## 3 Results and Discussion
### The State of Conservation of the Painting  
From the spectrum obtained by analyzing the S_3 sample by Fourier transform infrared spectroscopy (FT-IR), peaks emerged at 2982, 2952, 1724, 1634, 1446, 1385, 1233, 1138, 1023, 968, 859, 753, 514 and 494 cm\({}^{-1}\). The FT-IR spectrum obtained was then compared to that of Paraloid B72, a commercial acrylic resin often used in the conservation field. The overlapping of the two spectra is clearly visible in Figure 11, confirming the organic nature of the substance. The hypothesis put forward that indicated it was an act of vandalism was denied during the restoration phases by the discovery of the impression of a gauze weave. This made it possible to assume that it was actually an undocumented intervention, carried out in the paste with a conservation purpose to temporarily preserve the pictorial film through the application of a facing. The carbonic composition of the diffuse whitish veil on the pictorial surface was confirmed by FT-IR, carried out on sample S_5, taken from a thicker concretion developed at  
Figure 11: FT-IR spectrum of the substance upon the pictorial film (red line) compared to that of the Paraloid B72 (green line). a plaster fracture, which produced a spectrum showing only the peaks of calcite (1415, 873 and 712 cm\({}^{-1}\)) and silicates/clay minerals or products of their alteration (about 960 cm\({}^{-1}\)). Raman spectroscopy, on the other hand, made it possible to confirm the hypothesis put forward for the black-colored coherent deposits present on the pictorial pieces of both trunks, which, from macroscopic and microscopic observation, appeared to consist of burnt material. Bands were detected at 223, 282, 710 and 1085 cm\({}^{-1}\), overlapping with calcite, and at 1343 and 1586 cm\({}^{-1}\), corresponding to carbon black. In this case, it would not be a pigment, however, but a carbonaceous deposit, presumably due to the prolonged contact of the surface to an open flame. Considering the acts of vandalism to which the painting has been subjected, it was thought that these deposits might be the trace left by a fire, set to damage the painting on purpose. However, the presence of soot is exclusively limited to the internal area of the semi-dome, while there are no traces on the wall structure. It could, therefore, be hypothesized that the dark deposit originated from before the collapse of the building, and it is most likely caused by the use of torches or votive lamps close to the surface that were used in ancient times to illuminate the painting and the environment. Considering the outdoor environment to which the mural painting is exposed and with the aim to plan the most appropriate conservative strategies, the soluble salt in solution inside the plaster (samples S_6 and S_7) was investigated by ion chromatography (IC). The results of both the cationic and anionic species concentrations (in ppm) are reported in Table 5. The results show that the concentrations detected are not relevant, so it can be stated that the mural painting does not suffer degradation phenomena attributable to salt decay. The concentrations of the cations Na\({}^{+}\) and Ca\({}^{2+}\) and of the anion SO\({}_{4}\)\({}^{2-}\), which are higher in plaster sample S_6, presumably indicate the presence of sodium or calcium sulfates, on the origin of which a variety of hypotheses could be made, given the outdoor conditions to which the artifact is exposed, which allows both capillary rise and percolation of meteoric water, and the presence of biological species capable of depositing salts on the substrates they colonize. However, very small amounts have been detected, for which it is difficult to assume a correlation with the severe forms of degradation observable in the mural painting.