## 3 Results and Discussion
### Characterizations of Oil Painting After Varnish Removal
#### 3.3.2 Gas Chromatography-Mass Spectrometry (GC/MS)
The first application, which is less invasive, however, requires the surface to be flat for a homogeneous action; the second always proves to be more effective due to the optimal contact that can be obtained even on a three-dimensional surface, but it involves a temperature input (generally 45-50\({}^{\circ}\)) that may not be compatible with certain organic materials and layers. Removal of the varnish occurred in all treatments, without noticeable difference from case to case. Table 6 shows that leaching from the application of the neutral-pH rigid pad (sample 1) is comparable to that produced by xanthan gum (sample 3) and can be lowered to the lowest amount in these tests on a D5-saturated surface (sample 1D). However, not surprisingly, the degree of this leaching interaction jumps to one of the highest levels in this study with the warm application of the semi-solid emulsion (sample 2). Even in this case, thanks to its low volatility, D5 is still able to perform some barrier action and mitigate leaching (sample 2D), which remains high. This trend is confirmed with the higher pH hydrogels: strong leaching on the unprotected surface as pre-formed pad (sample 4), even stronger from the semi-solid application (sample 5). The protective barrier action of D5 (samples 4D and 5D) appears less effective, particularly at high pH (sample 5D). \begin{table}
\begin{tabular}{c c c c c} \hline
**Analyte** & \multicolumn{4}{c}{**Samples**} \\ \hline  & 7 & **7D** & **8** & **8D** \\ \hline  & \multicolumn{4}{c}{(\(\mu\)g/100 \(\mu\)g)} \\ \hline C9 di & 0.29 (2) & 0.26 (7) & 0.2 (6) & 0.25 (9) \\ \hline C14 & 0.02 (1) & 0.02 (1) & 0.02 (1) & 0.02 (1) \\ \hline C15 & 0.01 (0.5) & 0.01 (0.5) & 0.01 (0.5) & 0.01 (0.5) \\ \hline C16 & 0.31 (3) & 0.32 (8) & 0.31 (9) & 0.42 (3) \\ \hline C18:1 & 0.03 (2) & 0.04 (1) & 0.04 (3) & 0.04 (1) \\ \hline C18 & 0.26 (2) & 0.34 (3) & 0.30 (6) & 0.37 (2) \\ \hline C20 & 0.01 (0.5) & 0.03 (1) & 0.02 (1) & 0.02 (1) \\ \hline C22 & 0.01 (0.5) & 0.03 (1) & 0.02 (1) & 0.01 (0.5) \\ \hline TOT & 0.94 & 1.04 & 0.91 & 1.13 \\ \hline \% present & 65 & 72 & 63 & 79 \\ \hline \% removed & 35 & 28 & 37 & 21 \\ \hline \end{tabular}
\end{table} 
Table 5: Polyacrylate gel tested on samples 7, 7D, 8, 8D, with and without pre-saturation with D5. Standard deviation is reported in parenthesis. Further tests were conducted based on two considerations. First, concentrations around 2% of BAl produce surfactant-free emulsions that are already sufficiently effective in many cases for the removal of varnishes (and, more generally, organic film-forming substances) that are not excessively aged. Secondly, this study has shown that even saturation alone with siloxane D5 produces a certain leaching on a relatively recent oil paint. Combining these two pieces of information, it was decided to evaluate the interaction of a surfactant-free emulsion composed as follows: pH 7 phosphate buffer gelled with 3% Vanzan NF-C(tm), with 2% BAI. The emulsion was applied without pre-saturation of D5. To obtain even more significant data from a practical point of view, this application was compared with the removal of the varnish obtained with organic solvents, specifically ethyl acetate and a mixture of 40% acetone in isooctane, applied through a cotton swab, working under UV light to achieve complete removal of the varnish. The former solvent combines characteristics of moderate toxicity with excellent solvent power towards natural and synthetic resins; the latter solvent mixture is commonly used for the removal of spirit varnishes made from natural terpenoid resins. Table 7 reports the result of the applications. The results show that reducing the concentration of BAI in the emulsion effectively decreased leaching: 24% compared to 27% for the same treatment with 5% alcohol (sample 3).