Identification of forgeries in historical enamels by combining the non-destructive scanning XRF imaging and alpha-PIXE portable techniques

Abstract Particle induced X-ray emission performed with alpha particles (alpha-PIXE) and scanning X-ray fluorescence (XRF) imaging have been used for the non-invasive investigation of three enameled artworks dated back to the XI–XII century AD. The attribution of the three objects has been performed based on art historical considerations even if an analytical investigation was never applied to confirm their authenticity. The alpha-PIXE technique allowed to determine the compositional pattern of the glass matrix in the three artworks; the XRF imaging performed by scanning the sample surface allowed to obtain the signature of opacifying and coloring agents. The high concentration values of Pb in the glass matrix as well as the extensive use of chemical components based on Cr, Zn, and As, questioned the authenticity of the three artworks and postponed their manufacturing dating from the XVIII century AD. The application of a matrix factorization analysis to the XRF data allowed highlighting the chemical associations among Cd, Se, Ba and Zn, indicating the use of a modern cadmium lithopone in the red decorations. The analytical results obtained during the investigation suggest a classification of the three objects as modern copies.