## 5 Conclusions  
The findings of this study demonstrate that the artificial ageing protocol (AAP) exerts a significant impact on the organic binders used to reconstruct the original polychromy layers (Band A), namely, Arabic gum and animal glue. In contrast, the inorganic pigments employed in the samples, azurite, vermilion, ochre, and the mixture of artificial ultramarine blue with titanium white, did not undergo detectable chemical alterations. The observed changes in these pigments were exclusively chromatic in nature, indicating that the degradation processes primarily affect the optical properties of the materials, rather than their molecular structure. * Chromatic Level: In the case of the original polychromy (Band A), azurite bound with animal glue exhibited a marked loss of lightness (L* parameter), which can be attributed to the effects of relative humidity during the ageing process. Vermilion, on the other hand, showed a reduction in both lightness and, more notably, chroma (saturation of the red component) when combined with either Arabic gum or animal glue. This behavior is associated with combined photodegradation and oxidation processes induced by exposure to ultraviolet light and high humidity conditions. In the oil-based overpaint layers (Band B), the ochre pigment demonstrated greater stability against artificial ageing, a result likely due to its mineral composition. In contrast, the mixture of artificial ultramarine blue with titanium white proved more susceptible to degradation, showing sensitivity to the acidity of the binder, which highlights its lower resistance under simulated deterioration conditions. * Chemical Level: Fourier Transform Infrared Spectroscopy (FTIR) and Gas Chromatography coupled with Mass Spectrometry (GC-MS) analyses allowed for the characterization of chemical changes in the binders. In the case of Arabic gum, a reduction in reflectance peaks corresponding to hydroxyl and stretching of conjugated C=C double bonds were observed; however, no modifications were detected in its monosaccharide composition, suggesting that the changes are primarily due to a drying process rather than structural chemical alteration. Therefore, this is a physical change due to the loss of hydration water, rather than a chemical one. For animal glue, the analysis revealed both chemical and physical alterations. Fourier Transform Infrared Spectroscopy (FTIR) showed a decrease in the amide I and II bands, indicating partial denaturation of the protein matrix. However, Chromatography coupled with Mass Spectrometry (GC-MS) analysis revealed a 22% preservation of the main amino acids, suggesting no significant degradation of the peptide chains. The discrepancy between both methods points to surface-level degradation or conformational changes. Additionally, cracks and fissures were observed, likely caused by heat and UV radiation, confirming physical deterioration of the binder as well. In linseed oil, the analyses identified advanced oxidation and polymerization processes, evidenced by the appearance of new hydroxyl groups and a decrease in carbonyl and alkane groups. Additionally, the formation of dicarboxylic fatty acids such as sebac, azelaic, and suberic acids, typical markers of aged oil, was confirmed by Fourier Transform Infrared Spectroscopy (FTIR) and Chromatography coupled with Mass Spectrometry (GC-MS). These chemical changes resulted in visible physical alterations, including craquelure. Therefore, linseed oil exhibited significant chemical and physical degradation following artificial ageing. Regarding the removal of overpaint layers, the conclusions drawn from this study indicate that Treatment 1, based on a mixture of heptane and acetone, was highly effective in dissolving the oil-based repaint, including its aged form. This effectiveness is attributed to the neutral solvents acting solely through solubility parameters without affecting the original layer.