An Experimental Gel-Based Treatment of Iron Gall Ink Corrosion Halos: Sodium Metabisulfite and Diethylene Triamine Pentaacetic Acid Solution in Agarose Gel

Abstract

A research project was carried out at Queen’s University to determine the effectiveness of an agarose gel-based treatment of iron gall ink corrosion halos using reducing agent sodium metabisulfite and chelating agent diethylene triamine pentaacetic acid. The ink fabricated for this experiment contained the metal ions of iron, copper, and zinc to increase the amount of visible corrosion, as well as replicate historic inks that have metals other than iron in them. The experimental treatment accounts for the chelation of the copper and zinc ions from the paper substrate along with iron, which cannot currently be done using the widely accepted calcium phytate treatment, as phytate is iron selective. The effectiveness of this experimental treatment was primarily determined using qualitative methods of analysis. Photographic documentation, ultraviolet fluorescence, and optical microscopy showed visual effects of the treatment from color change in the ink, to a reduction in corrosion-induced fluorescence, and ink bleeds where the cyclododecane fixative failed. Scanning election microscopy-energy dispersive X-ray spectroscopy and electron probe microanalysis were the techniques that made clear the distribution of elements in the ink and from the treatment on the paper samples. However, the concentrations of metals in the substrate were too low to detect evidence of corrosion halos via these analytical methods. Color spectrophotometry and pH measurements of the sample swatches yielded results that support observations made with the aforementioned techniques and determined the treatment safe for the paper substrate, respectively. Unfortunately, inductively coupled plasma atomic emission spectroscopy, the main technique that could have confirmed the success of the treatment, did not yield results because of unknown error. Though no definite conclusions could be drawn on the effectiveness of the treatment, suggestions for future research and potential treatment procedures can be considered based on the results from the qualitative analyses.