A preliminary investigation of compounds extracted when soaking low-fire ceramics

Teresa Myers

Abstract

Low-fire ceramics undergoing or in danger of damage from salts are often submerged in water for several days to weeks as a method of treatment. Desalination is effective in removing most or all of the active salts present, thus preserving the ceramic body from future surface spalling or, more dramatically, possible rupture of the fabric from within. The question of what other watersoluble materials are exiting during desalination is an unresolved question. The author recently addressed this issue when treating a Southwest US (Sankawi) archaeological vessel.

FTIR analysis was conducted on residues obtained by soaking samples in water and then allowing the water to evaporate. Seventeen groups of four (68 total) samples—both archaeological and modern—from a range of low-temperature firing were analyzed in this way. Microchemical testing was employed to back up FTIR interpretations. Among the interesting results were peaks representing amines and nitrates. It is thought that these represent the presence of animal and plant matter respectively, deposited post-firing. Whether the source of these materials was introduced in-use, post-deposition or both is unknown. Another interesting material found were the silicates removed from the lowest-fired modern ceramic coupons, which, together with the loss of other extracted materials, suggests a cautious approach to the submersion of archaeological ceramics.

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