Changes in the gloss of oxidatively dried offset prints during the drying process

Abstract

In this article, we examine the changes in the gloss of offset prints after printing. At the moment of printing, the ink transfer occurs under the influence of the pressure force and several processes are initiated simultaneously: the ink is absorbed into the print medium, and the ink begins to crosslink under the influence of oxygen in the air. The ink is applied to the print medium while still wet and reflects the light radiation falling on it differently than the already dried ink. The aim of our study is to find a correlation between the change in surface gloss and the drying process of the printing ink. During the test prints, we used oxidatively dried printing ink and two paper-based print media with different structures, absorbent offset paper and glossy art paper with a coated surface. For both types of paper, measurements were made immediately before printing, immediately after printing, and in the hours and days that followed. The measurement results and their evaluation confirm that the surface gloss of the prints changes as a function of time. The drying time, the gloss change, and the formation of the cross linked structure are influenced by the storage conditions. In the case of absorbent paper, the printing ink loses its surface gloss, while in the case of non-absorbent paper, the gloss increases during the drying process, since the ink film dries on the surface of the print medium, and the formation of the cross-linked structure also takes place here.