Degradation studies on different pigments and binders: new approaches to diagnostics in cultural heritage

Studying the state of degradation, alteration and conservation of an artwork is the starting point of a restoration process. This first step is commonly known in the field of cultural heritage as "diagnostics". A careful diagnosis allows choosing the best restoration approach for a sample under examination. The diagnostics of an artwork permits not only a complete characterization of materials realized by an artist, but also the identification of the degradation products generated over time. The main intent of this work is to expand the diagnostic research both from a descriptive point of view for the degradation process of the painted surface, and from the point of view of new approaches and methodologies for diagnostics. For what concerns the first one, we worked with two main purposes: kinetics studies in the case of San Giovanni white with the help of a non-invasive technique (Raman spectroscopy), and the characterization of the degradation path and individuation of the respective alteration products in the case of Red vermilion and Cd-pigments, always favouring the choice of a non-destructive techniques, conventional or not, such as non-linear optics. Regarding the development of new approaches and methodologies, we studied the photo-acoustic method coupled with SORS (Spatially Off-set Raman Spectroscopy) as a new tool for stratigraphy analyses of frescoes. This work is carried out in collaboration with the research centre FORTH (Crete) and it has been tested on artificial frescoes mock-ups and on real frescoes fragments, in order to obtain compositional information and stratigraphic imaging on the samples.