## 4 Discussion  
Table 4 provides a summary of all the identified elements/compounds responsible for the colours for each analytical technique employed and for each sample, together with the proposed identification of the palette. The components belonging to the substrate, i.e., calcite and silicates, are not included. On the basis of the results obtained, it can be stated that the palette employed for the decorations involved the use of numerous pigments and sometimes a simultaneous application of them, indicating a certain level of skill of the artists. In particular, the presence of pigments such as cinnabar, far more precious than red ochre, and the use of gold leaf, could indicate an important commission. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Sample** & **SEM-EDS** & **ATR-FTIR** & **Raman** & **Pigments** \\ \hline
**1** & Hg + S + Fe + Au & red ochre & cinnabar & cinnabar + gold leaf \\  & & & & + red ochre \\
**2** & Fe + Pb & red ochre & red ochre + litharge & red ochre + litharge \\  & & & + cinnabar & + cinnabar \\
**3** & Hg + S + Fe & red ochre & cinnabar & cinnabar + red ochre \\
**4** & Fe & haematite & haematite & haematite \\
**5** & Fe & red + yellow ochre & red ochre + massicot & red ochre + massicot \\  & & & & + yellow ochre \\
**6** & Fe & yellow ochre & yellow ochre & yellow ochre \\
**7** & Fe & celadonite & - & green earth \\
**8** & Cu & Egyptian blue & - & Egyptian blue \\
**9** & Cu & Egyptian blue & - & Egyptian blue \\
**10** & Cu & - & - & Egyptian blue \\
**11** & Ca & calcite & calcite + yellow ochre & calcite + yellow ochre \\
**12** & - & - & amorphous carbon & carbon black \\ \hline \hline \end{tabular}
\end{table} 
Table 4: The main results obtained by means of the different instrumental techniques. Figure 11: EDS spectrum acquired on sample 1 and the corresponding SEM image. Former analyses of cinnabar fresco fragments have already demonstrated that this pigment was often applied upon an aragonite or yellow ochre coat [47], and on a red ochre layer [48], as detected in this study. The absence of organic binders is another important feature of the samples that strongly hints towards the employment of the fresco technique [49]. The fact that calcite is mixed with all the identified pigments is further evidence of fresco technique employment. Thanks to the synergic use of both a portable Raman spectrophotometer and a conventional instrument, a bench tool, it was possible to characterise the entire colour palette. The use of the portable facility might also allow us, in the future, to perform chemical analysis in a non-destructive way, i.e., without the necessity of withdrawing some samples. This study showed that Raman spectroscopy is an extremely effective technique in pigment identification. The two instruments clearly have different characteristics and performances. In particular, we underline that the spatial resolution obtainable with a portable instrument equipped with a fibre optic probe is not equivalent to that of a micro-Raman spectrometer. In fact, the use of the microscope makes it possible both to observe in detail and to focus the laser source on single grains, as observed, for example, in the case of sample 2. However, the portable instrument has the great advantage of being able to carry out the analyses in a completely non-destructive manner, and therefore to be potentially usable in situ, i.e., directly on painted surfaces. From this point of view, another important tool that could be successfully applied thanks to its great versatility and the low cost of the instrumentation, is represented by the colourimetric investigation. The measurements presented in this study have concerned only red and yellow samples and only the visible reflectance results were investigated, but since the technique seems promising, the investigation might be extended to other fragments; it must be also said that this technique can hardly be as effective as FTIR and Raman spectroscopies in identifying mixtures.