The influence of pollutants on accelerated ageing of parchment with iron gall inks

Moist heat (100 degrees C in closed vessels) and pollutants (SO(2)or NOx, 100 degrees C) techniques of accelerated ageingwere applied in stability investigation of iron gall inks on parchment. The measured characteristics onparchment samples coated with inks (made of iron(II) sulfate and gallic acid or tannic acid in variousratios) reflected their chemical, optical and spectroscopic attributes. Decrease of surface pH values wasmeasured for all samples, especially after ageing with SO2. The results obtained, comparing the non-agedsamples with those aged upon heat and pollutants, revealed the decrease of lightness L* and the increaseof chromatic coordinate b* for all six ink layers. These differences in b* were dominantly reflected in valuesof total color difference (Delta E* ab, CIE L* a* b*). The variations in UV/VIS reflectance spectra and Delta E* abevidencedthe considerable damage of inks exposed to accelerated ageing, especially for inks prepared with excess ofacid to iron. FTIR spectroscopic measurements of parchment showed that accelerated ageing procedurescaused changes in structure and arrangement of collagen, and the formation of oxidation products inparchment during the accelerated ageing was stimulated by presence of inks. EPR spectra of parchmentcoated with inks showed the paramagnetic signals of various Fe(III) species ions in different coordination. (C) 2013 Elsevier Masson SAS. All rights reserved.