## 3 Results  
### FTIR Analysis  
FTIR spectra registered on all pigmented layers are dominated by the strong absorption bands of calcite (CaCO\({}_{3}\))--characteristic IR absorptions associated with the fundamental vibrations of the carbonate group observed around -1400 cm\({}^{-1}\) (broad peak), 872 cm\({}^{-1}\), and 712 cm\({}^{-1}\)[22]. The small peaks at 2512 and 1795 cm\({}^{-1}\) (combination bands) can also be ascribed to calcite [23]. As indicated by the FTIR data registered on the white painted areas, calcite was also the choice for the white pigment. In some of the registered FTIR spectra (Figure 3a), the presence of an organic material could be clearly inferred via the weak but characteristic bands observed at 2923 and 2854 cm\({}^{-1}\) (aliphatic C-H stretching). For the same samples, the amide I and amide II bands at 1639 and 1588 cm\({}^{-1}\) were also observed, a clear indicator of proteins [24]. Examination of red areas indicated the use of red ochre. As it can be seen in Figure 3a, iron oxides under the form of hematite (Fe\({}_{2}\)O\({}_{3}\)) were identified via the specific absorption bands at 467 and 532 cm\({}^{-1}\). Compared to the literature [25], this last peak, typically around 550 cm\({}^{-1}\), is slightly shifted toward lower wavenumbers, a situation that may be explained by an increase in Al-for-Fe substitution in the hematite structure [26]. The shift towards lower wavenumbers of the hematite IR band could also be due to the particle size and shape (morphology) [27]. Accessory minerals associated with the iron oxide compounds were also identified, such as kaolinite--characteristic bands observed at 3696 and 3621 cm\({}^{-1}\) (outer and inner hydroxyl ion bands), 1028 cm\({}^{-1}\) (Si-O-Si band), and 914 cm\({}^{-1}\) (Al-O-H band). Small amounts of quartz, typically found with kaolinite, were also observed--peaks at 1163, 799, and 781 cm\({}^{-1}\)[25; 28]. The infrared spectrum registered on the yellow finishing layer (Figure 3b) was found to be somehow similar to the one registered on red areas. However, compared to red ochre, the characteristic peaks of ferric oxides are sharper and more intense. A peak at 397 cm\({}^{-1}\), frequently found in ochre or earth-based pigments [29], can also be observed. This band is thought to be due to SiO\({}_{4}\)-SiO\({}_{4}\) coupling in silicate [30], while other studies assign this band to Fe-O bands in yellow ochre [31]. However, no other characteristic bands of either goethite or limonite, commonly found in yellow-based ochres, were observed. Compared to the red pigmented areas, higher amounts of quartz seem to be present, while bands caused by the free hydroxyl ions of kaolinite, in the upper region of the spectra, are missing. Instead, within this region of the spectra, a small peak centered around 3627 cm\({}^{-1}\) is present that may be ascribed to Al-OH vibrations in illites [32]. The broad and intense peak at 1013 cm\({}^{-1}\), with a shoulder band at 914 cm\({}^{-1}\), could be ascribed to kaolinite. This shift  
Figure 3: FTIR spectrum registered on the red (**a**) and yellow (**b**) pigmented areas (samples S2 and S6). The absorptions of the various accessory minerals associated with the natural ochre pigments are marked on the spectra as follows: K—kaolinite; Q—quartz; H—hematic; I—illite. towards lower wavenumbers of the main vibration in kaolinite (normal values are between 1028 and 1036 cm\({}^{-1}\)) could be due to interferences with the 1085 cm\({}^{-1}\) band in quartz as well as the particle size [33]. However, due to the fact that the most characteristic bands for kaolinite in the upper region of the spectra are missing, kaolinite is either not present or present in very small amounts. Based on IR absorptions within the 1270-880 cm\({}^{-1}\) region, a clear identification of the clay minerals present in the analyzed sample is not possible by FTIR analysis alone [34].