The aim of this work was to identify the materials used for the colours and the metallic parts of a polychrome wooden altarpiece from the 16th century. Since restoration work on the object was almost completed, no sampling was allowed and the analysis had to be performed in a fully non‐destructive manner. Micro‐Raman spectrometry was employed to identify the pigments and the ground layer. Taking advantage of micro‐cracks, it was possible to show that the ground layer was made of calcite and the blue decorations were made of an azurite layer on top of a carbon black underlayer. Lead white was employed for the white areas and for the carnation. Elemental analysis directly performed in air by PIXE with the external nuclear microprobe of the AGLAE accelerator confirmed the results obtained by Raman spectrometry for the pigments and the preparation. It allows the determination of the composition and thickness of the metallic foils and the nature of the underlying support (bolus), two cases where Raman spectrometry is inefficient. The two techniques proved to be fully complementary for the characterization of the materials used for the decoration of this precious altarpiece. Raman spectrometry permits the identification of all pigments including those containing carbon (soot, azurite or lead white), not accessible to PIXE.
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Pagès‐Camagna et al. (2004) studied this question.