Macro X-ray fluorescence and VNIR hyperspectral imaging in the investigation of two panels by Marco d'Oggiono

Two panels by Marco d'Oggiono - a painter who was active at the end of the 15 century in Leonardo's workshop in Milan - were investigated by Macro X-ray fluorescence spectroscopy and VNIR hyperspectral imaging. The paintings depict St. Francis and St. Anthony of Padua, each presenting a devotee, and are part of the permanent collection of the Pinacoteca di Brera in Milan. They are two of the five still known compartments of the Maleo polyptich, which originally consisted of ten panels. Preliminarily analyses suggested the presence of ancient over-paintings that modified the arrangement of the hair of one devotee and partially changed the dress of the other one. The paper reports the results obtained by investigating the repainted areas by a new mobile apparatus for MA-XRF and by an innovative compact VNIR hyperspectral camera. The aim is to obtain information on the materials and - possibly - on the original appearance of the modified representations. The two instrumental approaches produced images related to the different superimposed painting layers, which supported the interpretation of the subsequent phases of the production of the paintings and highlighted the evolution of the appearance of the subjects.