Skinner, Theodore Patrick William Cumming; (2001) Dimensional stabilisation of waterlogged archaeological wood: An investigation of the water content of the cell wall of waterlogged archaeological wood and its replacement with water-soluble compounds. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

The water content of the wood cell wall has been investigated, for modern and waterlogged archaeological wood samples, by differential scanning calorimetry (DSC) and inverse chromatography (IC). DSC was used to measure the amount of water in the wood that did not freeze on cooling to -40° C, in samples dried to different water contents. The unfrozen water was found by plotting the heat of melting of ice in the sample against the fractional water content. For modem woods, the unfrozen water contents (UFW) were in the range 0.28 to 0.34 g water / g wood. For the archaeological woods, the UFW ranged from 0.534 up to 1.2 g water / g wood. IC was performed with chromatographic columns made of powdered wood, using ethylene glycol, diethylene glycol, sugars and narrow molecular weight distribution dextran standards as probe molecules to determine the water content of the wood cell wall. For the modem woods examined, these gave results similar to those of DSC in that no variation with wood density was found, but the results are higher. Packing columns with waterlogged archaeological wood proved to be very difficult, and no definitive results for the water content of the cell wall were obtained. The wood columns were also used to study the penetration, size exclusion and adsorption of polyethylene glycols (PEGs) and salts with the cell wall. PEGs showed a variety of elution behaviours, from size exclusion to adsorption. In balsa wood, and in all the archaeological woods studied, PEGs were adsorbed. It is suggested that this was adsorption onto the lignin. Salts were excluded from the wood pores to a degree dependent on their concentration and position in the lyotropic series. The implications for the conservation of waterlogged archaeological wood are discussed.

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