Archaeological finds

Where were the wood artefacts from the ArCo project found? How were they preserved along these years and in what conditions are they now? The answer to these questions can be found below.

With ArcGIS
Location of the archaeological finds included in the ArCo project.


In the past, several boats and ships were abandoned throughout Europe, either on purpose or due to accidents. Some of them have been discovered in the last decades in surprisingly good conditions; found underground, in the sea or in lakes. This provides good conditions to preserve waterlogged wood since these environments are deficient in dissolved oxygen and hence slow down degradation, especially when the wood is covered by sediments. Although some wooden artefacts were quite fragmented it was possible to mount the pieces together. Nevertheless, these waterlogged artefacts had to be treated in order to stabilize and preserve its wooden structure, i.e. the water that has seeped into the wood during burial had to be removed or replaced. Otherwise the wood would be in danger of biological degradation and/or dimensional changes due to constant water evaporation. The archaeological finds from Norway, Denmark and France included in the ArCo project (see map) consist of different types of wood and were subjected to various conservation treatments. Their current condition is a reflection of the burial environment and the materials used to construct and conserve the wooden artefacts.

Lyon

Abandoned: AD 158–185

Photo from ARC-Nucléart
Excavation of the Gallo-Roman wreck LSG4 at Saint-Georges, Lyon. Photo: ARC.

In the Saint-Georges district in Lyon (France), archaeological remains were found while an underground car park was built. During the excavations conducted in 2002–04, sixteen wrecks from different eras were discovered, representing ancient shipping trends and harbour activities, since this site was in times a bank of the river Saône. Among these finds was the Gallo-Roman ship LSG4, one of the best preserved wrecks selected for later display in a museum. Due to the dimensions of the boat (original length: 28 m) and the ongoing constructions, six sections (in total: 18 m) were excavated and preserved in a lake near Lyon. This flat-bottom ship, made of oak and fir tree and fastened with iron nails, was taken out of the lake after ten years in order to be treated. So far the nails have been removed and the holes treated with a disodium sebacate solution, to prevent acidification. Furthermore, the wooden artefact is undergoing a PEG/freeze-drying treatment until the end of 2016.

Samples for ArCo:

  • Untreated softwood samples, containing iron salts or mineralised
  • 20% PEG + 10% disodium sebacate treated and freeze dried oak wood sample, containing iron salts
  • Iron nail with mineral concretions
     

Nydam

Sacrificed: AD 250–475

Nydam Bog’s first excavations were carried out in 1859–63 and proceeded later on, north of Sønderborg in southern Denmark. The bog was located in Nydam and contained several boats, weapons and other equipment from the Iron Age. What once was a lake became a sacrificial bog where boats and other wooden objects from defeated armies were used as offerings to the gods; this environment provided excellent conditions to preserve the wood. Nydam’s artefacts were made of wood species such as pine, oak and ash and some of them were ornamented with gold, silver and bronze. At the time excavations were in progress, certain objects were selected to be preserved through freeze drying (using the cellosolve method) while others remained untreated. Some of them were treated more recently with polyethylene glycol (PEG) and freeze dried. Nowadays, a weakened wooden structure can be observed, possibly due to the decomposition of crucial wood components (e.g., cellulose, hemicellulose and lignin).

Samples for ArCo:

  • Unimpregnated freeze dried ash wood sample
  • PEG (2000 g/mol) treated wood sample
     

Oseberg

Buried: AD 834

Photo from Olaf Væring, Museum of Cultural History/UiO
Excavation of the Oseberg find in 1904 at Tønsberg. Photo: Museum of Cultural History, UiO/Olaf Væring.

