Stratigraphy of a layered structure utilizing XRF and scattered photons

A novel non-destructive method named Beam Edge Stratigraphy has been developed. This method targets the inspection of a layered structure deposited onto a massive substrate. The investigated object is irradiated by a planar, sharp X-ray beam passing over the surface at an acute angle. The scattered and XRF photons are recorded by a pinhole camera equipped with a semiconductor pixelated detector. Overall information about the layered structure is obtained for the area where this structure is fully enclosed within the planar beam, while measurement of the layer thicknesses with micrometric precision is obtained by analysing changes in the signal produced at the sharp edge of the beam. The technique presented primarily targets the investigation of medieval wooden panel paintings based on polychromy. Polychromy consists of several thin layers in a variety of colours and elemental composition. It is highly desirable to non-destructively investigate the current status of existing polychromy for various reasons, such as detecting possible deterioration and identifying previous restoration activities.