Assessment of a multi-technical non-invasive approach for the typology of inks, dyes and pigments in two 19th century's ancient manuscripts of Morocco

A rich and non-invasive multi-technique study has been carried out on two ancient Moroccan manuscripts, dealing with theology, written in the 19th century and belonging to different scribal schools of the western Arabic Mediterranean region. Currently, Moroccan manuscripts investigations are limited to codicological studies in which reports on illuminations and colored vocalizations are limited to visual descriptions. Hence scientific investigations are required for an objective characterization of this universal heritage. The integration of elemental and molecular information acquired by μ-XRF, μ-XRD, μ-Raman, μ-SERS, reflection mid-FTIR, UV–vis reflectance and UV–vis fluorescence has allowed for the characterization of both inorganic pigments and organic dyes. The inorganic pigments have been identified and characterized by combining the elemental XRF information with molecular infrared and Raman investigations. XRD analyses have been also carried out for the identification of crystalline compounds. Vermillion, orpiment, azurite, lead chromate, emerald green, Scheele's green and artificial ultramarine were identified. Red and yellow organic dyes have been identified by combining SERS, UV–vis reflection and UV–vis fluorescence spectroscopic techniques. The signals detected on red colors were assigned to the animal carminic anthraquinone, while those detected on yellows seem originating from a natural flavonoid. The present study, which is the first complete one undertaken on ancient Islamic documents of Morocco and being extended in situ to other artworks, unique in the Arabic world and available at the Moroccan libraries, will contribute to promoting codicological investigations, dating and authenticating some manuscripts and giving elements of response, useful for art history, in the knowledge of coloring materials used in the western Mediterranean Arabic region during the 19th century.