# Multi-Analytical Investigation on a Renaissance Polychrome
## 4 Discussion
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Sample**} & \multirow{2}{*}{**Layer**} & \multirow{2}{*}{**Colour**} & \multicolumn{2}{c}{**SEM-EDS**} & \multirow{2}{*}{**ATR-FTIR**} & \multirow{2}{*}{**Composition**} \\  & & & **(Characterising** & & **(Peaks, cm\({}^{-1}\))** & \\  & & & **Elements)** & & \\ \hline \multirow{8}{*}{1} & A & white/grey & Ca, Si & 2930, 2860, 1650, 1550, \(-\)1400 (br), & calcite, silicate, proteinaceous \\  & B & white & Pb & \(\sim\)1000 (br), 873 & compound \\  & C & white/grey & Ca, Si & \(\sim\)1400 (br), \(\sim\)1000 (br), 873 & calcite, silicate \\  & D & whitish & Ba & 1180, 1120 (sh), 1085, 985 & barite \\  & E & white/grey & Ca, Si & 2930, 2860, 1650, 1550 & calcite, proteinaceous \\  & F & white & Pb & 3435, 1400, 1045, 770 & biacca \\ \hline \multirow{8}{*}{2} & A & white/grey & Ca, Ba, S & 1410, 1180, 1110, 1060 & Calcite, barite \\  & B & white & Pb & 2930, 2860, 1650, 1550, 1400 & biacca and \\  & C & blue & Fe, Co, & 2080 (PB), 1060, 790 & proteinaceous material \\  & D & blue & Cu & 3420, 1465, 1090, 1026, 1400, 950, 820 & Azurite \\ \hline \multirow{8}{*}{3} & \multirow{2}{*}{-} & \multirow{2}{*}{blue} & \multirow{2}{*}{Cu, Ba, S} & 3425, 1492, 1463, 1412, 952, 833, 815, & Azurite, \\  & & & & 770, 740, 490, 446 & Barite \\  & & & & 1185, 1080, 635, 603 & \\ \hline \multirow{8}{*}{4} & \multirow{2}{*}{-} & dark & \multirow{2}{*}{Fe, Si, K, Al, Pb, Ca} & 1393 (br), 678 & \\  & & & 2920, 2849, 1651, 1550 & & \\  & yellow & Fe, Si, K, Al, Pb, Ca & 1318, 1083, 1032, 913, 798, 779, 530, & \\  & & & 470, 3325, 3400, 1460, 667, 598,874, 713 & & \\ \hline \multirow{8}{*}{5} & \multirow{2}{*}{-} & gold & Au, Si, Al, Pb, Ca, S, Ba & 1400, 874,713 & Gold, Lead white, Calcite, \\  & & & Ba & 1185, 1080, 635, 603 (ba), 1088, 1032, & Barite, silicate \\  & & & 913, 798, 779, 1393 (br), 678 (lw) & & \\ \hline \multirow{8}{*}{6} & A & red & Hg, Pb, Ba, S & 2925, 2860, 1715, 1390, 1180, 1060, & Cinnabar, lead white, barite, \\  & B & white/grey & Ca & 1400, 678 & organic material \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Summary of the results obtained and composition of the samples. synthetic origin, due to later interventions in the artwork. In particular, barite appeared spread all over the artwork, denoting a wide intervention between the end of the 18 th and the beginning of the 19 th century. In more detail, the original white pigment was probably white basic lead carbonate. This hypothesis was suggested by its presence in the layer that was closer to the terracotta's surface in white sample 1. As barium sulphate (barite) started to be employed as a pigment and as an extender around the end of the 18 th century, the presence of consecutive layers of barite indicates previous restoration work. Particularly for lead white, in the early 19 th century [69], when its use became more common because of the availability of synthetic pigment [25]. With regard to sample 2, in this case, the stratigraphy clearly indicates that the blue layer was restored as well. Indeed, the coating layer contained barite together with calcite and glue, and the immediately underlying layer was Prussian blue, whose use in artwork began after 1704 [70]. Therefore, the latter pigment does not have to be considered part of the original painting. The presence of smallino could instead be considered controversial. It is an inorganic pigment, a potassium and cobalt double silicate with metal oxides, which has been used in painting since the Renaissance [24]. However, since the layer with the smallino also contained Prussian blue, it was assumed to be the result of the same restoration and not part of the original painting as well. It seems possible that the mixture of Prussian blue with smallino was made to better imitate the colour of the original pigment, i.e., azurite. Ultimately, sample 2 shows how the lowest layer, i.e., the oldest one, was made with one of the most precious pigments, which was also established in the workshop of [PERSON]: azurite.