History of Conservation: Early Treatments for Waterlogged Wood

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CCI Newsletter, No. 34, December 2004

History of Conservation: Early Treatments for Waterlogged Wood

by David Grattan, Manager, Conservation Processes and Materials Research

The treatment of waterlogged wood is a central issue in the conservation of shipwrecks or archaeological wet-sites. Waterlogged wood (i.e. wood that is saturated with water) retains its form but loses substance and strength through bacterial degradation with increasing age. Such wood can distort or disintegrate entirely on drying. Although Canada is rich in archaeological wet-sites and also in historic shipwrecks, and Canadian institutions have pioneered many techniques to preserve the finds from such sites, it is in Europe where the early history of treatment is found.

The conservation of waterlogged wood seems to have begun independently in two locations: Denmark and Switzerland. In Denmark, ancient burials found preserved in the peat bog had waterlogged wooden artifacts associated with them. By the mid 19th century, these were routinely treated by soaking them in a boiling solution of alum (potassium aluminum sulphate) in water. This mixture entered the wood as a liquid and replaced the water. On cooling, it congealed and created a solid mass that physically prevented the wood from shrinking when drying. This process was first described sometime in 1859 by Jorgensen "a trusted servant" of the King of Denmark, and was used extensively until the mid 20th century. It was another Dane — namely Brorson Christensen — who in the 1960s developed a much better method of treating waterlogged wood using a water-soluble plastic (namely, polyethylene glycol) and who also described this early history of treatment. His book Conservation of Waterlogged Wood in the National Museum of Denmark,¹ is probably the most erudite writing on the topic. It is a wonderful resource for those interested in the treatment of waterlogged wood.

1. Christensen, B.B. The Conservation of Waterlogged Wood in the National Museum of Denmark. Studies in Museum Technology, No. 1. Copenhagen: National Museum of Denmark, 1970.