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

摘要

ABSTRACT: Many western manuscripts were written using iron gall inks. These inks can damage the paper via two majornmechanisms: (a) acid hydrolysis, enhanced by humidity, and (b) oxidative depolymerization provoked by the presence of oxygen andnfree iron(II) ions. The degradation of unsized Whatman paper impregnated with different combinations of iron sulfate, gallic acid,nand gum arabic was studied at room temperature in order to assess the relative importance of each mechanism. The samples werenstored in various environments including a dry and/or an oxygen-free atmosphere. The cellulose depolymerization wasmonitored bynviscometry and related to changes in the oxidation state of iron, determined by X-ray absorption near-edge spectrometry. The resultsnindicate that residual amounts of oxygen (less than 0.1%) promote cellulose depolymerization, whereas the level of relative humiditynhas no impact. The cellulose depolymerization also appears closely correlated to oxidative mechanisms. Regarding the oxidation ofniron, it only occurs in the simultaneous presence of oxygen andmoisture, suggesting the occurrence of rustlike oxidativemechanisms.nFinally, the presence of gallic acid has a strong influence, which is only partially explained by its capacity to reduce iron(III) to iron(II).