Selected Coptic textiles from the collection of the Egyptian Museum of Turin: a non-invasive survey on dyeing materials

The Coptic collection of the Egyptian Museum of Turin includes about 250 textiles. Many of them are decorative parts that have been cut out from tunics or fragments deriving from larger textiles, although the collection also encompasses whole tunics and headdresses. The conditions of the textiles are largely inhomogeneous: some of them are excellently preserved whereas others are in bad conditions possibly due to restorations that were undertaken at the beginning of the past century. A minor part of the collection derives from Schiaparelli's excavation in Ashmunein (Hermopolis), while the provenance of most of the textiles, which were donated to the Turin Museum by the Cairo Egyptian Museum at the beginning of the 1900, is unknown. In order to shed light on provenance, date of production, conservation and materials, and to highlight possible similarities or differences among the fragments, a selected set of Coptic textiles presently stored for studying and cataloguing is the object a multidisciplinary project that will consider the textiles from an iconographic and technological point of view. In particular, the project is focused on the study of textiles fibers and weaving technologies under the optical microscope, as well as on the application of non- invasive and invasive analytical techniques in order to investigate the dyeing materials. A non-invasive screening was performed by UV-Vis-NIR reflectance spectroscopy [1] and fluorimetry [2,3] employing portable instruments equipped with fiber optics that allowed an in situ survey. Due to the bad conditions of some textiles, more robust information can be obtained by performing a large number of analysis on the same object and by considering together the information obtained from the two analytical techniques. Both fiber optics reflectance spectroscopy (FORS) and fiber optics fluorimetry respond in few seconds and allow the rapid highlighting of some peculiar information on the dyes. In particular, the presence of indigo is easily detected by FORS, and also the vegetable or animal nature of some anthraquinonic red dyes can be assessed. Moreover, the techniques also allowed us to sort out, among the red or reddish hues, those that could not be attributed to the presence of the most popular red dyestuffs (i.e. rubia species and coccids). Unfortunately the non-invasive approach lacks in information for yellow dyestuffs, although groups of samples were identified according to few common spectroscopic features. The overall investigation allowed us to obtain preliminary information on the dyestuffs employed and to recognize the presence of different materials employed to obtain similar hues. Moreover, the non-invasive survey allowed us to select a limited number of representative samples to be subjected to further analysis.