ELECTRON SPIN RESONANCE STUDY OF PAPER SAMPLES DATING FROM THE FIFTEENTH TO THE EIGHTEENTH CENTURY

Electron paramagnetic resonance spectroscopy is used to detect paramagnetic impurities in differently degraded antique sheets of unprinted paper. Impurities consist primarily of transition metal ions (Fe3+, Mn2+, Cu2+) present in different environments and symmetries. Organic radicals, common in modern, wood pulp paper, are absent in these antique samples made from rags. Fe3+ is the largest impurity (from 300 to 700 ppm). Mn2+ is also present but its concentration does not exceed 50ppm. Cu2+ has been detected in about one-third of the samples. Coupled with nuclear magnetic resonance data, these results describe degradation as an hydrolytic process leading to a net increase of amorphous cellulose and to a decrease of bound water. Copper and rhombic iron appear to act as efficient degradation catalysts, whereas the presence of octahedral iron is almost irrelevant.