# Multi-Analytical Investigation on a Renaissance Polychrome
## 3 Results  
### Analyses of Microsamples  
#### 3.1.1 White Sample 1  
Sample 1 was taken from the white habit of the Carthusian priest, visible on the left side of the artwork. It was composed of a whitish fragment of about 3 \(\times\) 2 mm and of a little powder of the same colour. The macroscopic visual observation of the sample, particularly the one performed by using the stereo microscope with 3\(\times\) magnification, showed that the sampling also removed part of the underlying substrate, a condition that often occurs at this stage, as we will see in subsequent cases. The size of the sample permitted dividing it; therefore, part of it was embedded and cross-sectioned to highlight and characterise each overlapped layer. The SEM-EDX analyses performed on the sample surface clearly revealed that lead was the main element, whose presence was attributable to the use of lead white, the so-called biacca (2 PbCO\({}_{3}\)Pb(OH)\({}_{2}\)). Moreover, the presence of sulphur and barium were attributed to the possible presence of barium sulphate (also known as barium white or barite), whereas a small amount of calcium was thought to be associated with the presence of calcite (CaCO\({}_{3}\)). All those white substances could have been used as white pigments, even though, as we will also discuss further, it is more likely that biacca was the original material and barium white was added afterwards. Indeed, the latter is a white pigment of artificial origin whose use in artwork dates to the 19 th century [41; 42; 43]. Other elements such as silicon, aluminium, chlorine, bromine, iron, and potassium, also present in the sample, were attributed to the carthenware substrate. Then, ATR-FTIR tests on a small grain of the same sample confirmed some of the results that had already been found. In particular, the analysis brought to light the unequivocal presence of lead white because of the characteristic bands around 1400 cm\({}^{-1}\), 1042 cm\({}^{-1}\), and 678 cm\({}^{-1}\)[44]. The additional bands at 3300 (br), 2920, 2849, 1651, and 1538 cm\({}^{-1}\) were attributed to the presence of a kind of proteinaceous organic substance, especially because amide I and amide II bands were detected [8; 30; 45]. The micro-invasive analyses carried out on the embedded and cross-sectioned white sample 1 provided crucial information on the layering and the distribution of materials. The microscopic observation under visible and UV light highlighted a complex stratigraphy composed of several overlapped pigmented layers, as visible in Figure 2.  
The micro-ATR-FTIR and EDX results confirmed the presence of biacca as the main white pigment in the entire stratigraphy. In particular, the FTIR spectra acquired in correspondence with layers B (Figure 3a) and F revealed the strong absorption band at 1400 cm\({}^{-1}\) together with the characteristic bands at 3435, 1045, and 770 cm\({}^{-1}\)[46]. Additionally, the EDX was performed on several particles dispersed in the same layers and the results revealed high counts of Pb. As for layer D, the ATR-FTIR spectra also suggested the presence of barite because of the bands at 1180, 1085, and 985 cm\({}^{-1}\), and the shoulder at 1120 cm\({}^{-1}\)[25; 47; 48]. The EDX analysis confirmed this hypothesis thanks to the signals of sulphur (S) and barium (Ba) related to barite pigment. In addition, signals of calcium (Ca), were identified in some particles dispersed into layers A, C, and E. This pointed to the presence of calcite and signals of silicon (Si) could indicate the presence of some silicate compounds in layers A and C, which were not clearly revealed by ATR-FTIR. In correspondence to layers A and E, the well-defined bands at 1650 and 1550 cm\({}^{-1}\), together with the typical sharp bands at 2930 and 2860 cm\({}^{-1}\) (Figure 3b), confirm the presence of proteinaceous material. While the proteinaceous material in layer A was likely to be part of the dark coating, the one in layer E could have possibly been used as a binder or adhesive [49]. No traces of oil-based binders were identified.