Phytate treatment of metallo-gallate inks: Investigation of its effectiveness on model and historic paper samples

Abstract

The aim of this study was to confirm the stabilizing effect of phytate treatment on iron gall ink degraded cellulose and papers on a molecular level. The impact of iron gall ink degradation on the cellulose molecule and its stabilization can be studied with very low sample amounts by fluorescence labelling of carbonyl groups in combination with GPC-MALLS to determine the weight averaged molecular weight. The aqueous phytate treatment, a complexation of transition metal ions using calcium phytate, and a deacidification treatment using calcium hydrogen carbonate, was applied on Whatman filter paper, and on modern and historic rag paper. Model iron gall inks were plotted on the test papers, while all historic rag papers contained iron gall ink. To gain insight into the long term stability, an ageing step was performed after the phytate treatment, and treated samples were compared to untreated ones. The positive impact of this treatment was verified for the first time on a molecular level, showing that molecular weight and carbonyl group content were significantly stabilized. The stabilization was proven on the inked areas and on pure cellulose. It was also confirmed the even copper containing inks will benefit from the treatment.