In 1903, during farming activities in the Oslofjord region (near Tønsberg) a ship burial from the Viking Age was found. It is believed that the Lille Oseberg farm was in times used as burial ground for two women from high society. The Oseberg find consisted of an almost complete wood ship that contained ceremonial objects (e.g., wooden sledge and wagon), several animals, textiles and a variety of everyday life tools and equipment. The timber was built with oak and other wooden artefacts were made from pine, maple, birch and ash. Despite its age, it was possible to reconstruct the oak artefacts through simple application of linseed oil and creosote, after mounting the fragments together using metal joiners. The birch and maple artefacts were more deteriorated, so that the water inside the wood had to be replaced with alum before drying, to prevent shrinkage and deformation of the wood. The release of sulfuric acid from this treatment caused an acidic environment in the wood, resulting in extensive decay of major wood components. The corrosion of metal joiners may also have contributed to this degradation. Today, many of these objects have become fragile and cracks and voids have been formed.

Samples for ArCo:

  • Alum treated birch wood samples, containing areas rich and poor in alum salts
     

Skuldelev

Sank: AD 1070–1090

Five ships from the Viking Age were excavated in 1962 in the Roskilde fjord, near Skuldelev. In order to protect from intruders what at that time was the capital of Denmark, a barrier was created in a natural channel in the Roskilde fjord. Three ships filled with stones were sunk in the 1070–1090’s, followed by other two in later times. These ships were built in Denmark, Norway and Ireland mainly with pine and oak wood but ash, birch, lime and alder wood were also used. To avoid shrinkage and cracking of the artefacts after excavations, the timbers were impregnated with an aqueous PEG solution. However, this consolidation material has degraded over the years, becoming more susceptible to humidity and producing acids inside the wood.

Samples for ArCo:

  • PEG (4000 g/mol) treated and air dried oak wood samples
     

La Lomellina

Sank: AD 1516

The Lomellini’s cargo vessel was discovered in 1979 in the Villefranche sur Mer harbour, near Nice (France). It was built in Genoa and intended to transport weapons and ammunitions from France to Italy during war. It was being repaired when a heavy storm came up in the harbour, causing several ships to wreck. The excavations took place until 1991 and the archaeological artefacts made of wood like oak, pine, beech and walnut were conserved in fresh water containing fungicide before being treated. During treatment, the wooden artefacts were completely or partially impregnated with two different PEG solutions (molecular weights: 400 g/mol and 4000 g/mol); partially impregnated artefacts were freeze-dried. At the moment, depletion of cellulose, metal corrosion and mineral outbreaks can be observed; all of them are signs of weakness of the artefact.

Photo from ARC-Nucléart
Piece of the wooden structure that supported the main sail of La Lomellina. Photo: ARC.

Samples for ArCo:

  • PEG (4000 g/mol) treated softwood sample, containing iron salts
  • PEG (4000 g/mol) and 20% PEG + 10% disodium sebacate treated softwood sample, containing iron salts
     

l'Aimable Grenot

Sank: AD 1749

Two privateer vessels were found in 1995 at the Natière reef near Saint-Malo, France. This harbour was in times a strategic trade spot with a dangerous coastline; many ships sunk in these waters including l’Aimable Grenot. During the excavations in 1999–2008, some timber sections and objects covered by sediments were found to be in quite good conditions. The timber had a robust structure built with oak and beech wood and, even pieces of a large figurehead made of pine and alder were found. These pieces belonged to a tall figure representing the former navy commissioner Charles Grenot. The main structure of the ship has been protected from currents and other aggressions and been preserved in situ through a sediment coating. Some of the objects and structural elements have been sent to laboratories for treatment; the archaeological wood is undergoing a PEG/freeze-drying treatment.

Samples for ArCo:

  • PEG (4000 g/mol) treated oak wood samples, containing iron salts or mineralised
  • PEG (4000 g/mol) and 20% PEG + 10% disodium sebacate treated and freeze-dried oak wood samples, containing iron salts or mineralised
  • PEG (4000 g/mol) treated oak wood sample, containing iron salts and starting acidification

Find out more

Nydam
Nydam Society, Denmark

Oseberg
Viking Ship Museum, Norway

Skuldelev
Viking Ship Museum, Denmark

l’Aimable Grenot
La Natière, France

By Maria Laura Amberger
Published Oct. 6, 2015 3:42 PM - Last modified Sep. 12, 2018 12:32 PM