condition of finds from excavations in the 1990s, are under most threat of
deterioration if left in situ.
4.2 Deterioration and Protection of Wooden Artefacts
From the amount of wooden finds still in Nydam, the environmental conditions
can be considered conducive to the preservation of wood. However, archaeo-
logists working at Nydam were concerned that the finds excavated during the
1990s were in a worse state of preservation than those excavated in the 19th cen-
tury. This concern is based on three observations. First, the last 10–15 years has
seen the growth of “horsetails” (Equisetum) over Nydam. Although they seem
quite small and innocuous on the surface, their root system can grow down one
to two metres. This not only brings oxygen down to the find layer but, more
drastically, the roots actually penetrate the artefacts.
Second, when the artefacts are viewed by eye, there is a distinct difference
between many of the artefacts in the different find layers. Many in the upper find
layers have a roughened, gnarled surface appearance whereas those in the lower
find layers often retain many surface details (Figure 5). Third, density meas-
urements taken on the planking from the boats excavated in 1864 showed that
the average density was 460 kg m^3 , whereas smaller artefacts excavated more
recently show an average density of 100 kg m^3. Monitoring alone could not
substantiate these observations. Therefore, a series of artefacts, representative
of those in the different find layers, were analysed to assess their state of
preservation through determination of their density and cell wall components
(cellulose and lignin). DNA was also extracted to try to identify the micro-
organisms, which had caused deterioration. Macroscopic and microscopic analy-
sis of artefacts enabled background information on the post-depositional
processes of deterioration and the present state of preservation to be investi-
gated. Furthermore, experiments looking at the deterioration of wood by basid-
iomycete fungi and the tendency for artefacts to collapse, showed what could
happen should the water level in Nydam fall below that of the find layers.
Macroscopic analysis of artefacts from the upper find layers in Nydam
showed that those artefacts, which, from their surface details, appeared to be
in a poorer state of preservation, were actually degraded prior to their incorp-
oration in the meadow. Through the analysis of the surface of the artefacts it
was possible to elucidate that the most likely cause of the deterioration was
through the activity of the wood-boring beetle Nacerda melanura, which is
often found to cause deterioration of wood that lies exposed in, and around,
wet environments. This would suggest that the artefacts displaying such sur-
face details had lain exposed, perhaps floating on the surface of the lake,
prior to being incorporated in the bog. This observation was also supported
by microscopic analysis of their structure. They also showed a dark ring
320 Chapter 12