Laser-induced breakdown spectroscopy (LIBS) and Raman microscopy were used for the identification of pigments in wall painting. Raman spectroscopy, which provides the molecular 'fingerprint' of the compound, is nowadays widely used by the archaeometry community, especially for pigment analysis. LIBS, which provides the elementary composition of samples, is a rapid noncontact method, enabling layer-by-layer analysis through a precise laser ablation of the sample. This work deals with the behavior of pigments after a LIBS analysis, by trying to identify the compounds before and after the laser shot. Six commercial pigments prepared with the fresco technique were investigated: ultramarine blue, red lead, charcoal, a yellow and a red ochre, and a green earth. Raman spectra, acquired on the sample surface and in the crater induced by LIBS analysis, were compared. The results show that these pigments are well recognized after a LIBS measurement. The analysis of green earth illustrates that the combination of these two techniques gives complete information from a sample.

Laser Induced Breakdown Spectroscopy (LIBS) can be successfully used for cultural heritage applications, such as pigment and stone identification or archaeological metal characterisation. In this work we focus on the study of wall painting pigments. Two methods of signal analysis are tested. The first one is based on spectral lines identification in order to detect characteristic chemical elements. In the second one, we apply chemometrics models (SIMCA and PLS-DA) to a pigment reference database. Results show the improvement of pigments identification obtained with the multivariate analyses approach. This work includes laboratory study and on site validation.