Supercritical drying: a new method for conserving waterlogged archaeological materials

Supercritical drying is one physical option for drying delicate materials, including those of archaeological origin. The technique is applicable to conserving waterlogged wood in all stages of decomposition, cork and bone, and to composite materials including wood, metals and other materials. No consolidants are required when using the technique. This paper describes the theory behind the technique, and how to apply it to archaeological finds. The results obtained by the technique compare favourably to those obtained by freezedrying. Preliminary studies on the environmental stability of wood conserved by this technique are reported. As part of the supercritical drying technique involves the use of organic solvents, results from analysis of the extractives from wood are also reported.