Advanced 2D and 3D X-ray imaging techniques for the non-invasive and in situ analysis of pigments and degradation processes in pictorial works

The chemical alteration of artists’ pigments arises from various degradation processes, manifested as colour changes or as mechanical and structural damage within the pictorial film. These phenomena result from complex physicochemical interactions occurring within or at the surface of paint layers and are influenced by both internal and external factors, including humidity, light, temperature, pollutants, and human interventions. Since degradation products are often present only in low amounts, their detection requires highly sensitive analytical techniques, usually including synchrotron-based methods or other (micro-)invasive analyses. However, considering the need to preserve the integrity of cultural heritage objects, innovative approaches that allow the in situ and non-invasive examination of entire artworks are increasingly recommended. This PhD research aims to contribute to the development and application of advanced non-invasive X-ray imaging techniques for the in-situ characterization of pigment degradation processes in paintings. A new analytical protocol was established through the integrated use of mobile MA-XRF, MA-XRPD, and confocal XRF systems available at the XRAYLab of ISPC-CNR in Catania. Artificial ageing experiments were performed on mock-ups prepared with pigments selected based on analytical evidence from in-situ investigations of original artworks. This approach ensured that the experimental models accurately reproduced the materials and stratigraphies found in real paintings, thereby enabling the validation of the proposed analytical workflow. Overall, this work provides new insights into pigment stability and interaction mechanisms within complex pictorial matrices and demonstrates the potential of advanced mobile X-ray imaging methods for cultural heritage diagnostics.