A Study of the relationship of Sheffield & IGT methods for determining paper smoothness and their ability to predict gravure printability

A variety of methods have been devised for the measurement of the smoothness of paper. These are reviewed and summarized in this work. Of the available methods, two of the most widely used have been selected for study. The air-leak method exemplified by the Sheffield instrument, and the nip-spreading method of the IGT printability tester are specifically presented and performed. The data obtained in empirical experiments are statistically analyzed and plotted, so as to determine if there is a functional relationship between the responses of these two methods. A linear relationship between the two is shown to be an appropriate model. This paper also indicates the predictability of gravure printing quality on the basis of paper smoothness/roughness. The percentage of missing cells of the gravure prints are shown to be related to both forms of smoothness/roughness measurement. 78% of the gravure cell skipping data variation as printed by the IGT printability tester is attributable to smoothness/roughness measurement. The remaining amount of variation is associated with error or untested factors. Compressibility and oil absorbency of paper should be further studied and incorporated into similar studies. It is expected that the addition of these variables would improve laboratory prediction of gravure printability as defined by cell skipping