Bohuslava Havlínová

The stability of offset inks on paper upon ageing

The standard moist heat (80 °C and 65% relative humidity) and dry heat (105 °C) techniques of accelerated paper ageing were applied in stability investigations of offset ink films printed on alkaline offset paper. The measured characteristics of paper sample evidenced its first-class mechanical properties, large alkali reserve, in addition to high values of brightness and opacity. The pseudoplastic flow behaviour was established for original offset CMYK printing inks by rheological measurements. The results obtained, following application of both ageing procedures, revealed the significant exponential decrease of relative optical density for MAGENTA and YELLOW ink layers. The variance in visible reflectance spectra and in total colour difference ΔE* (L*a*b* CIE) of ink films evidenced the considerable damage of CYAN and YELLOW ink films, especially upon moist heat treatment. The differences in lightness ΔL* play the dominant role in ΔE* values of BLACK ink films upon both ageing procedures. The FT-IR spectroscopy was additionally used in the characterization of paper, inks, as well as ink films on paper before and after ageing.

Ink receptivity on paper — characterization of paper materials

Abstract The rheological behaviour of three black offset inks was tested using viscometer with the cone and plate geometry. The shear stress versus shear rate measurements confirmed that the investigated offset inks represent similar viscoelastic, pseudoplastic fluids, forming thixotropic structure. Mileage and ink transfer curves were measured onto the paper materials with different properties. The analysis of experimental results using Tollenaar–Ernst and modified Walker–Fetsko equations established the substantial role of the paper characteristics such as smoothness, brightness and penetration in the process of ink film formation on paper substrates during printing.

Impact of Stabilizing Procedures on Acidic Paper

Libraries and archives are confronted with progressive deterioration of their collections caused by paper degradation. We present a single-step treatment for acidic wood-pulp papers that includes a) removing soluble acidic products causing acid hydrolysis; b) preventing oxidative decay by introduction of an antioxidant agent; c) neutralizing free acids present in paper and forming an alkaline reserve to inhibit paper ageing; and d) improving mechanical strength by application of cationic starch. Zusammenfassung/résumé at end of article received: 13.10.2011 revised: 28.02.2012 179 DOI: 10.1515/res-2012-0008 ˇ ˇ

Influence of Deacidification on Arylmethane Dyes on Paper

Abstract The deacidification of historic paper objects has evolved into a method that is applied in mass-scale in some archives and libraries. While the impact of the deacidification reagents on paper is quite well researched, knowledge about the behavior of colours and dyes is more limited. Our study focused on the influence of paper deacidification by the Book Saver® process on eight different dyes applied on paper, as well as on the paper support itself. Accelerated ageing in moist and warm conditions (80°C, 65% relative humidity) was applied to investigate the stability of the dye layer on top of the paper, with respect to their chemical, optical and spectroscopic attributes. The Book® deacidification process increased the pH of the aqueous extract and an alkaline reserve was created. FTIR spectroscopic measurements showed that deacidification suppresses acid hydrolysis of paper. The variations in UV-Vis reflectance spectra and in total colour difference of the dye layer evidenced the changes in the structure of dyes caused by accelerated ageing, but the extent of the changes differs depending on the dye. We can conclude that some dyes are more prone to changes by deacidification than others.