From Mock-ups to Artworks: Development and Application of Specific Analytical Methodologies

The main scope of this doctoral thesis was the evaluation of micro- and non-destructive techniques applied to artwork characterization. The need to study capabilities and limitations of these techniques arises from their increased use in the field of Cultural Heritage, without sufficient previous evaluation. Oil paintings, photographs and a large metal alloy object were investigated as representatives of three important artwork categories. Chapter 1 is an overview of the material properties of the artwork types investigated. Chapter 2 presents the study of the detection limits and the evaluation of the reproducibility of SEM-EDS and micro-FTIR in the application to paint layer investigation. Despite the good quality of the obtained spectra and the high sensitivity of these techniques, the low amount of material and the distribution of the different compounds across the sample made it difficult to obtain representative results. These problems could partially be overcome by analysing large areas rather than spots for SEM-EDS and performing replicates on different points of the specimen for micro-FTIR. Moreover, the capacities and limitations of midIR-FORS when employed to the examination of oil paintings were evaluated. It has been proved that the detection limits for this kind of set-up are especially high, although the major areas investigated permit to achieve better reproducibility and more representative information with respect to micro-FTIR. The physical feature/roughness of the analysed surface is a critical factor that may cause distortions in the spectra and be responsible for a decreased signal-to-noise ratio. It was achieved the creation of pigment mapping of oil paintings by means of midIR-FORS and multivariate methods. In a comprehensive study, the optimal data pre-processing methods as well as a protocol for the application of PCA and PLS-DA for FORS spectra modelling have been proposed. Furthermore, these methods were successfully applied to investigate and prove the influence of the surface ...