Towards the study of alteration patinas on the marble surface of a Renaissance sculptural group from the Museum of Ancient Art (Castello Sforzesco, Milan)

Aim of the present research is the characterization of the alteration patinas present on the surface of a marble Piety dating to Renaissance period and stored at the Castello Sforzesco of Milan. During the last century, a treatment was applied on the statue bringing to the formation of a dark patina which had to be removed. At this purpose, a multianalytical approach, based on both portable noninvasive (XRF and colourimetric measurements) and micro-invasive techniques (FTIR/ATR and SEMEDS), has been applied in order to make available to restorers useful information that allow them to adopt a suitable procedure for the removal of the patina and to recover the statue original appearance.