# Multi-Analytical Investigation on a Renaissance Polychrome
## 3 Results
### Analyses of Microsamples
#### 3.1.2 Blue Sample 2  
Sample 2 was taken from [PERSON]'s mantle, and it was composed of three intense blue micro-fragments (about 5 mm in diameter each). Lead was the most common element in all of the point-like SEM-EDXS analyses. This was again due to the use of lead white. Additionally, copper was found widespread on the surface of the sample. This is probably because of the presence of a blue copper-based pigment that explained the sample's colour as well. The signals of sulphur and calcium suggested the presence of gypsum and calcite, whose use could be related to the preparation of the artefact's surface before applying the paint film. The presence of silicon was instead considered part of the terracotta substrate. It is worth noting that high percentages of iron marked that blue sample. This fact was initially attributed to the earthanware substrate. Then, the elements present on the sample's blue surface were mapped using the other SEM-EDX instrument. Copper and lead were found to be the most common elements and were confirmed to be the main ones. Furthermore, the presence of cobalt was evidenced. This was attributed to cobalt blue, also known as smallino. It is a blue glassy pigment composed of silicon oxide, potassium oxide, and cobalt oxide, whose use started in the Renaissance and whose blue colour is due to the presence of cobalt [24; 50]. Subsequently, the ATR-FTIR analysis was performed on a small portion taken from one of the samples. The main bands of lead white were detected around 1400 cm\({}^{-1}\) and at 680 cm\({}^{-1}\), whereas the characteristic bands of azurite were found placed at 3420, 1400 (overlapping with those of biacca), 1091, 952, 833, 815, 740, and 446 cm\({}^{-1}\)[47; 51]. Only FTIR analysis enabled conclusive confirmation of the presence of the copper-based blue pigment in the sample, as detailed further on. Additionally, the very strong bands at 2080 and 602 cm\({}^{-1}\) allowed the identification of another blue pigment, i.e., Prussian blue (Fe\({}_{4}\)[Fe(CN)\({}_{6}\)]\({}_{3}\)) [52; 53]. The latter result was likely to be correlated to the high percentage of iron detected by SEM-EDXS analysis [54]. The other main band in the spectrum, namely the ones at about 3300 (br), 2920, 2849, 1650, and 1538 cm\({}^{-1}\) could be associated with proteinaceous organic substances, but it was not possible to attribute them to any specific compound. The additional band at 1025 cm\({}^{-1}\) pertains to silicates, and they are possibly due to chrysocolla Cu\({}_{2}\)H\({}_{2}\)Si\({}_{2}\)O\({}_{5}\)(OH)\({}_{4}\cdot\)nH\({}_{2}\)O [46; 47]. Chrysocolla is a blue-green, or at times black, silicate mineral with an exceptional variety of formulae and properties used since antiquity in the soldering of gold, in jewelry, and as a pigment [55; 56]. Its correlation with azurite can be made clear because of the frequent contemporary presence of the two minerals in nature [57]. As for that sample, a multi-layer stratigraphy, composed in this case of four overlapped layers, was observed (Figure 4). The ATR-FTIR analysis performed on the cross-section revealed that in layer A, a mixture of white pigments made of calcium carbonate and barium sulphate was present. They were identified thanks mainly to the absorption bands at around 1410 cm\({}^{-1}\)[58] and 1180, 1110, and 1060 cm\({}^{-1}\)[47; 48] and to the related presence of calcium- and barium-based particles. Some particles mainly composed of titanium (Ti) were also identified in layer A by SEM-EDXS. Moreover, the results of both ATR-FTIR and SEM-EDXS techniques revealed the widespread presence of lead white in layer B, as well as that of organic material that was not clearly identified. About layer C, malt and Prussian blue were recognised by the characteristic FTIR bands (Figure 5a), respectively at 1060 and 790 cm\({}^{-1}\)[59] and 2080 cm\({}^{-1}\)[52; 53].