## 3 Results
### FTIR-Arr  
The main peaks in the FTIR spectra of the painting sample surfaces are listed in Table 9. C-H stretching vibrations of the -CH\({}_{3}\) and -CH\({}_{2}\) groups were located in the 2950-2800 cm\({}^{-1}\) area. The C=O double bond stretching vibration of carbonyl groups was present around 1745 cm\({}^{-1}\). The peaks in the 1470-1200 cm\({}^{-1}\) area are associated with the CH bending of CH\({}_{2}\) and CH\({}_{3}\). Due to CH\({}_{2}\) rocking vibration and C-O ester group stretching vibration, the fingerprint region was located between 1250 and 700 cm\({}^{-1}\). The FTIR spectra (Figure 7) acquired from Methyl caprate, Methyl laurate, Methyl lyristate, and Methyl oleate show the same characteristic peaks at 2921, 2852, 1458, 1434, 1358, 1239, 1195, 1169, 1009, 719, 711, and 700 cm\({}^{-1}\). Similarly, the Methyl palmitate, Methyl stearate, and Agnique ME have peaks at 2951, 2914, and 2847 cm\({}^{-1}\), albeit with different \begin{table}
\begin{tabular}{c c c c c} \hline
**Unaged Acrylic** & **Unaged Oil** & **Aged Acrylic** & **Aged Oil** & **Assignment** \\
**Painting Surface** & **Painting Surface** & **Painting Surface** & **Painting Surface** & **Assignment** \\ \hline  & 3010 & & 2923 & CH\({}_{3}\) stretch \\ \hline  & 2897 & & 2852 & CH\({}_{2}\) stretch \\ \hline
1712 & 1746 & 1735 & 1739 & C=O \\ \hline  & 1655 & & 1652 & C=C \\ \hline
1474 & 1408 & 1403 & 1408 & CH\({}_{3}\) Asymmetric bend \\ \hline
1240 & & 1227 & & C–O ester bond \\ \hline
1170 & & 1155 & & CCH (C=C) \\ \hline
1150 & & 1120 & & C–O ester bond \\ \hline  & 1021 & 1013 & 1021 & C–O ester bond \\ \hline  & 872 & 870 & 872 & \\ \hline  & & 753 & & C–H2 \\ \hline
710 & 711 & 710 & C=C–H (cis) bend \\ \hline \end{tabular}
\end{table} 
Table 9: IR assignment of the peaks collected on the painting material (unaged and aged). intensity to the first, while in the Methyl stearate the peak at 1741 cm\({}^{-1}\) was not present. Methyl stearate and Agnique ME have peaks at 1471, 1462, 1343, 1279, 1241, 1446, 1109, 1059, 1023, 964, 839, 731, and 718 cm\({}^{-1}\). Methyl palmitate was instead characterized by numerous peaks in the region between 1500 and 1000 cm\({}^{-1}\); specifically, the peaks were at 1472, 1462, 1434, 1381, 1309, 1286, 1264, 1241, 1219, 1196, 1167, 1099, 883, 729, and 719 cm\({}^{-1}\). Regarding the coatings, some variation in the IR spectrum after the aging process was observed only for Regalrez 1094. In particular, the aged Regalrez spectrum is characterized by increasing absorption of the hydroxyl region between 3650 and 3050 cm\({}^{-1}\), suggesting the formation of new O-H bonds. Furthermore, a new absorption band appears at 1712 cm\({}^{-1}\) with the appearance of new C=O bonds. Additionally, there is a slight increase in absorption at 1200 cm\({}^{-1}\), indicating the appearance of C-O bonds. These structural changes suggest that upon irradiation, the hydrogenated hydrocarbon resin undergoes photo-oxidation with the generation of new oxidation products. There is an observable decrease in absorption for the C-H stretching and bending regions, 3000-2750 cm\({}^{-1}\) and 1500-1400 cm\({}^{-1}\), respectively. It is uncertain exactly why these bands decrease so much in intensity, but it could be related to photo-oxidation of the material [37]. To define the presence of residue of FAME gels, spectra were acquired on the cleaned canvases; on the coated canvases, on the canvases after the cleaning treatment, and on the spectra of all the solvents and the polymer used for the formulation of the gels (PHB) (Figures 8-11). Considering the overlap of the same peaks relative to functional groups present in all the substances, to define FAME gel residues, more consideration was given to the \"Fingerprint\" region. This region represents peculiar characteristics of the substance, while the other regions of the spectra are related to functional groups that may be present in different kinds of molecules; in this study, this was the case for the non-polar coating and the FAME.