Clinical CT densitometry for wooden cultural heritage analysis validated by FTIR and Raman spectroscopies

The identification and characterization of wood material represent an ongoing challenge for artefacts of interest in cultural heritage. Fourier transforms infrared spectroscopy (FTIR) and micro-Raman (MRS) spectroscopies and more recently Surface-Enhanced Raman Scattering (SERS), being non-destructive techniques, have been largely used for the analysis of painted wood. In this work, for the first time, the X-ray Computed Tomography (CT), using a CT medical scanner, was adopted to discriminate three types of wood, usually used in the construction of heritage objects. Wood interior features have been identified in CT images processed through the volumetric rendering technique (VRT), without the need to destructively "take out" a piece of the sample. The information at the macroscopic level collected by CT (density, volumes, morphology, etc.) was enriched by the evidence, at the microscopic level, obtained by the Raman and FTIR spectroscopic techniques. So, the samples have been classified in softwood and hardwood, with the advantage with respect to the conventional analytical methods to be able to distinguish specific structures within the cell walls only through the CT diagnostic technique. Ultimately, a new non-destructive approach is proposed to analyze wood-based heritage objects, but which can be also extended to other materials (i.e., pigments, glues, consolidants).