On the roughening effect of laboratory heatset offset printing on SC and LWC paper surfaces

The structural effects of water and ink application on the paper surface during laboratory heatset offset printing are presented. The roughening effect of water was clear on supercalendered (SC) paper while no significant effect was detected on lightweight coated (L WC) paper surfaces. Although the ink levelled the microsurface of both SC and L WC papers, the macrosurface structure of SC paper suffered a considerable roughening due to the water application. Both the surface pore volume and the facet orientation are suitable parameters for characterizing the surface structure affected by the ink. The facet orientation is also a most relevant parameter for estimating the gloss level of paper and prints. The variation of such facet orientations may also give a suitable prediction of the paper surface gloss variation. Based on this assumption, it was found that the local gloss variation of LWC paper decreased after printing. The opposite effect was found on SC paper, although the gloss level increased for both paper grades.