The Permanence of Conventional and Digital offset Prints

The permanence of prints depends on its components and on the influence of the external factors. The determination of prints on ageing contributes to the tehnological conditions of paper manufacture ( characteristic of the used rew materials, condition of pulp preparation, method of beating, sizing procedure, type of sizing agent), the techniques of printing and kind of printing inks, effects of lightining, temperature and atmospheric humidity, and the impact of microorganisms and moduls.in prints degradations the following processare included: oxidative degradation, alkaline hydrolysis, thermolysis, physical- mechanical demage and reactions to modul. In this work the test form is designed from the standard patterns composed of 210 fields of different combinations of colour values of subtractive analysis, generated by vector graphics in the steps of 5%. The same printing form was used for printing in the tecniques of conventional and digital offset printing. While in the conventional offset the modul inks with different ratio of renewable raw materials were used. Uncoated paper of 100g/m2 grammage was used in printing. The prints were submitted to natural and accelerated ageing. In application of the Color Open the conversion was done from CIE XYZ into CIE L*a*b*, in order to enable the construction and presentation of the print gamut in the three- dimensional unified space. The differences among particular gamuts of the printed samples in relation to the printing techniques, composition of the conventional offset ink and ElectroInk are presented in the work. The influence of the natural and accelerated ageing of prints on their optical stability is discussed. The work is in scientific sense the contribution to the explanation primarly of the influence of the printing technique and colour composition on the optical stability of prints.