Non-destructive Investigation of Salt Efflorescence on Roman Tomb After Relocation in Ancient Corinth, Greece

Abstract

The relocation of excavated monuments raises serious conservation and ethical problems. Although in situ preservation is usually preferred, in some cases, the relocation of finds is inevitable for various reasons. Tomb 313, a roman monument found near Corinth in 2012 during the construction of a major motorway, has been relocated to a new position in the premises of the archaeological site of Ancient Corinth since it was impossible to be preserved in the excavation site. The tomb was decorated with wall paintings, depicting garlands, fruits and three figures, two men and a woman, found in excellent state of preservation. Although the tomb has been externally insulated during the excavation and transport, its state of preservation decreased radically after the relocation. The microclimate of the tomb retained high relative humidity, but gradually the wall paintings were cover by salt efflorescence. In order to estimate the risk and the actions needed to prevent damage, it was necessary to execute rapidly diagnostic techniques. For this reason, mapping and evaluation, in situ non-destructive testing was performed on the monument by means of IR thermography along with examination of soluble salts samples by means of scanning electron microscopy and X-ray diffraction. Results obtained by the IRT monitoring suggest the existence of high moisture accumulation on the salt-infected side of the tomb. The IRT examination of the wall paintings showed that moisture penetration is probably transporting salts from the immediate environment. Salt analysis showed that the origin of the salts is probably the concrete slabs that have been used for the reinforcement of the monument during transport. Due to the high relative humidity environment, gypsum salts were transported to the surface of the wall paintings and crystallized as efflorescence without the generation of damage. The results also suggested the future actions for the preservation of the wall paintings and the exhibition of the monument. IRT monitoring is a fast and reliable diagnostic technique that can provide a solid basis for salt weathering investigations.