Effect of grey component replacement processing and varnishing on the light fastness of colours on cardboard prints

Abstract The visual appearance of packaging is one of its most important features. Electromagnetic irradiation causes a change in colour and often leads to colour fading (ie, to diminished visual appearance of a printed product). This research study aimed to determine the combined effect of grey component replacement image processing and varnishing on the protection of prints' appearance when exposed to accelerated ageing. For that purpose, two test charts were printed in a lithographic press and coated with water‐based and ultraviolet‐curable varnish before exposing them to xenon light. The prepared prints were evaluated by determining the tone values and colour difference, as well as the rub and abrasion resistance. In addition, Fourier Transform–infrared‐attenuated total reflectance spectra were recorded to detect possible chemical changes caused by the (AcA). The results showed that the investigated period of (AcA) caused significant differences in the tone values of yellow, while the other primary colours proved to be more resistant. The water‐based varnish provided better protection than the ultraviolet‐curable varnish. The grey component replacement image processing diminished the colour difference caused by (AcA) on all the prepared print samples, and was particularly detected in tertiary colours containing the mid‐range tone values of yellow (34%‐68%). Both varnishes improved the rub resistance of aged prints, but only ultraviolet‐curable varnish improved the abrasion resistance of both the unaged and the aged prints. In conclusion, applying varnish to prints ensured enhanced rub and abrasion resistance and diminished the colour change caused by (AcA). Finally, improved resistance to colour change was achieved by processing images with the grey component replacement method.