## 2 Materials and Methods
### Efficacy of Cleaning Test  
To define the effectiveness to remove the varnish and microcrystalline wax, targeted analytical methods were employed:  
* UV-vis imaging was conducted to macroscopically assess the efficacy of cleaning using various FAME. Visible and UV light imaging was employed to capture crucial data regarding surface layer conditions and the extent of varnish removal. Imaging was performed on the canvas using a CANON EOS M50, Canon, Tokyo, Japan full spectrum camera equipped with specific filters: the HOYA UV-IR (Madatec, Milan, Italy) cut filter 52 and Yellow 495 52 mm F-PRO MRC 022(Madatec, Milan, Italy) even though the camera was positioned as parallel as possible to the surface some reflection of the varnish can still be seen. For each FAME, the removal area ratio was calculated by processing acquired images: the percentage of the residues area (in black) to the entire sample area of the cleaning test. The percentage of the black area was determined used Photoshop Adobe (v.CS6) software to identify the pixels with the different colour in the picture, using a tolerance of 5% (Figure 2). The image was rasterized at 600 DPI and subsequently, its histogram was analysed using Photoshop. The obtained value was divided by 255 and then subtracted from 1. This process allowed for obtaining the percentage of black normalized to 1 (where 1 represents 100% black and 0 represents 0% black). Additionally, the values of clean areas were normalized based on the values obtained from the same areas in the untreated canvas, as shown below. * A DinoLite AM411-FVW digital microscope (Leica Microsystems, Wetzlar, Germany) operating at 40 and 220 magnifications in both visible (VIS) and ultraviolet (UV) light modes was used to observe surface morphology. * Spectrocolorimetry was conducted using the YS3010 3 nh Handheld Spectrophotometer (Shenzhen ThreeNH Technology Co., Ltd, Shenzhen, China) to define the colour surface difference before and after the cleaning treatments, using the total colour variation (\(\Delta\)E) as a quantitative index to evaluate cleanliness. \(\Delta\)E was calculated as the difference between the colour parameters of the surfaces following cleaning treatment and those of the surfaces both without the application of crystalline wax and Regarlez  
Figure 1: Placement of the FAME gels on the prepared laboratory samples. 1094 varnish and with the application of the two coatings. To facilitate the analysis of colorimetric data, emphasis has been placed on calculating chromatic variation concerning the surface obtained after the cleaning treatment in comparison with the painted surface and the surface coated with Regarlez or microcrystalline wax. For this purpose, the following index has been computed:  
\(\
u=\Delta\)E (Surface after the cleaning Treatment \(-\) Painting surface)/  
\(\Delta\)E (Surface Surface after the cleaning Treatment \(-\) Surface with the wax/Regarlez coating)  
Colorimetric data were collected from the same regions of the painted canvas, treated with both types of varnish, and cleansed (five areas divided into a central zone and four corners). The data represent an average of measurements collected from the following areas. * To confirm the absence or presence of surface residues, Fourier-transform infrared (FTIR) spectroscopy in attenuated total reflection (ATR) mode was performed using the Nicolet Summit Pro instrument from Thermo Scientific (Waltham, MA, USA). The areas that appeared macroscopically clean were brought into contact with the instrument's diamond. Spectra were acquired in the range of 400-3200 cm\({}^{-1}\), with a total of 32 scans at a resolution of 4 cm\({}^{-1}\);
* Scanning electron microscopy (Tescan Vega model) was performed to better understand the interaction between the non-polar coating and the underlying pictorial layer.