In the papermaking industry, cellulose fibers often undergo a bleaching process which affects the surface of the fibers, or their overall morphology. The surface of the produced paper, which is most often used as a printing substrate, depends on the production method, the arrangement of the cellulose fibers, and the quantity and fineness of the filler. The micro-irregularities caused by the uneven distribution of fibers and surface particles of the filler make the paper’s surface rough and affect the print quality and its stability when exposed to light from the moment of production to use. The unbleached cellulose fibers in the printing substrate contain natural pigments, lignin and hemicellulose that absorb UV radiation, as opposed to bleached fibers, which have higher whiteness and lightfastness. Therefore, the influence of UV radiation on the surface roughness of prints made on papers with natural unbleached and bleached hemp fibers was analyzed. This research confirmed that papers formed from unbleached fibers have rougher surface and that printed graphic products from bleached fibers have higher stability to UV radiation than those from natural, unbleached hemp fibers after 96 h of treatment in the Suntest chamber.

Packaging and labels are used for a variety of products and have become an indispensable part of daily life, while products without labels or packaging cause uncertainty among consumers. The global trend is to reduce the amount of packaging waste by recycling and reusing the same material or using other available waste raw materials. With large quantities of stalks remaining discarded in the fields after harvest each year, cereal straw is emerging as an alternative source of lignocellulosic fibers for secondary green packaging and labels. In this study, the usability of printed papers with discarded lignocellulosic fibers by offset and gravure printing processes for secondary green packaging and labels was observed based on the qualitative parameters of reproduction and ink penetration into the printing substrate. From the obtained results, it can be concluded that gravure prints have greater penetration of the ink into the printing substrate, resulting in more uneven surface coverage with printing ink, compared to offset prints, where the viscosity of the ink and the printing process itself have the greatest influence. Therefore, these substrates with discarded lignocellulosic fibers can be used for secondary green packaging and labeling printed by the offset printing process, while gravure printing requires an additional coating or a larger amount of filler in the paper structure.

This paper proposes a method for changing pixel shape by converting a CMYK raster image (pixel) to an HSB vector image, replacing the square cells of the CMYK pixels with different vector shapes. The replacement of a pixel by the selected vector shape is done depending on the detected color values for each pixel. The CMYK values are first converted to the corresponding RGB values and then to the HSB system, and the vector shape is selected based on the obtained hue values. The vector shape is drawn in the defined space, according to the row and column matrix of the pixels of the original CMYK image. Twenty-one vector shapes are introduced to replace the pixels depending on the hue. The pixels of each hue are replaced by a different shape. The application of this conversion has its greatest value in the creation of security graphics for printed documents and the individualization of digital artwork by creating structured patterns based on the hue.

Due to the rising problem of deforestation, slow renewability, and higher cost of wood sources, it is of great importance for the paper and packaging industry to find suitable, environmentally friendly alternative sources of cellulose fibers. Much of the research has focused on studying the use of non-wood sources from various annual or perennial plants from which cellulose fibers can be obtained with equal quality to those from wood sources, since they are a fast-growing, renewable, and cheap source of fibers. This research focuses on the laboratory production and stability valorization of a paper substrate for packaging containing virgin fibers from triticale straw mixed with recycled wood pulp in various amounts up to 30%, printed with black ink through a simulation of the offset printing technique under controlled conditions. For stability analysis, printed paper substrates were subjected to three treatments essential for packaging: aging, rubbing, and chemical treatment. The stability of the prints was evaluated after treatments though spectrophotometric measurements (ΔE*_ab, ΔR, ΔL*, Δa*, Δb*) and Fourier transform infrared analysis. The aging, rubbing, and chemical stability of the prints with the addition of triticale virgin fibers was improved for all product packaging except for products containing soybean oil.

The drying process of printing ink on absorbent substrates in conventional printing techniques essentially takes place in two steps: the penetration of the ink within the printing substrate and the oxidation or oxy-polymerization process. The process of ink penetration within the printing substrate itself begins immediately after the ink is transferred using the impression cylinder, while the oxidation or oxy- polymerization process lasts up to several hours. In this research, the correlation between the value of ink penetration within the printing substrate and the print-through effect on prints produced using three different printing techniques was observed. In this analysis prints made on sustainable printing substrates were produced with a 30% share of non-wood cellulose pulp were observed in order to reduce the consumption of wood raw materials worldwide. The results of the research prove that the degree of ink penetration within the printing substrate correlates with the print-through effect in all analysed black prints (printed with one ink layer), while no correlation was found in the prints that were printed with three ink layers (cyan, magenta and yellow). That is the print-through effect is very low compared to the values obtained for ink penetration within the printing substrate. It was also found that the lowest values for ink penetration inside the printing substrate was achieved with offset printing process, and thus the lowest values for the print-through effect. Sustainable printing substrates achieve very low deviations compared to reference substrates made only from recycled wood pulp, which confirms the possibility of using these substrates for both secondary packaging and publications.