## 3 Results
See Table 1 for an explanation of the pigment identification codes (ID). between FR-F and FR-SB was 0.81 CIELAB units, therefore, an unnoticeable difference according to [60]. This means that the use of NE by itself did not lead to a difference in colour when applied to the lime-based _intonaco_[60]. On the other hand, \(\Delta\text{E}^{\ast}_{\text{ab}}\) was also calculated between the raw pigment and F paints, and between the raw pigment and SB inpaintings. The results are included in Figure 2, where it can be seen that the \(\Delta\text{E}^{\ast}_{\text{ab}}\) between the raw pigment and SB mock-ups was below 5 CIELAB units in all the paints, a value above which two different colours would be observed [60]. Among all, LA-B-SB was the paint with the highest variation (\(\Delta\text{E}^{\ast}_{\text{ab}}\): 4.93) and, in general terms, synthetic pigments (UL-B, MAR-R, CHR-G, and VER-R) showed values below 2 CIELAB units when used in SB paintings. Regarding the \(\Delta\text{E}^{\ast}_{\text{ab}}\) between the raw pigments and the F paints, the values were generally well above 5 CIELAB units, except for CHR-G-F and CIN-R-F, as expected. In the fresco technique, the pigments are immersed in a calcium carbonate matrix, which makes the colour much less intense, as opposed to SB paints where pigments are mixed with a transparent dispersion (NE). Of the various colour parameters measured (Table 3), the SB mock-ups showed lower L\({}^{\ast}\) than their F counterparts and higher C\({}^{\ast}_{\text{ab}}\). Among other physical properties, the gloss (G) for the F and SB mock-ups was evaluated, represented in Figure 3a. The differences between FR-F and FR-SB were particularly high (  
and SB mock-ups showed similar Ra values. The only SB mock-ups that showed higher roughness than their F equivalents were LA-B, GE-G, and MAR-R. Moreover, the degree of adhesion of the paint layer was evaluated by a peeling test (Figure 3c). The results showed that in both situations (F and SB), the tape peeled off almost all the paint layers, indicating that the degree of adhesion was very low. Still, larger amounts (in mg) of paint were extracted from the F mock-ups. Lastly, static contact angle (\(\theta^{\circ}\)) results are shown in Figure 3d. When the \(\theta^{\circ}\) is below 90\({}^{\circ}\), the surface is considered hydrophilic (as opposed to hydrophobic, i.e., water-repellent) [61, 62]. In this regard, both the F and SB mock-ups had values below 90\({}^{\circ}\) and were, therefore, hydrophilic. The mineralogical characterisation of the paint mock-ups by XRD, regardless of the paint (F or SB), remained in line with the earlier characterisation of the raw pigments (Table 1) with the difference that calcite (CaCO\({}_{3}\)) appeared in all the paintings: in F due to the painting technique itself, and in the SB mock-ups due to the underlying lime-based mortar. The only painting that showed differences in mineralogical composition was VER-G-F. Verdigris pigment corresponds chemically and structurally with the mineral hoganite (Cu(CH\({}_{3}\)COO)\({}_{2}\cdot\)H\({}_{2}\)O), as detected by XRD (Table 1). This phase disappeared in the fresco paint and other compounds were identified instead: a mixed calcium and copper acetate  
Figure 3: (**a**) Average gloss (G, G units) values for all the mock-ups with their standard deviations; (**b**) average roughness (Ra, μm) values for all the mock-ups with their standard deviations; (**c**) average weight in mg of peeled-off material from all the mock-ups with their standard deviations; and (**d**) static contact angle (\(\theta^{\circ}\)) values for all the mock-ups with their standard deviations. Dark grey bars represent F paints and light grey bars SB paints. See Table 1 for an explanation of the pigment identification codes (ID). known as paceite (CaCu(CH\({}_{3}\)COO)\({}_{4}\)-6(H\({}_{2}\)O)) and a hydrated copper silicate known as apachite (Cu\({}_{9}\)Si\({}_{10}\)O\({}_{29}\)-11(H\({}_{2}\)O)).