Characterization of the pigments of Siceliot pottery decoration: the case of Centuripe ceramics

Abstract

Abstract: Two Centuripean vases dated back to the 2th century B.C were analyzed using complementary non-invasive and non-destructive portable XRF and Total Reflectance FTIR spectroscopies. The vases are of great importance since they represent a rare expression of the Hellenistic period. The two vases, a “Pyxis” and a “Lebes Gamikos” decorated with figures of different typology, are exhibited in Salinas archaeological museum in Palermo-Italy. The Pyxis vase consists of three parts: the body, a removable lid and a decoration egg. The Lebes Gamikos vase consists of the body and a non-removable lid. The body and the lid of Pyxis vase as well as the body of Lebes Gamikos vase are decorated with different painting scenes. The state of conservation of the paintings is very poor for both vases. The aim of the investigation was to identify the used pigments for the decorations and the painting technique, to recognize the retouched areas and, eventually, to acknowledge the authenticity of these vases. XRF and IR analysis were performed on selected points representative of different colored areas. The analyzed points were selected from original and restored areas whose identification was performed with the aid of a restorer. The decoration resulted by the superimposition of three layers. The inner one is a white layer composed mainly by calcium carbonate and calcium sulfate. The middle layer, red colored, contains iron oxides. The outer layer is patterned with pigments that are common in the Hellenistic period. In some areas, modern pigments were also identified. The decorations were made using a tempera technique, as inferred by the identification of proteins residues by reflectance IR spectroscopy. One of the most interesting results concerns the identification of two calcium sulfate phases: the gypsum and the bassanite that undergo phase equilibrium promoted by temperature and humidity. The two phases are located only in some areas of the surface while in other only gypsum was identified. Additional investigations are necessary in order to verify if the presence of gypsum or gypsum and bassanite could constitute a criterion to discriminate original areas from later restoration or falsification.