In parallel with the discovery of lost artistic practices, a large number of works aim at understanding the evolution of these materials with time. Most of the alteration processes, e.g. metal corrosion, involve modification of the redox states of the original material, while the average elemental composition of the bulk material remains unchanged. The alteration processes are usually limited to a highly superficial area,  with typical thickness in the micrometer or even sub micrometer range. Nevertheless, such surface changes can have effects on the objects visual appearance. Probing the oxidation of specific elements and more generally their chemical environments is therefore highly relevant when studying alteration mechanisms. This field is intensively studied at ID21. Indeed, the accessible energy range (2.0–9.2 keV) allows the study of: (i) 3d transition metals, being in pigments, glasses, inks or metals as well; (ii), Cl and S species (e.g. SO2), which are common exogenous species responsible for degradation and corrosion. In parallel, some experiments focus on modern organic based artistic materials, for which the use of µFTIR microscope provides valuable information.