## 3 Results and Discussion
### Characterizations of Oil Painting After Varnish Removal
#### 3.3.2 Gas Chromatography-Mass Spectrometry (GC/MS)
Considering that 5% was used in these tests, only a small part of this quantity is actually emulsified, while the majority is dissolved in the dispersing phase; the latter could act like a hydroalcoholic solution, with solvent power and interactions difficult to predict. On the surface saturated with D5, however, the siloxane could act as a dual barrier complete towards the aqueous phase and partial (even if only for a few ppm) towards BAI. The results in Table 4 may support this reasoning: leaching on the original surface (sample 3) is obviously less than with the pure alcohol, but it is still significant, and it becomes considerably reduced by the silicone barrier (sample 3D). As expected, raising the pH of the gelled aqueous phase (sample 6) to 8.5 increased the rate of removal of the varnish but also the leaching interaction, even if only slightly. More ionizing action on the resin molecules increases their hydrophilic character, thus contributing to faster removal of the varnish and, as side effect, stronger interaction of the active solvent with the paint layer. The barrier action of the silicone solvent (sample 6D) remains effective even at this pH value, almost halving the leaching interaction. In this set of tests, the base used to gel the polyacrylic/polyacrylate Pemulen TR2(tm) was triethanolamine, a commonly used ingredient in these formulations for removal of film-forming materials. Unlike inorganic bases, this is also a high-polarity solvent: [PERSON] solubility parameters, \(\delta\)d 17.3 \(\delta\)d 22.4 \(\delta\)h 23.3. In addition to pH, it generally makes a large contribution to the solvent power of the corresponding hydrogels or surfactant-free emulsions. This can be seen in the results in Table 5: higher leaching on the original surface as compared to the xanthan emulsions, both at pH 7 (sample 7 vs. sample 3) and at pH 8.5 (sample 8 vs. sample 6). Also, in this case, the D5 pre-treatment of the surface mitigates leaching, but the protection is less effective than before, particularly at neutral pH. Removal of the varnish was achieved in all samples, without appreciable difference from treatment to treatment. \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multicolumn{1}{c}{**Analyte**} & \multicolumn{4}{c}{**Samples**} \\ \hline  & **3** & **3D** & **6** & **6D** \\ \hline  & \multicolumn{4}{c}{(**Hg/100 \(\mu\)g)**} \\ \hline C9 di & 0.23 (4) & 0.34 (2) & 0.23 (6) & 0.28 (2) \\ \hline C14 & 0.03 (1) & 0.03 (1) & 0.05 (2) & 0.02 (1) \\ \hline C15 & 0.01 (0.5) & 0.02 (1) & 0.03 (4) & 0.01 (0.5) \\ \hline C16 & 0.35 (6) & 0.39 (5) & 0.33 (7) & 0.41 (9) \\ \hline C18:1 & 0.05 (1) & 0.06 (1) & 0.01 (1) & 0.02 (1) \\ \hline C18 & 0.36 (9) & 0.39 (2) & 0.26 (6) & 0.42 (8) \\ \hline C20 & 0.02 (1) & 0.01 (0.5) & 0.06 (2) & 0.02 (1) \\ \hline C22 & 0.01 (0.5) & 0.01 (0.5) & 0.02 (1) & 0.02 (1) \\ \hline TOT & 1.06 & 1.25 & 0.99 & 1.2 \\ \hline \% present & 73 & 86 & 69 & 83 \\ \hline \% removed & 27 & 14 & 31 & 17 \\ \hline \end{tabular}
\end{table} 
Table 4: Treatments with xanthan at pH 7 (3, 3D) and pH 8.5 (6, 6D). Standard deviation reported in parenthesis. Surfactant-free emulsions can also be prepared in rigid form, using dispersed phases made from thermo-reversible hydrogels of agarose or agar [7; 32]. This strategy can be decisive for certain treatments, when it is particularly important to better localize the action and to restrict the diffusion of the aqueous medium and the emulsified solvent on sensitive surfaces. The polysaccharides agarose and agaropectin have a certain emulsifying capacity, although decidedly lower than xanthan gum and polyacrylates. However, it is possible to insert quantities of BAI equal to 10-15% by volume compared to the aqueous phase into the emulsion, also depending on the quantity of gelling agent used. Furthermore, these hydrogels/surfactant-free emulsions always offer the double possibility of application: as a preformed solid pad or in semi-solid form.