The three stelae project
After two years of work, the conservation and restoration of the three stelae on the Bartholomew cemetery in Göttingen/Germany could be completed.
The three classical steles where erected in the first half of the 19th century and consist of local red sandstone. They have been exposed in a comparable situation and originated at about the same time. However even the three objects are made of very similar stone they show very different weathering forms. The first one show sanding the second one alveolar like weathering forms and the third one intense flaking. Most weathering phenomena can be observed at the eastern site of the stelae where the inscriptions are placed.
The steles were desalinated, consolidated and finally restored.
Desalination was carried out by a drip injection method in combination with the poultice method. The drip injection system, combined with a poultice was installed at the undamaged back of each stelae and isolated with a thin plastic film. Like this the poultice at the back side stood always wet and could not dry out. By this a permanent water flow was produced towards the opposite site of the drip system. At the opposite eastern side also a poultice was applied that could be dry out and therefore could collect the salts transported by permanent water flow.
Previously, the electrical conductivity and the electric capacity of the stone surfaces and surface near zone were detected in the grid. After drying the content of soluble goods of the poultice was tested.
Ultrasonic velocity measurements as well as surface hardness measurements were performed before and after consolidation with silica acid ester.
Finally, the stelae were restored using a self-produced hot lime mortar.
The results of the campaign will be present at the 14th International Congress on the Deterioration and Conservation of Stone that will take place from September 7 till 12 2020 in Goettingen/Germany. During the congress also an excursion is planned to visit our local restoration works.