The X-ray fluorescence spectroscopy (XRF) technique is employed to detect the chemical elements that make up materials by exploiting the interaction between X-rays and the atoms in compounds. In the field of cultural heritage, particularly in the case of polychrome painted surfaces such as paintings on canvas, panel and murals, it is widely used, due to its versatility and non-invasiveness (it does not compromise in any way the integrity of the work under investigation), to identify the chemical elements characteristic of the mineral pigments used by the artist

Indeed, chemical elements defined as “chromophores,” i.e., capable of defining the color of a given compound, can be found in most pigments. For example, mercury (Hg) and sulfur (S) can be detected in a red background painted with a pigment called cinnabar or vermilion (HgS); similarly, lead (Pb) can be found in a white drafting of lead or white lead ((PbCO₃)2·Pb(OH)₂, and so on. The use of this technique makes it possible to preliminarily define the palette used in the creation of a work.