Even in these challenging times, cardboard packaging industry is increasing its revenue with stable annual increase prediction, but customers are increasing demands on the packaging with respect to environmental protection, attractiveness, and branding. This article aims to determine the influence of image processing in terms of gray component replacement and overprint varnishing on the color reproduction on a cardboard packaging material. A test chart with tertiary colors was defined and modified by different gray component replacement levels. It was printed in accordance with ISO norm on coated and uncoated cardboard and finished by overprinting water based, offset, and UV varnish. The prepared samples were evaluated by measuring surface coverage, tone value increase (dot gain) of primary colors and calculating ΔE00 of defined tertiary colors. The results showed that gray component replacement application reduces ink consumption. Higher gray component replacement applied results in lower ink surface coverage, but the decrease is also dependent on the image content. The TVI (dot gain) is significantly influenced only by applying UV varnish, resulting with higher TVI. The color differences of the tertiary colors showed that increased level of the gray component replacement applied did not cause significant color differences, even decreased color difference in some cases. Additionally, applying gray component replacement decreased color differences in “reddish” part of the gamut. This research proved that lowering the ink consumption due to the gray component replacement will not cause significant differences in the color reproduction. Furthermore, varnishing with commercial offset or water‐based varnish will not cause higher deviations in color reproduction, but use of the UV varnish would.

In this research study, the applicability of polycaprolactone‐silicon dioxide and polycaprolactone‐zinc oxide coatings used as primers on papers for offset printing, was analysed. Polycaprolactone nanocomposites with different concentrations of nanoparticles were prepared and coated onto three types of papers: uncoated, low‐coated and gloss. The main aim was to analyse the influence of the nanoparticle concentration in primer on the optical and colorimetric properties of cyan and magenta offset printed samples. To further evaluate the applicability of the primers, the tensile strength of primed samples and their surface properties were analysed. Results show that prepared primers are primarily applicable on uncoated and low coated papers. Both nanoparticles in specific concentrations increased gloss values for printed samples on low‐coated paper, and the addition of both types of nanoparticles increased the rub resistance of printed samples. Furthermore, for each type of nanoparticle, the optimal concentration at which the colour deviation on print was minimised could be defined. Adding nanoparticles to primers did not significantly improve mottling on cyan‐printed samples. However, by increasing the concentration of nanoparticles in the primer by up to 1%, the mottling on magenta‐printed samples decreased.

UV radiation or sunlight can affect the printed sample by fading the ink surface and therefore the product losses it's decorative purpose and becomes less desirable to the customer. To create the efficient protective coating, titanium dioxide (TiO2) will be used as a well-known compound that should lower the effects of UV radiation. TiO2 should lower the colour fade after UV radiation and this will be determined by densitometric and colorimetric (CIE L*a*b*) measurements. In addition, measurement of print gloss will also be conducted to evaluate visual appearance of the sample. Biopolymer Polycaprolactone (PCL) was the base of the PCL-TiO2 composite in which TiO2 nano sized. To determine influence of the amount of TiO2, three composites were prepared by adding different weight ratio of the TiO2. The prepared nanocomposites were then applied onto the offset prints on gloss art print paper and on the uncoated paper. The results have shown that TiO2 coating does affect ink’s density, colorimetric properties and print gloss after initial coating. The change in chroma due to the accelerated ageing is most visible on yellow ink, cyan and magenta proved to be the more stable. Accelerated ageing caused change in the L* of black. On all colours, increase of the TiO2 weight ratio improved resistance of colour to change. Coated gloss paper was more resistant to density change where uncoated had lower change in chroma. It could be concluded that TiO2 has the ability to protect the prints in the measured time interval but it has to be noted that concentration of the TiO2 particles also causes colour difference and must be observed when defining composure of the nanocomposite.

Thermochromic (TC) printing inks change their colouration as a response to a change in temperature. This ability renders them attractive for various applications such as smart packaging, security printing, and marketing, but their application is limited due to their low UV stability, i.e., loss of their thermochromic effect when exposed to UV radiation. In order to improve the UV stability of TC prints, one offset TC printing ink was printed and coated with nanomodified polycaprolactone (PCL) coating. The coating was prepared with the incorporation of 1%, 2%, and 3% mass ratios of ZnO and TiO2 nanoparticles in the PCL matrix. The prepared nanocomposite coatings were applied onto the TC print and exposed to UV radiation; afterwards, they were characterized by the colour properties of prints, SEM microscopy, FTIR, and fluorescence spectroscopy. SEM microscopy, FTIR, and fluorescence spectroscopy showed higher rates of polymer degradation, and the results of colour stability indicated that 3% TiO2 in PCL matrix gave the best UV stability and protection of TC prints.

The porous structure of the aluminium oxide surface of lithographic printing plate (PP) has a most significant influence on the quality of the imprints. This study presents the results of application of electrochemical impedance spectroscopy (EIS) in characterization of PPs' porous structures and their changes during chemical processing. Two common PP types-thermal and conventional-were investigated. The influence of the processing solution's working age on topographical changes of PP surface and associated change in the impedance spectra are investigated and discussed. The equivalent electrical circuit models reproducing the observed EIS spectra are proposed. Based on these models two mechanisms of surface's topography changes responsible for degradation of PP performance due to the processing are identified and discussed.