Salt weathering in desalinated and non-desalinated ceramic amphorae from underwater marine environments

This article reports on a study of Iberian, Italic and Tarraconensian amphora sherds found in different underwater marine environments. Non-desalinated fragments were compared to fragments desalinated using the procedure normally applied to underwater archaeological objects to study the efficacy of the method and determine both the state of conservation of the materials and the decay caused by salt weathering. To that end, destructive (X-ray diffraction, ion chromatography, scanning electron microscopy coupled to energy dispersive X-ray spectroscopy, mercury intrusion porosimetry) and non-destructive (computerized X-ray tomography) tests were conducted on the samples. The conclusion drawn was that the long-term salt content is closely related to firing temperature and that non-desalinated samples or samples in which desalination was not wholly effective exhibit a variety of signs of degradation that can be detected with computed tomography. CT proved to be a powerful technique for visualising and locating salts in the interior of porous materials. Keywords: Underwater ceramics, amphorae, desalination, salt weathering, durability