Inspecting adhesion and cohesion of protectives and consolidants in sandstones of architectural heritage by X-ray microscopy methods

An innovative set-up of synchrotron radiation soft X-ray Fluorescence was applied at the TwinMic beamline (Elettra Sincrotrone Trieste) to test the potential of the method in investigating the interaction between protectives and consolidants with sandstone substrates. To this purpose, products developed in the framework of the EU-funded Nano-Cathedral Project (grant agreement No 646178) were studied through chemical mapping of sandstone cross sections with the aim of inspecting the distribution and the adhesion/cohesion ability of the products. The paper illustrates the obtained results, also in combination with SEM-EDS imaging, paying special attention to the experimental challenges encountered in the use of the TwinMic set-up. Even though the TwinMic microscope normally works in transmission mode to focus the microprobe on the sample, we successfully managed to scan thick (1 mm) samples in reflection mode, thus showing the potential of this technique for the investigation of samples that cannot be easily prepared as thin (≤1 μm) cross sections.