the fibres and fillers and the intermediate pores, such a surface is never so even or smooth like a glass plate; to characterise this topography in a simple way we measure the pps-roughness by measuring the air flow on the surface of a paper sheet, similar to a porosity measurement, not in z-direction but in x- and y direction.
The measurement is done with a defined measuring device, with defined pressure of the measuring facility to the paper surface and with a defined rubber plate on the contrary paper side, the resulting values are calculated from pressure differences and describe the width of the slit which enables the air to pass between the measuring facility and the paper surface in x-y direction.