Air-induced paper discoloration is described as being different from other discoloration morphologies. It seems to be the result of prolonged exposure to air in a humid and polluted environment without appropriate protecting coverage. In this work, three folios from the same eighteenth century book, presenting three degrees of discoloration and opacity and subjected to different environmental conditions, were examined and compared. Samples were analyzed and compared by three different instrumental techniques, mid-infrared spectroscopy, X-ray fluorescence (XRF), and scanning electron microscopy (SEM). Chemical and physical changes were confirmed from the data collected by these techniques. The absence of the secondary amide band characteristic of proteins in the infrared spectra of the two discolored folios, accompanied by the appearance and increase of white mineral-like deposits visible in the SEM micrographs, support the idea that oxidation reactions occurred and that these two folios were subjected to more severe degradation hazard.
Adriana Ferreira, Francisca Figueira, Sofia Pessanha, Ingelise Nielsen, and Maria Luisa Carvalho, "Study of Air-Induced Paper Discolorations by Infrared Spectroscopy, X-ray Fluorescence, and Scanning Electron Microscopy," Appl. Spectrosc. 64, 149-153 (2010)