In 2006 a Bronze Age log boat was recovered from the banks of the Tay at Carpow. Perth & Kinross Historic Trust formed a partnership with National Museums Scotland for the conservation of this remarkably preserved 9m+ long boat. Without appropriate treatment the waterlogged timber would shrink and deform. Treatment required understanding the material science of waterlogged wood, knowing the degree of degradation and water content of the oak, and having access to large scale specialist facilities and expertise.
The Carpow longboat during excavation ©RCAHMS
Dr Theo Skinner, who was responsible for the conservation, reviewed possible treatment methods before selecting impregnation by polyethylene glycol (PEG) followed by freeze drying. Scanning Electron Microscopy (SEM) was used to identify surface accretions. Sulphur was found as a potential problem, and samples were taken for further analysis by X-ray spectroscopy at the Swiss synchrotron facility.
In collaboration with The Mary Rose Trust a potential new method to prevent the future build up of damaging sulphuric acid using calcium phytate was devised. The depth profile of water content in the timber was measured and used to specify the necessary PEG treatment and impregnation times, a programme which ran for approximately 18 months. Each section of the log boat was then treated in the NMS large object freeze drier (developed as a national facility for conservation of marine and wetland material), monitoring progress by measurement of water loss. Conservation work will run to the end of 2011, the integration of scientific analysis and measurement continuing hand-in-hand with practical treatment throughout.
Return to Section 3.9 Conservation science