A METHOD FOR OBTAINING A LOCAL DENSITY VARIATION IN A SHEET

Physical and mechanical properties of paper are influenced by the state of aggregation of the composed fibers. In this study, a method for detecting a local density variation in a sheet has been proposed. In order to calculate sheet density at a particular spot in a paper, the thickness and basis weight of the spot must be obtained simultaneously. The newly developed device equipped a linear variable differential transducer first scans along a line in a sheet for detecting a thickness variation profile; variation in basis weight on the line as a function of transmitted light intensity through the negatively developed x-ray films from a light beam is then obtained. By computer division of basis weight by thickness, local density variation is calculated. This method is applicable to the characterization of paper since a local density variation profile reflects its paper-making process.