## 2 Materials and Methods  
The adopted protocol is based on a two-step survey. In the first part, non-destructive analyses were mainly performed in order to characterise the materials responsible for the colour of the tiles (Table 1) and to address the possibilities of micro-sampling. Micro-fragments (Figure 2 and Table 2) were collected to characterize the composition and the executive technique of gilding, glazes and terracotta bodies. The description of the areas analysed by fibre optic reflectance spectroscopy (FORS), X-ray fluorescence (XRF) and documented by portable microscope are listed in Table 1. \begin{table}
\begin{tabular}{c c} \hline
**Sample’s Name** & **Sample’s Name** \\ \hline SX7\_yellowdark1 & SX4\_white2 \\ SX7\_yellowlight1 & SX4\_white1 \\ SX6\_purple2 & SX1\_white1 \\ SX6\_purple1 & SX1\_lightblue1 \\ SX6\_graydark & BA3\_olive1 \\ SX6\_graylight & BA1\_blue1 \\ SX6\_yellow1 & SX6\_gilding6 \\ SX5\_greenmedium tone1 & SX6\_gilding5 \\ SX5\_yellow2 & SX6\_gilding4 \\ SX5\_yellow1 & SX5\_gilding3 \\ SX4\_greendark1 & SX5\_gilding2 \\ SX4\_greenmedium tone1 & SX5\_gilding1 \\ SX4\_greenlight1 & DX6\_gilding10 \\ SX4\_blue2 & DX5\_gilding9 \\ SX4\_blue1 & DX5\_gilding8 \\ SX4\_white3 & DX4\_gilding7 \\ \hline \end{tabular}
\end{table} 
Table 1: Areas analysed non-invasively by FORS and XRF and documented by portable microscope. Figure 2: Location of the sampling areas and indication of the labels of the tile (AL, DX, BA, SX). \begin{table}
\begin{tabular}{c c c} \hline \hline
**Sample’s Name** & **Sampling Description** & **Analytical Techniques Applied** \\ \hline F\_01 & Tile BA5. On an area with gilded glaze & OM, CS, SEM-EDS \\ F\_02 & Between DX4 and DX5. On the gilding. & OM, CS, SEM-EDS, XRPD \\ F\_03 & Tile DX6. Terracotta body & XRPD \\ F\_04 & Tile DX6 stucco sample & XRPD \\ F\_05 & Between SX6 and SX7 on the tile with darkened gilding & OM, CS, SEM-EDS, XRPD \\ F\_06 & Tile BA1. On the blue decoration where there are high & OM, CS, SEM-EDS \\  & copper signals. Stucco is also present & OM \\ F\_07 & Brown adhesive on the back of a gilded tile. & OM \\ F\_08 & Powder from stucco & XRPD \\ F\_09 & Concrete & XRPD \\ F\_10 & Tile SXS. Pinkish stucco around the blue flower & XRPD \\ F\_11 & Fragment of terracotta and white plaster underneath & XRPD, LA-ICP-MS, firing temperature \\ F\_12 & Fragment of gilded terracotta tile & OM, CS, XRPD, SEM-EDS \\ F\_13 a & Tile BA5. Fragment of terracotta & XRPD, LA-ICP-MS, firing temperature \\ F\_13 b & Tile BA5. Fragment of terracotta & XRPD, LA-ICP-MS, firing temperature \\ \hline \hline \end{tabular}  
* 1 OM: Optical microscopy; CS: cross-section; SEM-EDS: electron microscope energy dispersive X-ray spectroscopy; XRPD: X-ray powder diffraction; ICP-MS: laser ablation-inductively-coupled Plasma mass spectrometry.  
\end{table} 
Table 2: Samples in the present study with the sample name, the numbering and the location on the Monument as shown in Figure 2 and the analytical techniques applied 1.  
certified standard, 99% reflective material) was used. The acquired reflectance spectra were compared with reference spectra included in both ISPC-CNR spectral database (not published) and IFAC-CNR FORS spectral databases of pigments [23]. X-ray fluorescence (XRF) is a powerful technique for acquiring information about elemental composition of glazed terracotta [9; 24; 25; 26]. XRF spectra were collected by a handheld Tracer III SD Bruker spectrometer, equipped with a rhodium anode and solid-state silicon detector with an energy dispersive detection system. The used set-up was: 40 kV acceleration, 12 uA anode current and an acquisition time of 120 s. The measuring area was an elliptical spot of 4 \(\times\) 7 mm. For data treatment the ARTAX software was used after normalizing spectra to the intensity of Rh K\(\alpha\) line at 20.21 keV.