X-ray spectrometry aids understanding of how iron gall ink degrades paper

A French-Belgian joint group led by Dr. V. Rouchon (Centre de Recherche sur la Conservation des Collections, MNHN-MCC-CNRS, France) and Professor K. Janssens (Universiteit Antwerpen, Belgium) recently published an interesting paper on the application of X-ray spectrometry to cultural heritage. For many years, in Europe, iron gall inks have been used for writing manuscripts, and they could damage the paper via two major ways: (i) acid hydrolysis, enhanced by humidity, and (ii) oxidative depolymerization provoked by the presence of oxygen and free Fe(II) ions. The present research aimed to give some quantitative evidence for each contribution by studying depolymerization of cellulose under various environmental conditions, with viscometry and related changes in the oxidation state of iron determined by X-ray absorption near-edge spectrometry. It was found that residual amounts of oxygen (less than 0.1%) promote cellulose depolymerization, whereas the level of relative humidity has no impact. For more information, see the paper, "Room-Temperature Study of Iron Gall Ink Impregnated Paper Degradation under Various Oxygen and Humidity Conditions: Time-Dependent Monitoring by Viscosity and X-ray Absorption Near-Edge Spectrometry Measurements", V. Rouchon et al., Anal. Chem., 83, 2589 (2011).