## 3 Results
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Pigment ID** & **Bond/Group Type** & **Wavenumber (cm\({}^{-1}\)) and** & **Assignment** \\  & **and Vibration** & **Relative Intensity \({}^{\ast}\)** & **Assignment** \\ \hline  & Si-O antisymmetrical stretching & 1230 (w), 1159 (m), 1050 (vs), 997 (vs) & Cuprorivaite [37, 38] \\  & Si–O symmetrical stretching & \(\approx\)800 (vw) & Quartz [36, 39] \\  & Si–O symmetrical stretching & 755 (w), 662 (s) & Cuprorivaite [37, 38] \\ EG-B & Si-O antisymmetrical bending & \(\approx\)518 (m) & Quartz [36, 39] \\  & Si-O bending & 480 (vs) & Cuprorivaite [37, 38] \\  & Si,Al–O & \(\approx\)420 (vs) & Feldspars [40] \\ \hline  & -OH stretching & 3580–3000 (b) & Muscovite (?) \\  & Si,Al–O & 1430 (vw), 709 (w), 620 (sh) & Lazurite [41, 42] \\ LA-B & Si,Al–O stretching & \(\approx\)965 (vs) & Sodalite [36, 43, 44] \\  & CO\({}_{3}\)\({}^{2-}\) antisymmetrical bending & \(\approx\)875 (sh) & Calcite [36, 45] \\  & Al–O–Si in-plane vibration & \(\approx\)750 (vw) & Muscovite [46] \\  & -SO\({}_{4}\)\({}^{2-}\) & 665 (m) & Lazurite [42] \\ \hline  & -OH stretching & 3688 (w), 3621 (w) & Kaolinite [47] \\ UL-B & Si,Al–O stretching & 980 (vs) & Sodalite [43, 44] \\  & -SO\({}_{4}\)\({}^{2-}\) & 665 (m) & Lazurite [42] \\  & Al,Si–O & 797 (vw), 752 (vw), 420 (vs) & Kaolinite [40] \\ \hline  & -OH stretching & 3600–3200 (b) & Phyllosilicates [40, 48, 49] \\ GE-G & Si–O & \(\approx\)1630 (w), 970 (vs) & Glauconite/Celadonite [40, 48, 49] \\  & CO\({}_{3}\)\({}^{2-}\) antisymmetrical bending & 875 (sh) & Calcite [36, 45] \\  & CO\({}_{3}\)\({}^{2-}\) symmetrical bending & 711 (sh) & Calcite [36, 45] \\ \hline  & \multirow{2}{*}{Fe–O stretching} & 535 (m), 510 (s), 465 (m), 425 (s), 385 (w), & \\ MAR-R & Fe–O stretching & 325 (w) & Iron oxide [50, 51, 52] \\ \hline  & \multirow{2}{*}{Cr-O tension} & \(\approx\)607 (s)5, 577 (vw), 497 (sh), 474 (vs), & \\  & & 460 (vs), 450 (vs) & Chromium oxide [53, 54] \\ \hline  & Si–O antisymmetrical stretching & 1210–1030 (br) & Quartz [55] \\ CIN-R & Si–O symmetrical stretching & 750–600 (br) & Quartz [55] \\  & Hg–S tension & 345 (m), 283 (m) & Cinnabar [56] \\ \hline  & Si–O antisymmetrical stretching & 1210–1030 (br) & Quartz [55] \\ VER-R & Si–O symmetrical stretching & 750–600 (br) & Quartz [55] \\  & Hg–S tension & 344 (m), 284 (m) & Cinnabar [56] \\ \hline  & -OH stretching & 3450 (s), 3365 (s), 3270 (s) & Copper acetate [57, 58, 59] \\  & CO\({}^{\circ}\) symmetric stretching & \(\approx\)1594 (vs) & Copper acetate [57, 59, 58, 59] \\ VER-G & CO\({}^{\circ}\) antisymmetric stretching & 1418 (vs) & Copper acetate [57, 58, 59] \\  & C–H related to CH\({}_{3}\) group & 1355 (m), 1049 (m), 1033 (m) & Copper acetate [57, 58, 59] \\  & C=O symmetric stretching & 1260 (vw) & Copper acetate [57, 58, 59] \\  & O–C–O deformation mode & 690 (m), 626 (m) & Copper acetate [57, 58, 59] \\ \hline  & \multicolumn{2}{c}{(\({}^{\ast}\)) relative intensity vs (very strong); s (strong); m (medium); w (weak); vw (very weak); sh (shoulder); br (broad).} \\ \end{tabular}
\end{table} 
Table 2: Molecular composition of the raw pigments by Attenuated Total Reflection Fourier-transform infrared spectroscopy (ATR-FTIR). See Table 1 for an explanation of the pigment identification codes (ID). The colour data for the non-painted mock-ups, the raw pigments, and the F and SB paint mock-ups are presented in Table 3. On the one hand, it was observed that in the unpainted mock-ups, regardless of whether NE was applied or not (FR-SB and FR-F, respectively), the values were very similar to each other. In fact, the colour difference (\(\Delta\)E\({}^{*}_{\text{ab}}\))  
Figure 2: Micrographs of the raw pigment (**left** column), fresco paints (-F, **central** column), and the nano-silica-based reintegrations (-SB, **right** column). The colour difference (\(\Delta\)E\({}^{*}_{\text{ab}}\), in CIELAB units) between the raw pigment and F paints, and between the raw pigment and SB paints is included in each figure.