Integration of multispectral imaging, XRF mapping and Raman analysis for noninvasive study of illustrated manuscripts: the case study of fifteenth century “Humay meets the Princess Humayun” Persian masterpiece from Louvre Museum

Abstract

The famous Persian illustrated manuscript's page called "Humay meets the Princess Humayun" from Louvre Museum was investigated using multispectral imaging, X-ray fluorescence mapping and Raman spectroscopy for a deepen study of its constitutive materials and painting techniques and to evaluate the state of conservation of the artwork. Cross image treatments were also performed in order to extract further knowledge from the artwork. Due to the extreme fragile nature of the object and its outstanding value in the collection of Louvre's Department of Decorative Arts, noninvasive and contactless diagnostic methods were chosen. Hypercolorimetric Multispectral Imaging (HMI), a portable 7-band multispectral system and its native digital image processing (DIP) software for image treatment, was used to integrate X-ray fluorescence (XRF) imaging mapping to multispectral and colorimetric dataset. It allowed to study the rich color palette, identify original materials and restoration interventions and eventual degradations of both pictorial layer and ancient paper. Punctual Raman spectroscopy was performed to confirm hypotheses of pigments characterization made on infrared and ultraviolet false color images (IRFC, UVFC). Image treatments crossing multispectral data and analytical punctual techniques investigated possible correlation between datasets providing interesting and easy-to-read distribution maps for chemical elements, which are characteristic for pigment identification. In particular, pigments not detectable through XRF for light-element limit of detection as ultramarine blue (lapis lazuli) and organic dyes were successfully identified and mapped. This integrated approach of multisource imaging data is a valuable tool for restorers and conservators, encouraging new protocols of noninvasive diagnostics for cultural heritage.

Minero‐chemical and provenance analysis of Achaemenian lapis lazuli cylinders from Persepolis

“…As mentioned above, lapis lazuli has been observed as a decorative gemstone on the Iranian Plateau from the third millennium BCE onward, as is observed in Susa, Shahr‐i Sokhta and Tappeh Hissar (e.g., Bulgarelli, 1974; Majidzadeh, 1976, 1982; Tosi, 1989). Furthermore, it was used to produce pigments and glaze colourants during later periods, such as the Islamic era on the Iranian Plateau and surrounding areas (e.g., Colantonio et al, 2021; Colomban, 2003; Couvrat Desvergnes et al, 2021; Koochakzaei et al, 2022). In all cases, Afghanistan has been considered an important supplier of raw lapis lazuli in the ancient world (e.g., Iranian Plateau, Mesopotamia, India, Egypt, etc.)…”

“…As mentioned above, lapis lazuli has been observed as a decorative gemstone on the Iranian Plateau from the third millennium BCE onward, as is observed in Susa, Shahr-i Sokhta and Tappeh Hissar (e.g., Bulgarelli, 1974;Majidzadeh, 1976Majidzadeh, , 1982Tosi, 1989). Furthermore, it was used to produce pigments and glaze colourants during later periods, such as the Islamic era on the Iranian Plateau and surrounding areas (e.g., Colantonio et al, 2021;Colomban, 2003; Couvrat F I G U R E 6 (a) Bivariate scatter plot of S/Si versus Cl/Si in the composition of Persepolitan samples as well as some lapis lazuli resources around the world based on Zöldföldi and Kasztovszky (2009); (b) bivariate scatter plot of Ba versus Sr in the composition of Persepolitan samples as well as data from the analysis of archaeological samples and resources in Central Asia and southern Asia (Casanova, 1992); and (c) bivariate scatter plot of Ni versus Cu in the composition of different types of pyrite observed in the scanning electron microscopy-backscatter electron (SEM-BSE) images of samples showing the compositional patterns similar with Badakhshan quarries (Lo Giudice et al, 2017). Desvergnes et al, 2021;Koochakzaei et al, 2022).…”

Spectral Mapping Techniques for the Stratigraphic and Compositional Characterisation of a 16th-Century Painting

“…Possible misinterpretation of SC maps can be related to the fact that multispectral reflectography does not offer sufficient spectral resolution to detect subtle differences between optically similar pigments, such as indigo and lapis lazuli, or black organic pigments. For a more accurate identification, non-invasive vibrational and infrared spectroscopies could be used [30]. In the specific case of St Elizabeth's dress, it is likely that a red pigment, not identified by RIS, was mixed with smalt and lead white to produce the purple hue.…”

Deep Spectral Imaging (DSI): an optimized AI-based spectral imaging acquisition, transmission, and calibration

“…The images calibration process is shared by both UAV and satellites solutions. It is based on the Hypercolorimetric Multispectral Imaging technology (HMI) that was born in 2013 [1] to support diagnostics and pigment identification in the field of Cultural Heritage [2].…”