Conservation Science

The state of preservation of iron artefacts from Nydam showed a very vary-
ing picture, with some objects being completely converted into corrosion
products, while the original surface of others was still visible. During the
excavation, it was noted on some occasions that well-preserved and heavily
deteriorated objects were lying just a few centimetres from each other. In order
to evaluate this further, a group of artefacts (spear and lance heads) were
selected for a closer study of their state of preservation. The spear and lance
heads were X-rayed, and the corrosion depth was measured at 20–30 positions
on each artefact and averaged. The measured corrosion depths were correlated
to the exact find position using a Geographical Information System (Figure 7).

324 Chapter 12

N

5 m

a)

b)

> 1.75

1.5 to 1.75

1.25 to 1.5

1 to 1.25

0.75 to 1

0.5 to 0.75

0.25 to 0.5

0 to 0.25

Gyttja

Peat

1 m

N

Iron age

shore line

Corrosion depth (mm)

0.1 m

2.60

2.50

2.40

2.30

Figure 7Corrosion depth of a group of lance and spear heads excavated in 1994. (a) Plan view,
where solid lines indicate modern excavations and dashed lines show excavations
during the 19th century. (b) Vertical profile (seen from SE) where dashed line indicates
interface between peat and gyttja. Solid line at each point represent a projection of the
lance or spear head to the vertical view plane, so long steep lines indicate artefacts
deposited in a steep angle. Numbers to the left are metres above sea level