Different methods for soluble salt removal tested on late-Roman cooking ware from a submarine excavation at the island of Pantelleria (Sicily, Italy)

Abstract

tThis paper deals with the comparative evaluation of different procedures of salt extraction designed forarchaeological ceramics from submarine burial environments. The experimental work was carried outon a particular type of late-Roman cooking ware finds (Pantellerian ware) found in a shipwreck near theshoreline of the Island of Pantelleria (Sicily). The studied ceramic test-pieces were first recognised in termsof bulk characteristics (mineralogy, petrography and chemistry). SEM-EDS observation allowed verifica-tion of the presence of various secondary minerals at the surface and in the pore spaces formed after theprolonged permanence in seawater under oxidising or reducing conditions. Pore-size distribution wasalso determined in the same fragments that had been subjected to the salt extraction routines. Threesalt extraction methods were tested: two methods based on diffusion processes (water immersion understationary conditions and under mechanical stirring conditions) and one method based on both diffusiveand advective processes (multiple packages of sepiolite). The obtained experimental data allowed us toidentify strengths and weaknesses of the tested procedures with practical spin-off for archaeologists andrestorers (efficiency, kinetics, compatibility with the ceramic substrate, costs and simplicity of use). Saltextraction under mechanical stirring was the most effective method and, for this reason, is suitable forlaboratory fieldwork during or immediately after submarine archaeological excavations. Similar advan-tages are also intended for the preliminary treatments of the most precious findings prior to museumstorage.