Study of surface of early medieval frescoes by micro-PIXE,SEM and Raman spectroscopy

Abstract

The author has studied the artist's palette and the painting techniques in the frescoes of the Longobard temple (late eighth to early ninth century) in Cividale del Friuli (Italy) and of the crypt of San Salvatore in Brescia (Italy) dated from the eighth century. High sensitivity microprobes were used such as PIXE, SEM and micro-Raman for the characterisation of materials in submillimetre samples. Information from multidisciplinary techniques revealed an unexpected richness of details and gave a clue to the economic context in which the two monuments were conceived and built. In both cases the authors found the use of common traditional materials as well as features that distinguish the two sites. Micro-PIXE analysis led to the identification of earth colours and demonstrated a few details of the surface preparation. Raman spectroscopy has identified a carbon based false blue in Cividale and degradation of carbonate into gypsum.