Page 183 - Manual for Activities directed at the Underwater Cultural Heritage

meters. These parameters are related to the nature of water, to living organisms (microscopic and macroscopic), and to the type of substrate and silt/ sand upon which the site is located respectively. After a few years, equilibrium is achieved between the surrounding water and the artefacts leading to a relative stabilization of degradation processes. Burial in underwater environments may thus have several effects: structures are weakened though they may still appear solid while on the seabed, and layers incorporating sediments and concretions (thick surface overgrowth) may develop.
Recovery and its impact on artefacts
Raising objects from underwater inevitably results in them drying, which in turn accelerates degra- dation. This is due to the presence of soluble salts dissolved in the surrounding solutions on the seabed. In the new environment they dissolve or crystallize de-pending on relative humidity. Damages to the artefacts are likely to occur due to these potentially
 © U. Guérin / UNESCO.
In 2000 and 2002, two wooden wrecks were found
in the harbour of Antwerp during the construction of the Deurganckdock. Specialists soon identified these wrecks as medieval cogs, the typical large merchantmen from the time
in which the Flemish cities had their economic height.The first cog, is one of the most complete of all medieval shipwrecks ever found in Europe. At the time
of the finding there was very limited time to do research on site.Therefore every plank and timber had to be disassembled and was put in a container with water to prevent it from rotting. In total 455 timbers of both cogs were placed in 33 containers.
The Flemish Heritage Institute (VIOE) started its multidisciplinary research in the summer of
2010 at the Flanders Hydraulics Research (Waterbouwkundig Laboratorium) in Borgerhout, Antwerp.
182 destructive physical pressures applied onto very
As part of “preventive conservation” it is cru- cial to ensure that from the minute it leaves the water, any object is kept in an environment identical or close to that in which it was found.
Conservation and site management