Once objects are abandoned or lost, they often undergo deterioration as a result of exposure to climatic conditions, the type of soil they are buried in and conditions such as the rate at which they are buried, the proximity of other materials, compacting of the soil and leaching. For certain objects this deterioration is rapid and inevitably leads to their disappearance, while for others such change may gradually slow down and even stop. At this point, it is said that the object is in equilibrium with its environment.
The excavation of a site destroys this balance and the object to starts to deteriorate again, since it must once more adapt to new environmental conditions. This deterioration can be kept in check through the application of appropriate conservation measures, which sometimes consist simply of keeping dry things dry and wet things wet. Certain of these measures can be easily carried out by an archaeological team, meaning that the presence of a conservator in the field is not always essential. However, a conservator is called for when a fragile object must be consolidated before it can be removed or when perishable or unstable elements have to be preserved in situ.
Figure 3: A conservator at work at the Cartier-Roberval archaeological site. Synthetic resins are used to consolidate a piece of wood so that it can be removed. Photo: Blandine Daux, Centre de conservation du Québec.
If the presence of a conservator is optional for terrestrial sites, the situation is quite different for marine or underwater sites. In these contexts, an excavation without on-site conservation is the equivalent of vandalism, since all the materials found must receive conservation treatment that may sometimes be spread out over several years. For underwater archaeology, it is generally accepted that a month of intensive excavation means a year of conservation treatment in a laboratory. This estimation should be considered as a bare minimum, with certain cases calling for two or even three years of treatment.
Materials discovered on an underwater site require conservation treatment from the moment they are recovered; it is thus essential for a conservator to be involved in the archaeological project. Since organic materials like leather and wood owe their preservation to the fact that they are in water, being removed from this environment can result in them undergoing irreversible structural changes. Such changes compromise the objects’ integrity and interest from a research perspective, as well as their potential usefulness for presentation purposes. The conservation of materials from marine sites is complicated by the presence of salts, which must be extracted through long-term treatments.
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Figure 4-A: View of a marine concretion found on the wreck of the Elizabeth and Mary. An initial visual examination reveals nothing special about this lump. In fact, however, a fragile object is imprisoned in a concrete-hard matrix. Collections of the Laboratoire et Réserve d'archéologie du Québec/MCC. Photo: Jean Blanchet, Centre de conservation du Québec. |
Figure 4-B: A radiographic examination shows the image of a circular object superimposed on that of a large nail. X-ray by Michel Élie, Centre de conservation du Québec. |
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Figure 4-C: Following an initial removal of material from the concretion, the circular object appears to be a silver brooch. Photo: Jean Blanchet, Centre de conservation du Québec. |
Figure 4-D: A view of the brooch after treatment. Photo: Jean Blanchet, Centre de conservation du Québec. |
Conditions in marine sites are sometimes conducive to the formation of concretions that become as hard as concrete, concealing an amalgam of diverse objects and materials. Day after day, a conservator patiently carries out a delicate excavation in the laboratory to extricate objects, often undetectable at first sight, from the shapeless mass. In these cases, conservators frequently turn to radiography and, sometimes, tomography to obtain a better idea of the structure of the objects imprisoned inside. When this delicate excavation is done by conservators, it means that a certain amount of archaeological work is delegated to them, since archaeologists are not equipped to carry out this type of excavation nor to preserve the objects freed from the concretion.
Sometimes archaeological excavation leads to the discovery of domestic structures and architectural remains that need to be preserved for their heritage value. Given Québec’s climate and its characteristic freeze-thaw cycles, preserving such remains in situ is normally impossible without resorting to complex measures and specially built shelters. Often the best alternative for long-term preservation is reburying the remains.
Figure 5: The delicate excavation of a marine concretion; specialized equipment enables the safe excavation of the concretions. Photo: Michel Élie, Centre de conservation du Québec.
André Bergeron, Blandine Daux, Jean Dendy, Ariane Lalande, Kateri Morin et France Rémillard, conservators, atelier archéologie et ethnologie, Centre de conservation du Québec.
For more information on the work of the conservator, view the video:
André Bergeron : Restaurateur spécialisé en archéologie www.archeoquebec.com/fr/file/798