Local Orientation of Flocs in Paper

Abstract

So far little attention has been paid to the orientation of flocs in paper sheets . It can be measured by means of an image analyser and the two-dimensional Fourier transform. The principal direction in the power spectrum of a paper in transmitted light is a measure of the floc orientation.

It can be shown that the coefficient of correlation between fibre orientation (Lippke – Tester) and floc orientation amounts on average to 0.7, when profiles across the web are taken into account. Papers, particularly those which are made on hybrid formers, show a two-sidedness concerning floc orientation and anisotropy . The orientation has no significant effect on the uniformity of formation but determines the orientation of cockles. The power spectrum of the local orientation of a paper seems to be very useful in the detection of deterministic variations in orientation, which are invisible in light transmission images.