## 3 Results and Discussion
### Removing Varnish on Spitz-Rund  
Based on the cleaning procedure assessed on the mock-ups, we intended to follow the same approach for the cleaning of _Spitz-Rund_. The starting point was the evaluation of the solubility of the non-original varnish by applying pure solvents on the surface through a cotton swab. By gradually increasing the polarity force of solvent blends, the range of swelling of the ketone varnish was confirmed to be included in the range previously considered [3]: indeed, due to the natural aging of the artwork, the ketone varnish of _Spitz-Rund_ showed a tendency to be softened with solvent blend with an Fd lower than 87. Since the solubility action of ethanol on the painting proved to be more effective than other pure polar solvents or nanostructured fluids, it was tested and loaded into three kinds of gelling systems, as listed below:  
1. Nanorestore Gel(r) Peggy 5 + ethanol/water (1:1). 2. Nanorestore Gel(r) MWR + ethanol. 3. PVA-borax gel + 20% \(w/v\) ethanol. Although the PVA-borax gel and Peggy 5 gel did not provide optimized results on mock-ups, they were included again among the products tested directly on the painting since they proved to be more respectful of the surface compared to other systems previously tested. Test 2 (Nanorestore Gel(r) MWR + ethanol), as already assessed on mock-ups, was the most effective in removing varnish film without bleaching (as happens for Test 1, Nanorestore Gel(r) Peggy 5 + ethanol/water (1:1)) or leaving residues (Test 3, PVA-borax gel + 20% \(w/v\) ethanol). The loaded gel is kept on the surface only for 20-30 s and then removed by delicately peeling it with tweezers. The time of application was shortened in comparison to the tests on mock-ups to further ensure the safety of the artwork. Another advantage of the use of Dry gel is that it can be cut down following the outline of the colored shapes of the painting, varying the time of application according to each specific paint layer. Thanks to the combination of the swelling power of the alcohol  
Figure 7: Cross-sections under UV light of two cleaning tests on mock-ups. Numbers identify the layers; (1) pink paint layer, (2) natural resin film and (3) ketone-based varnish. (**a**) Figure shows the cross-section taken from Test 8 after cleaning. Arrows indicate the alteration areas of the shellac-based film; (**b**) Figure shows the cross-section taken from Test 14 after cleaning. and the capillary absorption capacity of the nanostructured system, a good removal of the ketone varnish was successfully achieved. After the application of the gel, the surface was accurately observed with the support of non-invasive survey instruments such as a 3D microscope. The images acquired (Figure 8) show that the original paint surface was unaltered, but there still were several varnish residues. Based on these considerations, a second cleaning step with the use of a Blitz-Fix(r) sponge was applied. However, the result obtained was not fully satisfactory, and to reach a complete paint removal, another step was added. A cotton swab loaded with a low-polarity solvent mixture (iso-octane: ethyl alcohol = 80:20 \(v/v\)) was rolled on the surface. Furthermore, it has to be kept in mind that the Blitz-Fix(r) sponge could not have been used for this purpose because it does not support apolar solvents. The combination of these steps resulted in a satisfactory outcome upon visual inspection (Figure 9). Subsequently, the test area was analyzed by means of UV photography, 3D microscopy and Reflection FT-IR spectroscopy [23]. Reflection FT-IR spectroscopy measurements on the painting surface before cleaning showed the characteristic bands of ketone resin, areas K01 and K02 (1710, 1450, 1025 and 945 cm\({}^{-1}\), [23]), that are not present in the spectra acquired on the surface after removal treatment, areas K03 and K04, confirming the effectiveness of the treatment. In these latter areas, the analysis identified the presence of a lipid substance used as a paint binder (Figure 10).