Standing on the shoulders of our predecessors - a base and a viewpoint. Fifty years of working with conservation of waterlogged archaeological shipwrecks in Denmark.

Although nearly 50 years apart, the Roskilde ships
would follow nearly the same steps during their conservation as the Skuldelev ships. These steps include:
assessment of the state of preservation of the wood,
selected impregnation and drying methods, recommended exhibition climate, mounting for exhibition,
maintenance and evaluation of long term stability. The
different methods used for conservation reflect the extensive technical and economic resources required for
the conservation of shipwrecks. When resources are
limited, large archaeological finds often lead to development of new, less resource demanding methods
when scientific and technical progresses made over a
period of time evolve into new and better conservation
methods.
The Skuldelev ships were excavated between 1957
and 1962 and conserved in the period from 1962 to
1975. When the conservation of the wrecks started,
the most used methods were still alum and creosote/
petroleum treatments. As these methods were quite
inadequate, the Skuldelev ships were the first wooden
archaeological finds to be conserved with Polyethylene glycol (PEG) in Denmark and thereby opening a
whole new era in conservation at the National Museum. New conservation methods, such as 100% PEG
impregnation and freeze-drying from tertiary butanol,
were introduced.
Several years later a new large archaeological find, the
Roskilde ships, was discovered during excavation of
a new museum harbour at the Viking Ship Museum
in Roskilde. The excavation took place from 1996
to 1997 and when the conservation started in 1998,
PEG was still the most frequently used impregnation
agent for waterlogged wood. However, its application has changed over the years due to the progress in
the conservation skills and technical developments.
For example, wood has been impregnated with 40%
aqueous PEG solutions and freeze-dried in moulds to
obtain the correct shape in order to minimize handling
and destruction of the surface of the wood.