## 3 Results and Discussion
### Results of Cleaning Tests on Mock-Ups  
The results of the artificial aging experiments reveal a slight phenomenon of cracking on the surface of the mock-ups, which bears a resemblance to the cracking observed in _Spitz-Rund_. However, the extent of this alteration appears to be less pronounced on a macroscopic scale in the artificially aged mock-ups. Our findings indicate that while the alterations observed in the artificially aged mock-ups are similar to those of the painting, the severity of the cracks is reduced. This suggests that the aging process used in the experiments may not fully replicate the long-term environmental and material conditions of the original paint layers. Future work will need to address this limitation by refining the aging protocols to more closely match the conditions under which natural aging occurs, thereby enhancing the fidelity of the artificial aging process and improving the correlation between experimental and case studies. Before proceeding to highlight cleaning test effects, it is important to report how few differences in solvent sensibility were observed between the mock-ups of the three series. In any of the tests, the solvent action had caused a complete removal of the varnish layer to the point of altering the underlying paint layers, so no differences in behavior between the three series could be verified. It is possible that similar effects to cleaning tests depend on the kind of raw materials employed or the way in which the layers were prepared. Moreover, the aging may not have been sufficient to induce an interference between one layer and the other. In addition, tests made by rolling the cotton swab with pure solvents have shown that paint layers of mock-ups without varnish film have a tendency to swell with low polar solutions. At first, the removal tests showed that water, also by setting the pH or the ionic strength, had no effect on the ketone resin, so any water-based methods have not been taken into account. Table 4 shows the main results of cleaning tests made on the Type 3 mock-ups, where the assessments were carried out by comparing Visible diffuse light photography and UV light photography. Based on these results, micro-samples of some of them were taken for cross-section analyses. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Localization** & **Sample** & **Type of Sample** & **Drying Oil** & **Natural** & **Ketone** \\  & **Number** & **Type of Sample** & **Drying Oil** & **Resin** & **Resin** \\ \hline  & 01 & Multi-layered sample, paint and varnish layers & ++ & ++ & +++ \\ \hline  & 02 & Multi-layered sample, paint and varnish layers & ++ & ++ & + \\ \hline  & 03 & Multi-layered sample, paint and varnish layers & ++ & + & + \\ \hline \hline \end{tabular}
\end{table} 
Table 3: List of micro-samples investigated on _Spitz-Rund_. The symbols + refer to semi-quantitative quantification of components in samples: (+) low amount; (++) medium amount; (++) high amount. & Few paper fiber residues on the surface. Adding a next mechanical action through using the sponge, the cleaning effect is good. \\ \hline T11 & & +++ & Good softening of the varnish film through using the tissue. The next step with the sponge supports the resin removal. \\ \hline T12 & & +++ & Uncontrolled dispersion of the solvent that has a high interaction with the paint layers. The paper leaves some fiber residues and the surface after cleaning is uneven. \\ \hline T13 & & +++ & Slight softening of the varnish film, partially absorbed by the gel. The test causes some bleaching on the surface. \\ \hline T14 & & +++ & Good softening of the varnish film. The surface after cleaning is even. \\ \hline \hline \end{tabular}  
* Symbols express the effectiveness of the cleaning test in a range from (+) acceptable to (++) good to (+++) very good.