A Preliminary Investigation Into the Use of Diethylenetriaminepentaacetic Acid (DTPA), and Ethylenediaminetetraacetic Acid (EDTA) to Treat Foxing of Paper Objects.

Prestowitz, Brook, Theodorakopoulos, Charis and Colbourne, Jane (2016) A Preliminary Investigation Into the Use of Diethylenetriaminepentaacetic Acid (DTPA), and Ethylenediaminetetraacetic Acid (EDTA) to Treat Foxing of Paper Objects. In: The 44th Annual Meeting of the American Institute for Conservation of Historic and Artistic Works (AIC) and 42nd Annual Conference Canadian Association for Conservation, 13 - 17 May 2016, Montreal.

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Abstract

Foxing is a general term used to describe a type of localized, brown staining that may be caused by a range of deterioration agents active in paper objects. This research focuses on foxing caused by iron ions, a powerful catalyst for oxidative cellulose degradation that is highly destructive to paper objects. Iron-induced foxing may become a serious issue during a disaster situation when increased moisture levels are encountered. Such environmental conditions may accelerate oxidation reactions within paper objects, resulting in a decrease in the structural integrity of cellulose and increased staining of an object. The severity of iron catalyzed oxidation of cellulose and the ensuing aesthetic disruption are aspects of deterioration that should be addressed with conservation treatment.
Chelating agents have been used to treat cellulose degradation caused by iron ions. In this work, a preliminary assessment of the effectiveness and practicality of chelating agents for interventive treatment of works of art on paper was conducted. Past uses of chelating agents in paper conservation were reviewed. Synthesized iron foxed samples were tested with diethylenetriaminepentaacetic acid (DTPA), ethylenediaminetetraacetic acid (EDTA), and each chelate in combination with sodium dithionite reducing agent.
The samples were analyzed under visible light ultraviolet fluorescence (280-440 nm), and optical microscopy using a Leica s6D microscope and an Olympus DP70 digital microscope with an Olympus U-RFL-T burner. A Spectro X-Lab 2000 x-ray fluorescence was used to measure iron ion levels before treatment, after treatment with chelators and sodium dithionite, and after washing in deionized water. Selected samples were further examined after testing was completed using an FEI Quanta 200 scanning electron microscope (SEM) with an Oxford Instruments INCA X-sight LN2 energy dispersive x-ray spectroscopy (EDS) and Si(Li) X-ray detector, 10mm ATW2 with a special energy resolution of 5.9 keV:133eV to investigate the physical properties of the paper fibers and iron residues after treatment. Sample brightness was measured before and after treatment using a CM-2600d spectrophotometer by Konica Minolta.
After lengthy and invasive treatment procedures, DTPA and EDTA successfully reduced levels of iron ions and visible staining in the paper samples. Foxing staining was decreased when treated with the chelates in combination with sodium dithionite. EDTA showed better results for reduction of iron ions and foxing than DTPA. An increase of paper brightness was noted after treatment; and ultraviolet fluorescence revealed signs of chemical changes in the samples after treatment including formation of tidelines and fluorescence of samples treated with EDTA. SEM/EDS and optical microscopy revealed physical changes in the paper supports after treatment related to the treatment methods tested. This study provides additional insight into the risks and benefits of some chelating agent treatments used in paper conservation.

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