Assessment of Various Iron Extraction Treatments on Waterlogged Archaeological Oak
Author:
Pelé-Meziani Charlène1, Macchioni Nicola2ORCID, Sozzi Lorena2, Guilminot Elodie1, Lemoine Gwenaël1, Pizzo Benedetto2ORCID, Mevellec Jean Yves3ORCID, Pecoraro Elisa2ORCID, Monachon Mathilde4
Affiliation:
1. Laboratoire de Conservation-Restauration Arc’Antique, 44300 Nantes, France 2. CNR-IBE, National Research Council of Italy, Institute of Bioeconomy, 50019 Florence, Italy 3. CNRS, Institut des Matériaux de Nantes Jean Rouxel, Nantes Université, IMN, F-44000 Nantes, France 4. Laboratory of Technologies for Heritage Materials, Institute of Chemistry, University of Neuchâtel, 2000 Neuchâtel, Switzerland
Abstract
Treatments of organic objects to extract ferrous compounds from waterlogged archaeological wood are well documented. For several years, numerous laboratories have been seeking to determine suitable conservation treatments for such organic objects. For chemical treatments, complexing agents such as EDTA and DTPA, along with acids such as citric and oxalic acids, were selected. In addition, oxidants and reducing agents were tested as pre-treatments to improve extraction rates. In fact, chemicals produce a selective reaction on ferrous compounds, which may improve or be inhibited by complexation or dissolution reactions. Their action depends on the type of compound to be extracted and those present inside the wood. The objective of this study was to make a comparative assessment of the various chemical conservation treatments identified and complement the evaluation of their extraction efficiency with a study of their impact on organic matter by adding criteria such as their visual aspect (using a spectrocolorimeter) and physicochemical actions by means of infrared spectroscopy and micromorphological observations. The effectiveness of EDTA was confirmed, as was that of citric acid, despite some questions arising concerning the presence of wood fibers in the treatment solution, even after rinsing. On the other hand, the extraction rate of oxalic acid, which has a very acidic pH, was unsurprisingly lower, but its visual and anatomical results raised the possibility of using it over a short period of time in view of the effectiveness observed on the wood surface. Pre-treatments improved extraction rates, except in the case of EDTA, which independently had a high extraction rate. It was observed that pre-treatments did not appear to cause any significant chemical degradation of the organic matter. This study provides a tool to assist conservators in selecting a chemical treatment that is in line with the state of decay of the wood, the characteristics of the ferrous compounds to be extracted, and the conservation objectives.
Funder
Direction Régionale des Affaires Culturelles des pays de la Loire
Reference47 articles.
1. Hoffmann, P., Spriggs, J.A., Straetkvern, K., and Gregory, D. (2004, January 4). Analyses of Sulfur and Iron in Marine Archaeological Wood. Proceedings of the 9th ICOM Conservation Group on Wet Organic Archaeological Naterials, Copenhagen, Denmark. 2. Extraction of iron compounds from wood from the Vasa;Almkvist;Holzforschung,2006 3. Sulfur and iron analysis of marine archaeological wood in shipwrecks from the Baltic Sea and Scandinavian waters;Fors;J. Archaeol. Sci.,2012 4. Characterization of degradation and iron deposit of the wood of Nanhai I shipwreck;Zhang;Herit. Sci.,2022 5. Pelé, C., Moulhérat, C., Lemoine, G., Labroche, S., Guilminot, E., and Baron, G. (2013, January 13–17). Extraction of iron compounds from marine organic objects. Proceedings of the 12th ICOM Wet Organic Archaeological Materials Conference (WOAM), Istanbul, Turkey.
|
|