Dependence between paper properties and spectral optical response of uncoated paper
Abstract This paper presents a method to describe, with good accuracy, the relation between variations in paper properties and variations of the spectral optical response of an uncoated paper. The dependence between density, filler content, grammage, and the spectral optical response is characterized by a multivariate model. The model is based on large-scale measurements data on a set of paper samples that have been produced with different values of grammage, density and filler content, representing the variations within a normal 80 g/m² uncoated paper. From the optical measurements the light scattering (s) and light absorption (k) coefficients have been estimated according to the Kubelka-Munk theory. The results from this study will give valuable input to optical modeling activities, where the optical variations are predicted from measured small-scale variations in underlying paper properties. The variations in the paper properties can be used to model the light scattering coefficient, s, but there were too small variations in the light absorption coefficient, k, to find any significant dependence to the paper properties for the samples studied in this work. Furthermore, linear models give sufficient accuracy in the intervals studied. Additional findings from this study are the different effects of wet-pressing and calendering on the light scattering coefficient.