Scientific investigation to compare different cleaning methods on archaeological potteryfrom the underwater site of Baia (Naples, Italy)

Abstract

The decay of pottery in underwater environments is a complex phenomenon so far poorly investigated, since a multitude of factors is involved. Degradation forms in seawater imply not only a variation in the physico-mechanical and chemical properties of the material, but also an aesthetic alteration, due to superficial deposits, which can determine to the illegibility of the artifacts. In this context, it is crucial to determine to what extent these decay factors, mainly attributable to biological growth, could affect the durability of pottery and what are the effects of cleaning procedures. Several fragments of pottery from the submerged archaeological site of Baia (Naples, South Italy) were collected and subject to different investigations. The interaction between the biological colonization and the archaeological materials was evaluated by means of stereomicroscopy and scanning electron microscopy. Then, considering that carbonatic encrustations are the main degradation products identified, some chemical and mechanical cleaning procedures have been tested for their removal. In order to check the most suitable method, some petrophysical properties were measured, such as surface roughness and ultrasonic velocity in order to evaluate change occurring in pottery properties after the removal of the degradation layers.