The Development of Print Density and Print Through in Newsprint

Samples of the same newsprint were calendered to different roughnesses and porosities. Solid images were printed under constant press conditions with different amounts of a non-drying, oil-based inks. Print density decreased with increasing roughness and porosity. The reduction was caused by the non-uniform thickness of the ink film as it filled the surface depressions of the paper, and by the distribution of pigment in the z-direction of the paper. The condition worsened as vehicle oil penetrated further into the sheet. More ink was required by the rougher sample to attain the same print density as the smooth sample. Therefore, more pores were filled by vehicle oil and the rough sample suffered a greater loss of sheet opacity and had a higher print through. Extraction of the vehicle oil from the prints showed that oil penetration caused over 60% of the print through of the samples. print through first decreased with time, then increased, and finally decreased again due to sheet compression and recovery during and after printing, and to the penetration and redistribution of vehicle oil in the sheet. The literature on the effects of the structural properties of newsprint on the optical properties of solid prints is examined.