## 4 Conclusions  
MA-XRF analysis carried out on the _Poldi Pezzoli Madonna_ by [PERSON] has proved to be of utmost importance for the conservation interventions carried out at the Opificio delle Piretre Dure in Florence. Indeed, it allowed the evaluation of the integrity of [PERSON]'s original pictorial layer, identifying the original azurite layer below the extended retouching painted with Prussian blue and lead white. These results have thus proved to be a fundamental element for proceeding with the removal of this extended intervention by the painter/restorer [PERSON]. Carrying out MA-XRF analysis also after the conservation intervention was also useful for OPD conservators to evaluate the effectiveness of the process itself. Indeed, one of the greatest advantages of MA-XRF lies in the fact that it yields images rather than just X-ray spectra, which need expertise to be correctly analysed and interpreted. An image instead is just immediate to read and can give strong information even to those professionals who have not undergone specific professional training for scientific data analysis. It is also important to note that the removal of such an extended retouching, as was performed in this case, is of course of considerable interest for art historians: indeed, unveiling the original pictorial layers allows the correct \begin{table}
\begin{tabular}{c c c} \hline
**Colour** & **Elements Detected** & **Hypothesised Pigments/Colourants** \\ \hline White & Pb & Lead white \\ Blue & Cu & Azurite \\ Fe & Prussian blue (Molteni’s) \\ Green & Cu, [Zn] & Malachite 1 \\ Red & Pb & Lead white (+organic dye?) \\  & & Lead white \\ Flesh tone & Pb, Fe, Hg & Fe-based material (earth/ochres) \\  & & Vermilion/cinnabar \\ Background & Ca, Fe & Bone black? \\  & & Fe-based material (earth/ochres) \\ \hline \end{tabular} \({}^{1}\)Zn traces are common in malachite minerals.  
\end{table} 
Table 1: Summary of the results. Elements reported in brackets are intended as traces. Figure 5: The _Madonna Poldi Pezzoli_ before and after restoration: (**a,b**) Fe K\(\alpha\); (**c,d**), Pb L\(\alpha\); (**e,f**) Hg L\(\alpha\); (**g,h**) Cu K\(\alpha\). White is associated with maximum counts and black with minimum ones. and thorough visualisation of the artist's characteristic painting technique and thus the correct evaluation of his style, and even the possibility to conduct a more precise dating of the work of art. After conservation treatments, MA-XRF was carried out also to investigate the original materials and techniques employed by [PERSON]. In this painting, the artist made use of an uncommon painting technique, called distemper, in which the painting layer, making the use of animal glue or vegetable gum, is applied directly onto the canvas with no preparation layer. No varnish was employed with this kind of technique, with the specific aim being to create a matte appearance for the painted surface. The original pigments hypothesised by MA-XRF are consistent with those expected in a painting completed during the late XV century: lead white, azurite, malachite, vermilion, earth/ochres and possibly red organic dye were most likely employed in this painting. Conceptualisation, A.M., L.C. and C.R. ; methodology, F.T. and L.G. ; software, F.T. and L.C. ; validation, F.T. and L.G. ; formal analysis, A.M., L.C. and L.S. ; investigation, A.M., L.C. and L.S. ; resources, F.T., L.G. and F.G.; data curation, F.T. and L.C. ; writing--original draft preparation, A.M. and L.S. ; writing--review and editing, A.M., L.S., C.R., L.G. and L.C. ; visualisation, A.M., C.R., L.C. and F.G.; supervision, F.T. and L.G. ; project administration, F.T. ; funding acquisition, F.T. and L.G. All authors have read and agreed to the published version of the manuscript. This research received no external funding. Not applicable. The authors are grateful to the Opificio delle Pietre Dure and the Poldi Pezzoli Museum for allowing this study. In particular, [PERSON], [PERSON], [PERSON], [PERSON] (OPD), [PERSON] and [PERSON] (Poldi Pezzoli) are gratefully acknowledged.