The non-invasive approach to the analysis of dyes and pigments in the Medieval Persian manuscripts

“Persian manuscripts” is used to indicate paper books written by hand in Persian language coming from a wide geographical area in different epoch and dealing with various subjects. The influence of Persia led to the production of manuscripts with common linguistic-textual features also over the borders of political influence. The taste for the chancellery, courtier and academic Persian models was acquired by the rulers of the Empire of Turkish-Mongol origins and widespread along the Iranian plateau as far as ottoman Turkey and the Indian Mughal Empire. Since the Persian Era, writing had an enormous importance, because it represented the state and the religion; this role is further stressed with the advent of Muslim religion, as the Koran is the holy book from which writing is born. As a consequence, calligraphers were highly considered in the Persian society and were asked to move across and over the Persian territories together with painters, paper-makers and other artisans connected to the production of manuscripts, thus creating a common taste for books in a large geographical area. The art of Persian manuscripts has been surviving for over a millennium and came to its end only at the beginning of 20th century, but the golden era of these artworks lasts from the 14th to the 17th century AD. The knowledge of the materials employed to write and decorate Persian manuscripts is available to modern Persians thanks to ancient treatises about illumination, calligraphy and paper decoration. However, people who are not familiar with fārsì can recover information from the paper of Purinton and Watters [1]. The authors overviewed the materials of Persian handwriting by reporting the information given in two books (Qanun us-Suvar by Sadiqi Bek and Gulistan-i Hunar by Quadi Ahmad) dated at the 16th and 17th century, respectively. From the point of view of the analyst, colorants in Persian manuscripts can be detected by an instrumental analytical approach. In particular, it is generally possible to recognize the inorganic pigments by combining non-invasive analytical techniques such as reflectance spectroscopy, X-ray fluorescence and Raman spectroscopy. Organic dyes are barely mentioned in the paper of Purington and Watters, although evidence of their large use emerged by considering some volumes kept in libraries in Italy which were investigated in situ by UV-visible diffuse reflectance spectrophotometry (FORS), spectrofluorimetry and X-ray fluorescence spectrometry (XRF). Dyes were employed to dye the paper support and to impart delicate hues to particular details in miniatures. In order to build up a spectral data-base devoted to dyes possibly employed in Persian manuscripts, a set of mock-up samples was prepared by considering natural dyestuffs indicated in the comprehensive book of Nadjib Mayil Harawi [2], which collects articles dealing with penmanship, ink making, papers, gilding and book binding. The paper employed as a support was obtained from hemp by miming historical procedures [3] whereas Althea officinalis, Anemone coronaira, Lawsonia inermis, Berberis vulgaris, Rheum undulatum, Curcuma longa and Crocus sativus were considered as sources of dyes. The plants were treated according to ancient recipes to extract the dyes and used to dye or paint the paper substrate. FORS and spectrofluorimetry equipped with fibre optics were then employed to record the spectral features of the mock-up samples. The information obtained on mock-ups were then considered, along with those already obtained on previously prepared reference samples, for the interpretation of reflectance and fluorescence spectra that were recorded on the collection of Persian manuscripts owned by the Museo di arti orientali (Museum of eastern art) in Torino (Italy). Manuscripts were also investigated by employing portable XRF, in order to gain information on both organic and inorganic colorants.