cristina scibe

For thousands of years metal threads have been used for the decoration of textiles and clothes to create luxurious objects. Between the 11th and the 15th centuries, gilt and silvered organic strips (made with animal skin, animal gut or paper) were among the metal threads most commonly used, either as flat strips or wound around a fibrous core. These types of metal threads were very popular due to their flexibility and reduced cost; indeed, the metal coating was applied in one or multiple thin layers on the organic substrate that made up most of the thickness of the thread.
While the use of paper as substrate was restricted to East Asia, animal substrates were widely used across Europe and Asia resulting in what has been called “membrane threads”. The metal-coated organic threads have a layered and heterogeneous structure, of which the metal layer has mostly been the target of investigation due to the complexity of studying the organic component. In the present work, metal-coated skin threads from medieval Spanish, Sicilian, Middle Eastern, Central and East Asian textiles were investigated by a multi-analytical approach, combining for the first time Optical Microscopy, Scanning Electron Microscopy/Energy Dispersive X-Ray Spectroscopy and Proteomics.

Animal-based metal threads were largely used between the 10th and the fifteenth century, in European, Middle Eastern and Far Eastern textile productions for the decoration of textiles and cloths. They belong to a larger group of metal threads, used either as flat threads or wrapped around a fiber core, that were backed by an organic support (animal or paper). This study focuses on the medieval production of metal threads backed by an animal membrane (e.g. gut membrane), or skin. A total of 91 samples were collected from a corpus of 66 textile fragments belonging to 54 catalogued objects. The relevance and novelty of the present study is represented by the combination of proteomics, cross-section analysis, and scanning electron microscopy (SEM-EDS and SEM-µXRF). The diversity of materials and manufacturing techniques found within each typology of thread, respectively, membrane-based metal threads and skin-based metal threads, hinted at different production technologies. Membrane-based threads were found to be invariably made from cattle gut membrane, coated with gilt-silver leaves. A possible sheep glue adhesive was found in a few samples. Skin-based threads were made from either goat or sheep leather, coated with metal leaves or powder. Within the three different types of coatings identified (silver, gold and gilt-silver), gold coatings were the most represented. Goat leather threads were associated with an egg-white binder, while sturgeon glue was identified as adhesive in all sheep leather threads. Collagen glue from other species (cattle, sheep, horse) was occasionally found in mixed adhesives. In two textiles, the finding of human proteins indicates past contamination due to handling or use. The analytical results show coherence between the fabrication patterns of animal-based metal threads and their probable geographical areas of manufacture, indicating that the study of materials and techniques provide further criteria to classify and group textiles, and trace correlations between manufacturing centers within Eurasian territories.