## 3 Results
### Spectrocolorimetric Analysis  
To evaluate the cleaning effectiveness, spectrocolorimetric analyses were carried out before and after the cleaning test to determine whether the color of the surface had returned to the color measured before cleaning. Figure 6 reports the total chromatic variation (\(\Delta\)E). The areas represent zones that are cleaned, partially cleaned, or marked by varnish residues; consequently, the standard deviation associated to the measurements is high and thus not reported.  
For the canvases coated with acrylic layers (Table 8) and treated with microcrystalline wax, Gel 3 demonstrated the most effective removal of the coating, while Gel 9 showed no efficacy. Visible residues were observed with Gel 5, Gel 1, Gel 6, and Gel 2, whereas Gel 8 and Gel 7 exhibited partial residue removal.  
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\begin{table}
\begin{tabular}{c c c c c} \hline  & \multicolumn{3}{c}{**Acrylic Painting**} \\ \hline  & \multicolumn{2}{c}{Microcrystalline wax} & \multicolumn{2}{c}{Regalrez 1094 varnish} \\ \hline  & Vis & UV & Vis & UV \\ \hline  & & & & \\ Gel 1 & & & & \\ Gel 2 & & & & \\ Gel 3  
The data highlight that for all cleaning systems used, the colour values of the cleaned surface and the painted surface differ. This difference is significant for canvases painted with acrylic; for oil-painted canvases, however, some cleaning systems achieve \(\Delta\)E values < 5, making the differences imperceptible to the human eye [36].  
For the acrylic-painted and wax-finished canvas, the area treated with Gel 3 presents the greatest disparity relative to the coated canvas and the smallest difference compared to the canvas surface covered only with the acrylic paint layer.  
The ratio between the \(\Delta\)E, representing the difference between the dirty surface and the surface of canvas with only the acrylic varnish on \(\Delta\)E of the surface cleaned with Gel 3 of the acrylic-painted canvas coated with microcrystalline wax, is 0.4. Below is this ratio calculated for other gels:  
Figure 6: Histograms showing the results of total colour variation calculation.  
\begin{table}
\begin{tabular}{c  
Gel 3 (v = 0.4) > Gel 4 (v = 0.7) < Gel 1 = Gel 2 (v = 1.1) < Gel 6 (v = 1.2) < Gel 8 (v = 1.8) < Gel 5 (v = 2.1) = Gel 7 (v = 2.3) < Gel 9 (v = 4.6).  
The lower this ratio, the more the surface appearance is akin to that of the original painted canvas. The most effective cleaning treatments were executed using Methyl Stearate and Methyl Palmitate FAME, which provided superior results compared to ligroin gel.  
Upon examining the oil-painted canvas (also coated with microcrystalline wax) and analysing the data through the same ratio, the following order can be defined: Gel 1 = Gel 3 = Gel 4 (v = 0.4) < Gel 2 (v = 0.6) < Gel 5 = Gel 6 (v = 0.7) < Gel 7 (v = 1.1) < Gel 8 (v = 1.3) < Gel 9 (v = 5.3). These data facilitate the superior cleaning capability of all the experimental systems for the oil-painted canvas relative to the same treatment performed on the acrylic-painted canvas. Considering the results obtained in the cleaning of the Regalrez 1094 varnish covering the acrylic paint layer, the relationship between the chromatic variations of the cleaned area with respect to the painted canvas and the chromatic variations relative to the varnish layer defines the following cleaning order: Gel 3 = Gel 5 = Gel 6 = Gel 7 = Gel 8 (0.2 < v < 0.5) < Gel 2 = Gel 4 (v = 1.1) < Gel 1 (v = 3.1) < Gel 9 (v = 16.6).  
A greater cleaning effect of the various FAME tested was observed following application of the Regalrez 1094 varnish over the oil paint layer. All the tested Gels present a v ratio < 0.3, apart from Gel 6 and Gel 9.