Scanning macro-XRF (MA-XRF) is a variant of XRF imaging that allows visualization of the distribution of elements in a flat, macroscopic sample (up to several square meters) in a nondestructive manner. This is achieved by scanning the surface of the sample with a focused or collimated X-ray beam of (sub)mm dimensions and analyzing the emitted fluorescence radiation. Due to the penetrative nature of X-rays, elements present at and below the surface contribute to the obtained elemental distribution images. The method is highly valuable in the investigation of historical paintings, as elemental distribution images can reveal hidden sub-surface layers, including modifcations made by the artist or restorations on the surface. In this way it can provide a unique insight into the creative process of the artist(s) and the painting's conservation history.
Ma-XRF scanning experiments at the Van Gogh museum, Amsterdam