PARTITIONING FORMATION INTO ITS COMPONENTS

摘要

Commercial formation instruments which have been available give a single number as an index of formation, a measure of how much local nonuniformity of formation there is. These instruments are blind to the spatial distribution of formation nonuniformity and therefore to scale of formation.rnEarly works by Norman and Wahren [1-2] and Wrist [3] introduced frequential analysis for studying paper structure. Using our adaptation of 2-D Fourier transform analysis, the McGill authors have developed the approach of partitioning formation nonuniformity into its components as a function of scale of formation from about 0.5mm to several centimeters, the recognized range for formation. The formation is quantified over this range of scale of formation. This constitutes the "components of formation", one component for each value of scale of formation.rnAs properties of paper, not its formation, generally determine product quality, intensive effort was devoted over several years to determine, for various paper properties, various grades of paper from many paper machines, which component(s) of formation are important and which are not, and for those that are important, what is the sensitivity of that specific property to controlling formation components. It was shown that various paper properties are typically sensitive to the components of formation over some specific range of scale of formation, but are insensitive to formation components outside that range of scale. Furthermore, it was documented how changes in papermaking parameters affect very differently the components of formation at different scales of formation. Thus the components of formation constitute the intermediate variable between papermaking parameters and paper properties.rnIt was established that the print quality of uncoated offset paper, printed commercially on a Heidelberg press, is controlled by components of formation in the range 4-8mm scale of formation, while components at values of scale smaller or larger than this have little effect [4]. Over 4-8mm scale of formation, the print quality - components of formation correlation is strong, R2 0.56, about double than that when formation was measured by several single-number formation index