Influence of selected sheet-fed offset printing conditions on primary mottling

The key parameter in the printing process is the evenness of applying the ink layer on the printing substrate. It determines the quality of the produced prints. One of the many factors affecting the final evenness of the ink layer on the print is the phenomenon of mottling, which is caused by the non-uniform internal structure of the paper. The aim of this work was to analyze the influence of basic printing parameters on the value of the mottling index. The research showed a significant effect of the pressure in the printing unit of the offset machine and the thickness of the ink layer on the printing substrate on the value of the primary mottling index. In addition, the research revealed that the properties of the printing substrate have a significant impact on the value and nature of changes in the mottling index. In this work, using the Fourier analysis, the frequency of optical density fluctuations in solid tone area related to the mottling phenomenon was also studied. No influence of pressure changes in the Nip of the printing unit on this print parameter was found.