Marine archaeological wood often suffers from acidification processes that lead to the degradation of the fibres, threatening the integrity of archaeological artefacts. Iron ions originating from corroded fixtures, nails, or other objects diffuse into the structure of waterlogged wooden artefacts over time, playing a key role in their degradation. The presence of iron ions and oxidised sulfur species in marine archaeological wood has been linked to the formation of sulfur-based acids and to the oxidative degradation of cellulose and hemicellulose.[1,2] These processes have deleterious effects on the structural integrity of wooden artefacts and pose a major challenge in the long-term conservation of marine archaeological wood.[3] This thesis describes the design, synthesis, characterisation, and preliminary tests of a series of conservation treatments aiming for the sequestration and complete removal of harmful iron species present in waterlogged wood, thus preventing the formation of acidic species. These treatments consist of magnetic nanocomposites which contain iron chelating agents and are encapsulated in a polyethylene glycol-based, thermoresponsive polymer for a safe and controlled application. The iron sequestering capability of the nanocomposites range between 39 and 80 % when tested in aqueous solution. Far IR spectroscopy studies on preliminary treatments on artificial archaeological oak and Mary Rose wood samples indicate that iron ions are successfully removed from the wood by the nanocomposite-laden polymer.
These conservation treatments are capable of removing harmful iron ions from marine archaeological wood, and a number of parameters in their preparation can be adjusted to meet the requirements of different artefacts to be treated. The combined magnetic and thermoresponsive properties of these materials allow for a safe and controlled application of the treatments and opens new possibilities in the design of novel non-invasive conservation strategies. While previous conservation treatments aimed to remove the iron ions or to neutralise the acidic species present in the wood, the approach presented here manages to physically remove iron ions from not only the surface, but also from the wood structure. Due to the high tunability of the systems developed, these can be applied for the conservation of many other materials such as stone, paintings, fabric, or leather.
[1] G. Almkvist and I. Persson, Holzforschung, 2008, 62, 694–703.
[2] K. M. Wetherall, R. M. Moss, A. M. Jones, A. D. Smith, T. Skinner, D. M. Pickup, S. W. Goatham, A. V. Chadwick and R. J. Newport, J. Archaeol. Sci., 2008, 35, 1317–1328.
[3] M. Sandström, F. Jalilehvand, I. Persson, U. Gelius, P. Frank and I. Hall-Roth, Nature, 2002, 415, 893–897.
