## 3 Results and Discussion
### Lacunae, Retouched and Restored Areas  
An extensive presence of paraffin was found in all the samples taken from Panels A, D and E, characterized by a series of linear alkanes with an number of carbon atoms higher than 25, and with a \"Gaussian\" shape [23; 30] (Figure 7). Interestingly, paraffin was also found in samples taken from Panel E for the characterisation of the original binder, although it showed a different chromatographic profile and was particularly abundant in samples SG_30 and SG_44 (Figure 8). Paraffin was detected in all samples from Panel A, with the exception of sample SG_43. Figure 6: Extracted ion chromatogram of the fragment ion \(m/z\) 85, which is abundant in the mass spectra of linear aliphatic hydrocarbons. Cn indicates a linear aliphatic hydrocarbon with n carbon atoms. A glycerolipid material was detected in samples SG_18A, SG_27A, SG_28A and SG_32, based on the identification of saturated monocarboxylic fatty acids (palmitic and stearic) and dicarboxylic acids (sebacic, azelaic and suberic acids) (Figure 6). The chromatographic profile, and in particular the relatively high content of dicarboxylic acids, indicates the presence of a sicactive oil [29]. Moreover, SG_18A and SG_32 still present oleic acid, a  
Figure 8: Chromatographic profiles of the ion extracted with \(m/z\) 85 for samples SG 44 and SG 30. Cn indicates a linear aliphatic hydrocarbon with n atoms of carbon. Figure 7: Total Ion Current (TIC) Chromatogram of sample SG_18A after methyl ester derivatization (ME). IS: internal standard: nonadecanoic acid–ME; di-FA9: azelaic acid–ME; di-FA10: sebacic acid–ME; FA14: myristic acid–ME; FA16: palmitic acid–ME; FA18: oleic acid–ME; FA18: stearic acid–ME; Cn linear aliphatic hydrocarbon with n atoms of carbon. monousaturated fatty acid generally still present in not completely mature oil paint films. Its presence suggests that the drying oil found in the samples is most likely a later material rather than an original one used by [PERSON]. Myristic acid, a saturated fatty acid naturally present in many vegetable lipid materials, is ubiquitous. Its relative abundance in the chromatographic profile strongly suggests that it is not derived from the drying oil, but it could be present as an additive (such as a surfactant or emulsifier). A plant resin of the Pinaceae family was identified in samples SG_27 (both yellow and orange) and SG_32, based on the detection of abietic acid and its oxidation products [21] (dehydroaietic acid, 15-oxo-dehydroaietic acid and 7-oxo-dehydro-abietic acid). This terpenoid material, not traditionally used as a binder in wall paintings, could be present as an additive of the binder used for retouching or in oil-resinous coatings. The presence of abietic acid also emphasises that the painting is relatively fresh and therefore not of the same period as the creation of the painting cycle. Synthetic polymers were also found. In particular, an oil-modified alkyld-based resin was identified in samples SG_28A and SG_45A, based on the detection of orthophthalic acid, benzoic acid, glycerol and a drying oil [12]. An acrylic-styrene resin was identified in sample SG_21B, thanks to the main presence of styrene, butyl acrylate, n-butyl methacrylate and \(\alpha\)-methylstyrene [31,32]. These synthetic materials are likely present as binders of the paints used for the reintegration, being amongst the most used contemporary paints. For the identification of possible proteinaceous and polysaccharide fractions remaining from the original binder, the samples were also subjected to analysis with Py-GC-MS in Double Shot mode (350-650 \({}^{\circ}\)C) as described in the literature [33]. The analyses were not conclusive, however, as the typical markers of the proteins present in casein or egg-based paints were not detected. This aspect could be linked to natural aging and cross-linking processes, as well as to the interference due to the inorganic component of the samples and the many materials used in restoration and painting reintegration.