A combined 3D surveying, XRF and Raman in situ investigation on The Conversion of St Paul painting (Mdina, Malta) by Mattia Preti

This paper presents the results of three different approaches applied to the newly-restored titular painting entitled The Conversion of St Paul , the main altarpiece in the Mdina Cathedral in Malta. This large, dramatic painting is the work of the Baroque artist, Mattia Preti, known as il Cavaliere Calabrese . Here, we focus on the results of the digital photogrammetric survey that adopts image-based approaches for 2D/3D model reconstruction. The model was used to quantify important features of the painting as well extensions of the areas restored. In addition, portable X-ray fluorescence and Raman spectroscopies were used to non-destructively identify the nature of the painting materials, at the elemental and molecular spatial scales, respectively, with the ultimate goal of reconstructing the colour palette of the artist. The 3D model developed here could be applied to other paintings of Preti to conduct comparisons between different measurements in the paintings, with the main goal of clarifying the technique used by the artist. This information, along with the characterisation of the materials used, is crucial for the reconstruction of the historical–geographical context of the artwork, since specific pigmenting agents and media tend to represent the stylistic expression of an artist or an epoque.