The effect of the drying method on the cell wall structure and sorption properties of waterlogged archaeological wood

Drying is a process affecting various wood properties, including its structure, moisture behaviour and mechanical properties. Since waterlogged wooden artefacts usually constitute priceless objects of cultural heritage, understanding the effect of drying on the complex interactions between the wood ultrastructure and the resulting properties is necessary to ensure their proper conservation. Hence, this was the aim of the present study, with a particular emphasis on the influence of drying conditions on the relations between the cell wall structure, dimensional stability and hygroscopicity of degraded archaeological wood. The choice of the particular drying methods was dictated by their final effect on wood appearance (dimensions). The results obtained clearly show that depending on the drying method applied, the resulting material differs significantly in structure, dimensions and sorption properties, despite the same degree of wood degradation. Air- and oven-drying resulted in the highest wood shrinkage, lower porosity, and a decreased number of free hydroxyls in the wood cell wall. The best wood dimensional stabilisation and the highest porosity were ensured by freeze- and supercritical drying. No correlations were found between wood structure and moisture behaviour. The outcome of the research may be useful for conservators who plan to provide the artefacts with proper storage conditions and effective conservation/reconservation.