Treatment of Waterlogged Archaeological Wood Using Chitosan- And Modified Chitosan Solutions. Part 1: Chemical Compatibility and Microstructure

Due to problems with most of the existing conservation treatments, new materials for the stabilization of waterlogged archaeological wood are highly desirable. The ideal consolidant should be environmentally friendly and safe to work with for conservators, while strengthening the objects without ruining the visual impression of the wood or filling it in ways that prevent re-treatment in the future. This paper tests chitosan since it is a multifunctional material that not only offers support but also hinders catalytic activity by potentially chelating reactive metal ions. Three solutions of 2% chitosan in 0.1 M acetic acid were chosen as a consolidant for samples from a 1150-year-old piece of waterlogged Viking Age wood from Slagen prestegård. The penetration of chitosan was determined by freeze-drying the samples and analyzing them using high-performance liquid chromatography (HPLC). It was found that chitosan solution penetrated at least 1 cm into the wood along the grain over the span of 2 weeks. Depolymerizing the chitosan only improved uptake slightly. The chitosan left an open structure in the waterlogged archaeological wood. It offered some strength to severely degraded waterlogged wood, but further tests are needed to evaluate stability, shrinkage, and fixation.