STUDY OF PRINTABILITY OF INDIAN NEWSPRINTS

Abstract

In the present work the variation in total ink transfer and transfer parameters and their effect on print—ability of Indian newsprints with changing printing speed • and pressure are studied. The total ink transfer increases with increasing printing pressure and decreasing printing speed;however the amount of ink immobili—zed by the stock as determined from the transfer parameter,b,does not parallel the trend in total ink transfer. The fracton . of ink transfer associated with the calculated split of the free ink film,f,includes both the ink transferred during decompression as well as the ink split toward the paper. The extent of ink penetration during paper compression in the nip decreases rapidly with increasing printing speeds. The printing smoothness,k,of the newsprints is described by an exponential distribution function relating the area contacted to the ink film thickness on the printing disc. It increases with increasing printing pressure. The print density calculated from the optical contrast between the unprinted and printed part of the sheet, increases with increasing the amount of ink on the printing disc. An increase in amount of ink on the disc to enhance the print density:. has an adverse effect on print through, Print- through; the undesirable property of the print being visible from the . - _ reverse side of print increases with increasing amount of ink on the printing disc. In the present work it is broken down into two additive components; direct show-through and print-through due to pigment penetration. The uniformity of print density is determined by the optically covered area. The optically covered area is independent of intrinsic luminous reflectance factor of the paper. The use of concept of optically covered area to describe the optical effect of the ink distribution over the printed area is discussed.