Improved microscopy method for morphological characterisation of pulp fines

It is widely accepted and discussed in the literature that not only fiber properties but also fines properties determine the final paper quality. While fiber morphology is well studied, morphological characterization of fines is usually restricted to the quantity of fines in a certain pulp since it is quite difficult to measure detailed morphological properties of the fines. They have a broad size range, a high surface area, show different optical properties within the fines fraction and are irregular in shape. In this article an optical method is introduced which allows the evaluation of differences in the morphology of fines. Quantitative information regarding particle size and shape can be obtained. The effect of optical properties on size measurement of different types of fines is minimized by a special sample preparation technique. The results of the new method are compared to those of a commercial flow cell based fiber analyzer. It was found that the flow cell analyzer failed in the detection of a large portion of fibrillar fines.