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AbstractLong-time preservation of manuscripts depends on the stability of their support. One of the most important degradation processes of paper manuscripts containing iron gall ink is the acid hydrolysis of cellulose. The heterogeneity of the distribution of their constituent materials, together with the defined position of ink as a source of degradation agents, makes it difficult to obtain reliable and detailed information about degradation processes. The aim of this study is to contribute to the knowledge of the acid degradation process by looking at the distribution of relevant variables (pH, acidity and alkaline reserve) on real untreated iron gall ink containing manuscripts at different degradation stages. The study discusses the well-known differences between surface and cold extraction pH determination. It corroborates the relationship between pH, acidity and alkalinity and degradation stages, pointing out that acidity values for some manuscripts in apparent good condition are not far from those obtained for degraded manuscripts. The results indicate that in some partially degraded manuscripts, the coexistence of acid areas and areas with an alkaline reserve which do not participate in the neutralization process is possible. The role of water as a solvent for this equilibrium has also been evaluated.

Fourier transform infrared (FTIR) is an efficient tool to analyse deposits on iron gall inscriptions that appear on historic documents. Deposits look like white powder or whitish crystals under a microscope. Crystals show cubic or needle shapes with sizes below 20 μm. Mapping infrared spectroscopy in addition allows the selective identification of mixed deposits. Selective analysis of different inorganic oxalates is possible in four regions of the mid-infrared spectrum, thus avoiding interferences with bands of other compounds present. Calcium, potassium and iron oxalates, further calcium sulphate, calcium carbonate, basic iron sulphates and iron ammonium sulphate were identified on samples taken from selected manuscripts. The results enabled to establish a correlation of ink composition and the observed intensity of ink corrosion.

AbstractIron gall ink’s natural acidity promotes the degradation of manuscripts. This process mostly affects the areas containing ink, causing fragility of the paper carrier that limits its manipulation. The cellulosic material is modified by two chemical reactions, acidic hydrolysis and oxidation, both depending on the pH of the paper. This article explores the distribution of acidity in manuscripts and its link to iron gall ink corrosion and cellulose degradation. Subsequently, different treatment methods of deacidification, specifically designed for extremely degraded paper documents and sheets bound in volumes were tested. Documents were deacidified and at the same time mechanically supported, using an alkaline compound for deacidification that increases the pH to a range at which iron ion oxidation is decreased. Three alkaline compounds at different concentrations were evaluated: (1) calcium carbonate microparticles, (2) calcium hydroxide nanoparticles and (3) calcium propionate solution. The immediate and long-term effects after ten months of storage of these compounds on the increase of the pH of manuscripts are described in this study. All tested compounds were able to increase the pH and maintain it in the course of the observed period. Moreover, a lining with thin tissue and a mixture of 3 % gelatine dissolved in 60 % water and 40 % alcohol provides the consolidation required for manipulation of the manuscripts.