Paper fragments from the Tibetan Samye Monastery: Clues for an unusual sizing recipe implying wheat starch and milk in early Tibetan papermaking

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The origin of Tibetan papermaking is poorly documented. Up to now, only the Tibetan paper fragments from Endere and Dunhuang sites have been scientifically studied outlining the basic knowledge about plant fiber uses and artwork manufacturing procedures. In order to deepen the knowledge on the unique ancient Tibetan papermaking, we report here the analysis of a set of paper fragments from the Samye Monastery in south Tibet, China. Multidisciplinary scientific investigations utilizing 14C radiocarbon dating, microscopic observation, scanning electron microscopy (SEM), pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS), pyrolysis-comprehensive gas chromatography/mass spectrometry (Py-GCxGC/MS), and proteomic analysis have been applied to these ancient paper fragments. The results show that the fragments were dated to the 12th~13th century AD and made from fibers of the Thymelaeaceae family plant Stellera Chamaejasme L of which the fiber’s chemical profiles have been firstly studied. The presence of starch granules from Triticum spp wheat and proteins from bovine milk (more likely assigned to native yak), offers the first indication that a unique sizing technique using starch-milk sizing had been employed in early Tibetan papermaking, compared to using alum-animal glue sizing agent which is more popular in contemporary Central China. The combined use of organic material (unaltered starch grains) and inorganic material (calcium carbonate) as paper fillers is also firstly revealed in Tibetan papermaking. The application of Py-GC/MS, Py-GCxGC/MS and proteomic analysis revealed more detailed profiles of early Tibetan hand papermaking, indicating that these methods have great potential to explore the production technology of ancient handmade papers.