Colorimetric changes of waterbased flexographic ink printed on hemp-based papers exposed to artificial ageing

Abstract

The objective of the research was to investigate colorimetric changes of the waterbased flexographic ink printed on hemp-based papers subjected to artificial ageing. Three types of commercially available hemp office papers were used as printing substrate and by Esiproof instrument were printed manually in full tone with process waterbased flexographic inks. Both, papers and prints were exposed to artificial ageing in the Suntest XLS+ test chamber according ASTM D 6789-2 standard. The L∗, a∗, b∗ colour coordinates were measured and ΔE00 colour difference was calculated for different stages of light exposure in order to determine the change from the original color value. In total exposure time was 96 h. The results have shown how the paper optical stability is dependent upon manufacturing process and that bleached hemp fibers provides better optical stability of papers than unbleached hemp fibers. Further, stability of prints made on hemp-based papers is for the most part defined by ink color, while the impact of the printing substrate is less pronounced. Generally, it was noticed how the most stable among prints were prints covered with the black ink, while prints with the yellow ink had the greatest changes in color under the influence of light.