Laser induced breakdown spectroscopy for the analysis of archaeological dyes from Licata (Sicily)

The materials used in the decoration of ancient roman building have been the object of investigation by means of non-destructive and micro-destructive techniques. A number of spectroscopic analysis, laser-induced breakdown spectroscopy (LIBS), micro-Raman, and micro-Fourier transform infrared spectroscopy, on three fragments of architectural decorative painted elements from an excavation near Licata (Sicily), have been performed with the aim to identify the pigments composition and their interaction with the matrix. The fragments have been dated by the archaeologists to late III B.C and the end of I B.C (such an attribution agrees well with historical information about the site) and showed four different coloration: red, yellow, light blue, and black. LIBS, emerged only in the last years as a very promising tool for the analysis and the characterization of elemental composition of a large variety of objects in the field of cultural heritage. The technique is based on the spectroscopic detection and identification of the light emission from excited atomic species in the plasma produced by a high energy laser pulse focused onto the surface of the sample. Although LIBS can give information about the pigments' atomic composition, structural ones have been gained with micro-Raman spectroscopy. Thus, the combined LIBS and micro-Raman measurements allowed the pigments' identification for all of the four colorations.