## 3 Results and Discussion
The characteristic peaks of beeswax are found [21], i.e., the peaks assigned to the symmetric stretching vibrations of the methyl and methylene groups at 2880 cm\({}^{-1}\) and 2842 cm\({}^{-1}\), respectively, and the peak at 1461 cm\({}^{-1}\) is attributed to the bending vibrations of CH\({}_{2}\) groups of the aliphatic chain. The strong peaks at 1435 cm\({}^{-1}\) and 1417 cm\({}^{-1}\) are due to the asymmetric and symmetric bending vibrations of CH\({}_{3}\), respectively. The comparison between the Raman spectra recorded on the A7 sample and the beeswax standard is demonstrated in Figure 5B. The arrows in the A7 sample spectrum at 1349 and 1590 cm\({}^{-1}\) indicate the features characteristic of amorphous carbon. The presence of amorphous carbon (e.g., carbon black) and beeswax both in the red and black samples confirms their use in mastic encrustations, as reported by [PERSON] et al. [14]. The XRD patterns of powdered samples A4 and A7 are displayed in Figure 6. The diffractograms show a high-intensity reflection for both analyzed samples at 20 = 21.5\({}^{\circ}\) and a medium-intensity reflection at 20 = 23.7\({}^{\circ}\), which correspond to the reflection planes  
Figure 4: (**A**) FT-IR spectra of samples A1, A4, and A7 compared with beeswax standard; (**B**) comparison of the spectrum of sample A1 and those of beeswax, spermaceti, lanolin, carnauba, and candleilla standards. Figure 5: (**A**) Raman spectra of samples A1, A2, and A6; (**B**) the Raman spectrum of sample A7 compared with the Raman spectrum of the beeswax standard. typical of beeswax fatty acid chains [24; 25; 26]. Calcite features were also identified in both samples. In addition, for sample A4, characterized by the red color, the reflection planes typical of the HgS profile [27] used in these engravings can clearly be distinguished. Through the spectroscopic techniques and XRD analysis, beeswax was unequivocally identified. On the contrary, it was not possible to discriminate the proteinaceous material with FT-IR investigation on samples A2, A3, A5, and A6. GC-MS analysis was carried out on samples A2 and A3. Both samples show fatty acids due to lipidic constituents and amino acid content. The chromatogram in Figure 7 suggests the presence of fatty acids (sample A3). Azelacic (nonanediolic acid, saturated dicarboxylic acid), palmitic (C16:0), and stearic (C18:0) acids were detected. In this sample, the value of the azelaic acid/palmitic acid ratio (A/P) is lower than 1. According to the literature [28], this value would lead to excluding the presence of drying oils. The mass spectra of derivatized azelaic, palmitic, and stearic acid are shown in Figures S2-S4. Figure 8 shows the amino acid chromatographic profile of sample A2, taken from the dark-colored material. The amino acid mass spectra are shown in Figures S5-S16. Figure 6: XRD on A4 and A7 samples. * = beeswax, \({}^{\circ}\) = cinnabar [JCPDS, card N\({}^{\circ}\) 42508], C = calcite [JCPDS, card N\({}^{\circ}\) 5586]. Figure 7: Chromatogram of fatty acids of sample A3 and dark color from letter R of S:MA/RIA. C9 = azelaic acid, C16 = palmitic acid, C17 = heptadecanoic acid (internal standard), C18 = stearic acid. To characterize the proteinaceous binding media, the percentage content of amino acids was compared to those from a dataset of 61 reference samples of egg (whole, egg white, egg yolk), casein, animal glue, and a mixture of them, considered the most widespread proteinaceous binders in the Western tradition, belonging to the reference collection of the _Opificio delle Pietre Dure_ in Florence, Italy [29]. Using these data as variables, multivariate statistical analysis, namely, principal component analysis, PCA [30], was carried out on the correlation matrix of the relative percentage contents of eight amino acids (aspartic acid, glutamic acid, proline, hydroxyproline, phenylalanine, alanine, glycine, and leucine) [31]. The PCA score plot is described in Figure 9.  
The first two components, PC1 and PC2, account for 61.67% and 23.70% of the total variance, respectively.