**5. Conclusions**

The results obtained show a substantial uniformity in the typology of the pigments used on the east, north, and west walls of Alexander and Roxane's Wedding Room in Villa Farnesina, Rome. Additionally, the execution technique relative to the mixtures of pigments used was found to be the same, in the rendering of yellows and their different shades from colder tones to golden ones, and in the blue hues on a white background. Although it is not known how much time passed between the execution of the two frescoes, it should be noted that the palette of the east and north walls is the same as the third wall, the west one. In particular, those pigments that in the two walls frescoed by Sodoma are a reason of interest because they were still uncommon or because they were available in a limited period of time, such as Naples yellow, caput mortuum, and smalt, are also found, used in the same way, in the third wall. Combining the spectroscopic evidence resulting from the non-invasive analyses of pigments with historical sources, we hypothesized that the decoration of the third wall, which represents the Taming of Bucephalus, was carried out shortly after 1520 and within the sixteenth century, as evidenced by the use of smalt containing Bi impurities. Moreover, the decoration of the third wall was likely accomplished by an artist who surely knew Sodoma's painting technique very well, as evidenced by the same materials used, and the same execution technique for painting particular areas. This work demonstrates how investigations on pictorial materials can reveal very useful details, much like documentary sources, in order to obtain—totally non-invasively—crucial information about some still uncertain artistic productions.

**Author Contributions:** Conceptualization, C.A. and M.V.; methodology, M.V., M.A. and C.A.; investigation, M.V., M.A., C.A. and A.S.; resources, A.S.; data curation, M.V. and C.A.; writing—original draft preparation, C.A. and M.V.; writing—review and editing, M.V., M.A., C.A. and A.S.; supervision, A.S. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research received no external funding.

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Acknowledgments:** Virginia Lapenta is gratefully acknowledged for her kind availability, the interesting case which she invited us to study, and the images supplied.

**Conflicts of Interest:** The authors declare no conflict of interest.
