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Understanding the influence of UV varnishing on diversified tonality spot colors is significant in offset printing process. Versatility of various spot colors implies repeatability and correct reproduction. UV varnishing methods, besides enhancing the visual impact on the product, have a protective role, but due to the effect on different wavelengths spot colors can cause negative colorimetric changes. The research examined the impact of UV varnishing methods on printed spot colors on diverse printing substrates. The degree of change on prints caused by UV varnish was determined using spectrophotometric and densitometric methods. Research results are clearly showing the modality and the extent UV varnishing method causes on spot colors. This paper presents objective conclusions that help predict possible variations in spot colors, as well as limit values of colorimetric deviations that may affect the quality of the reproduction process.

This study explores the applicability of micro- Raman spectroscopy as a non-destructive technique for the analysis of color toner printed counterfeits. The main aim of the research paper was to find out whether Raman spectroscopy is a suitable method for establishing the connection between different specimens of counterfeits suspected to be printed with the same toner on the same machine. Specimens of different types of toners printed on different types of paper are analyzed by means of the micro-Raman spectroscopy system with the excitation line at 514.5 nm. For each specimen cyan, magenta and yellow toners are analyzed separately. The yellow toners displayed the most distinctive Raman spectra. The results show that micro-Raman spectroscopy can be successfully applied as a method for the analysis of color toner printed counterfeits, such as banknotes and documents, in order to establish links between more or less different specimens of counterfeits by measuring the properties of a color toner.

There is often a phenomenon depending on dominant tones which results in the end users dissatisfaction with halftone color reproduction. This phenomenon is known as “metamerism” and it is the subject of research for many scientists. The metamerism on halftone color images with different dominant tones (blue, red, green and yellow) was researched in this paper, at the light sources D 50 , D 65 and daylight. The results of the objective and visual evaluation were presented on the basis of colorimetric measurement of the grey balance patch, by the means of MacAdam ellipsoids in three dimension CIE L * a * b * system. Both the metamerism index MI and the ellipsoid volume have also been calculated. This paper confirms that the metamerism of the halftone color images can be estimated by measuring CIE L * a * b * values of the grey balance patch and by calculating MacAdam ellipsoids.