Impact of the Paper Degradation State and Constituents on Its Behavior During and After X-ray Exposure

Abstract

Paper is a complex biopolymer material which contains papermaking additives and often bears inks and other graphic media. Cultural heritage paper-based artefacts are most often deteriorated to some extent. This research explores how intrinsic factors such as constituents and degradation state can impact the modifications incurred in aged papers during and after X-ray examination. To this end laboratory model papers, artificially aged, and 18th and 19th century archival documents, with and without additives (gelatin, calcium carbonate) and iron gallate ink, were exposed to Synchrotron X-ray radiation at doses that were previously shown to incur damage in unaged cotton papers (0.7 to 4 kGy). Glycosidic scissions, hydroxyl free radicals, UV luminescence and yellowing were measured immediately after the irradiation, and were monitored over a period of three years. The depolymerization of cellulose was lower in the aged papers, as well as in the papers containing calcium carbonate and gelatin, than in the unaged fully cellulosic papers. Compared to the papers with no additives, there were more hydroxyl free radicals in the papers with calcium carbonate and slightly less in the gelatin sized papers. UV luminescence and yellowing both appeared post-irradiation, with a delay of several weeks to months, while the intensity of the responses was impacted by the various paper constituents. The papers with iron gallate ink showed limited degradation in the low doses range, most probably due to recombination of the free radicals produced. Doses below 4 kGy did not cause yellowing or UV luminescence of the archival papers within the whole monitoring period. At higher doses (26 to 36 kGy), a slight UV luminescence appeared after 21 months, as well as a slight yellowing after three years, in some of them. No clear correlation between the degradation induced by the irradiation and the constituents in the paper nor its conservation state could be made. The archival papers in good conservation state depolymerized to the same extent as the model papers, while the most degraded archival papers were less impacted than the latter.

Biopolymer applications for different treatments of the historical paper manuscripts and leather bindings: A Review

“…It was used as a binder with filler mixed with cellulose powder, acacia arabica, and clay nanoparticles to fill small holes in the bookbindings [91]. It was used as re-sizing on iron gall ink corrosion on a fiber that was previously gelatin-sized, gelatin delays the degradation of cellulose as Iron is chelated by gelatin that forms a gel during cooling and retaining iron, thus the concentration of iron inside the fiber is lowered [12]. There are some disadvantages to gelatin when it is used for consolidation such as: supporting microorganism growth in high relative humidity, attractive to insects, becoming brittle under excessively dry conditions and it is degraded by ultra-violet light and yellows with age, additionally, the low grades of gelatin contain metallic salts and other impurities ( [44].…”

“…Historical Papers are made of plant fibers, which contain cellulose, and sometimes contain hemicelluloses and lignin [10,11]. There are fillers, Additives, and sizing, which are usually added to writing to enhance usability such as reducing water permeability and brightness [12]. Leather is a protein structure based on the collagen fibril made of animal skins such as goats, and calves [6].…”

The use of X-ray computed tomography and X-ray fluorescence in research into historical printing from the 17 th century

“…Changes at the macromolecular level began to manifest themselves at doses higher than 1 kGy. Surprisingly, historical paper was shown to have a higher resistance to Xrays than modern archival paper [4]. In the National Library of the Czech Republic, tests were carried out on the effect of Xrays on paper at 120 kV voltage and 0.3 mA current with Xray tube distance of 790 mm from the detector, paper was placed near to the detector.…”