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.

Paper has a crucial impact on the qualitative properties of printed product as properties of the paper’s surface directly impact the ink transfer, consequently, basic optical properties of the print. Although same ISO paper type, papers possess variable surface properties leading to different influence on the ink transfer. The aim of this research was to analyse influence of the surface properties of the paper, including surface free energy, smoothness and gloss of some standard papers used in lithography on the ink transfer while matching the colorimetric values defined by ISO 12647-2:2013. Determination of amount of the ink transfer, optical density, mottling and colour difference of prints were performed to evaluate paper-ink interactions. Results have shown that produced prints differ in the investigated properties. Furthermore, there are significant correlations between the surface free energy of the paper and paper smoothness and the ink transfer. In addition, amount of ink used to produce a standardized print varies for different paper types (even in the same ISO paper classification), meaning difference in ink costs. This research proved the high influence of paper’s certain parameters on the ink transfer by strong correlation coefficients. This enables better process control and optimization of the printing.

Packaging plays important part of the visual communication and in consumer's choice of purchasing goods. To enhance visual appearance, packaging material is often coated. Beside enhancement of visual appearance, additional coating often improves other packaging properties. The COVID-19 pandemic stressed the importance of the antimicrobial properties of goods that encounter consumers. During purchasing, consumer first meets the packaging making it significant in the consumer's protection. The aim of this research is to determine antimicrobial properties of nanocomposite coating which includes nanosized TiO2. For the purpose of the research a set of offset cardboard prints was coated with nanocomposite coating composed of water-based varnish (WD) and nanoscale TiO2 particles. The prepared samples were characterized by determining CIE L*a*b* coordinates of primary colours (CMYK), detecting colour fading after the accelerated ageing process by density measurements and by determining inhibition of microorganisms' growth by using smear test.The change in chroma affected by UV radiation (accelerated ageing) is most visible on yellow samples while both, cyan and magenta proved to be more resistant to UV radiation. UV radiation did not cause significant change on the L* coordinate of black, although its values were affected with initial varnishing as TiO2 is also used as a white pigment. Although increase of the TiO2 concentration in nanocomposite causes increase of the colour change, only the one with the highest concentration (2%) proved to be unacceptable. On the other hand, as the beneficial effects of nanocomposites increase with increase of the TiO2 concentration, the nanocomposite with 1% of TiO2 should be the choice.