## 3 Results and Discussion
### Laboratory Micro-Raman Results  
Raman spectroscopy was employed to unambiguously recognize all the compounds previously hypothesized through XRF and EPMA-EDS techniques. The molecular characterization of different colored areas of the painting allowed us to gain insights not only on the presence of repaintings made by the artist during the production of his artwork, but also on the existence of non-document restoration interventions based on the detection of modern pigmenting compounds. Concerning the red-colored areas of the painting (points S1, S2), Figure 5 reports a representative photomicrograph, together with the corresponding \(\upmu\)-Raman spectrum, collected on a red micro-fragment (sampled at point S1) of the painting, as example. Based on a comparison with literature [23; 24; 25; 26], the low-frequency contributions centered at \(\sim\)252 cm\({}^{-1}\) (A\({}_{\text{1g}}\)), \(\sim\)288 cm\({}^{-1}\) (E\({}_{\text{g}}\)) and \(\sim\)347 cm\({}^{-1}\) (E\({}_{\text{g}}\)) can be ascribed to the presence of vermilion (HgS), confirming our previous XRF and EPMA-EDS results. Such a compound, obtained by powdering the cinnabar mineral, assumed remarkable relevance as an artist's red paint since Roman times, sometimes combined with burnt sulfur, despite its high cost and toxicity. Interestingly, the employment of a red laser permits, in the case of vermilion, the acquisition of the best-quality Raman spectrum, since the laser frequency closely matches that associated with an electronic transition of this compound. Accordingly, resonant or pre-resonant Raman scattering phenomena are likely to occur, strongly enhancing the Raman signal by a factor of 10\({}^{2}\)-10\({}^{6}\)[27]. It is worth noting that, according to previous published papers [6; 7], the employment of vermilion by [PERSON], often in mixture with other composites such as iron oxides or red lead [13], turned out to be recurrent in the preparation of his red-reddish recipes. Interestingly, the observation of the band at \(\sim\)612 cm\({}^{-1}\) seems to confirm that vermilion was presumably mixed with poor amount of iron oxides, as also hypothesized by XRF and EPMA-EDS analysis. Furthermore, the presence of an organic compound, through the detection of contributions centered at \(\sim\)942 cm\({}^{-1}\), \(\sim\)1311 cm\({}^{-1}\) and \(\sim\)1404 cm\({}^{-1}\), can be ascribed to an organic-based binding medium, such as linseed oil or animal glue, or to a  
Figure 5: (**a**) Photomicrograph, in white reflected light, and (**b**) \(\upmu\)-Raman spectrum collected on a red micro-fragment (sampled at point S1) of the _“The Story of St. Barbara”_ painting. polishing agent used to enhance both the colors and brilliance of the painted surface. In this sense, we remark that a detailed characterization of organic binders will be the subject of a future investigation. Finally, it is worth noting that the \(\upmu\)-Raman spectrum of S2 (not reported) almost completely matches that observed in the case of S1, indicating that the aforementioned areas share the same molecular composition. As far as the orange, yellow-orange, and yellow colors are concerned (points S3, S7, S13, S24, S26, S27), Figure 6 shows a representative photomicrograph, together with the corresponding \(\upmu\)-Raman spectrum, collected on a yellow-orange micro-fragment (sampled at point S13) of the painting. The detected \(\upmu\)-Raman profile revealed, as a main feature, an intense peak at -135 cm\({}^{-1}\), together with small contributions centered at \(\sim\)333 cm\({}^{-1}\), \(\sim\)510 cm\({}^{-1}\), \(\sim\)590 cm\({}^{-1}\) and \(\sim\)735 cm\({}^{-1}\), all ascribable to Naples yellow (Ny). According to literature [28; 29; 30; 31], the strong contribution at -135 cm\({}^{-1}\), arising from the Pb-O lattice vibrations of the Ny cubic pyrochlore structure (A\({}_{2}\)B\({}_{2}\)O\({}_{6}\)O\({}^{\prime}\)), furnishes a clear indication of the employment of powdered bindheimite (Pb\({}_{2}\)Sb\({}_{2}\)O\({}_{6}\)(O,OH)) for the yellow-yellowish colorations.