The quality of a printed image is strongly influenced by the physical and the chemical interactions between the ink and the paper. Print quality can be evaluated either by objective measurements using instruments or by visual assessment studies involving panel of observers judging the final print. In this article, the print quality on commercial papers as well as on non-commercial papers with different amounts of salt for surface fixation has been studied. Perceived detail reproduction depends not only on sharp edge definition but also on the level of color saturation (Chroma). Color saturation and edge definition originate from two different ink and paper interaction processes. Color saturation is heavily dependent on ink penetration while edge definition correlates to ink spreading. In order to gain understanding of the performance of surface treatment by salt, large efforts have been put on splitting up of the increase in color saturation (Chroma) and improved edge definition. The printouts have been made with a desktop printer using pigmented inks. Cross section images have been taken with a light microscope to analyze the ink penetration depth. SEM analysis has been made to analyze the aggregation of the pigments on the surface. The print quality measurements have been both objective measurements such as print density and subjective image evaluation using a test panel of observers in a perceptual study. The perceptual study focused on detail reproduction, and efforts were made to separate the influence of the print density from the edge definition on the detail reproduction. The result from this study shows that an increased level of salt as surface fixation improves the detail reproduction due to aggregation of the pigments on the surface and that the ink penetration depth can be reduced by adding salt as surface fixation resulting in a higher print density.
Jonas Örtegren, Ole Norberg, Anna Lundberg, "Aggregation of Color Pigments by Surface Fixation Treatment" in Journal of Imaging Science and Technology, 2011, pp 50605-1 - 50605-8, https://doi.org/10.2352/J.ImagingSci.Technol.2011.55.5.050605