## 1 Introduction  
Analytical methods employed in heritage science for the analysis of materials and production techniques are a well-established research field, demanding high performance, non-invasive, non-destructive and portable instruments [1, 2, 3, 4, 5, 6, 7]. These qualities can be found in the X-Ray Fluorescence (XRF) technique, and for this reason it is one of the most employed analytical methods in heritage science, as indeed it allows relatively fast multi-elemental, non-invasive, non-destructive and in situ analyses [8, 9, 10]. Nowadays, modern instruments upgrade the considerable potentiality of this method by means of scanning equipment, yielding elemental distribution maps of a selected area. This technique is known as Macro X-Ray Fluorescence (MA-XRF) by the scientific community and is widely employed in the heritage science field [11, 12, 13]. It is typically exploited for the study of pigments in paintings [14, 15, 16] but also for archaeological finds [17, 18], glasses [19, 20] and many other applications.  
The study presented here is a typical example of MA-XRF's capabilities as an analytical technique but also as a useful, and even decisive, tool for conservators as preventive analysis. The _Madonna with Child_ by [PERSON], also named the _Madonna Poldi Pezzoli_, underwent conservation and restoration treatments at the Opificio delle Piretre Dure (OPD) in Florence, and one of the main goals of the study was the evaluation of the extent of likely wide retouchings by [PERSON] over [PERSON]'s original pictorial layer. These retouchings, painted during 1863-1865, were surely aimed at preserving and improving the aesthetic quality of the painting but unfortunately changed the pictorial aspect of the original distemper technique. OPD conservators faced then the choice of removing or not the large previous restoration intervention, and to do so, they needed to carefully and objectively evaluate the integrity of the original layer underneath.  
To support this complex restoration intervention, MA-XRF analysis was carried out with the scanner developed by the Cultural Heritage Network of the Italian National Institute of Nuclear Physics (INFN-CHNet). MA-XRF analysis was carried out primarily with the aim of supporting the conservation treatment of the painting. The identification and determination of the extent of the interventions by [PERSON] was the primary goal of the study. It is needless to say that the object of the study was also the characterisation of the original painting materials and techniques employed by [PERSON]. For this reason, the painting was entirely scanned before and after the restoration treatment to better characterise the original materials employed by the artist for such a peculiar painting technique. To our knowledge, only one scientific paper has been published exploiting MA-XRF on a painting by [PERSON], which was written by [PERSON] et al. [21].  
It also has to be noted that performing MA-XRF analysis right after conservation treatment has been useful for OPD conservators to carefully evaluate the overall effectiveness of the thorough removal of [PERSON]'s interventions.  
It is worth underlying here the importance of the holistic approach of combining scientific analytical methods with history of art research, with the aim of supporting long-term preservation and understanding of artworks and tangible heritage in general.