AMS radiocarbon dating of dyed Coptic textiles from the Kyoto University Museum: fiber-specific pretreatment and chronological assessment

Accelerator mass spectrometry (AMS) radiocarbon dating was applied to three dyed Coptic textiles housed at the Kyoto University Museum. For Reg. Nos. 1126-8 and 2162-2, AMS dating used previously detached material that had been retained by the museum; for Reg. No. 2162-7, a minimal sample was intentionally removed in an amount judged not to affect the integrity or visual appearance of the object. Previous analytical work associated Reg. No. 1126-8 with shell purple, Reg. No. 2162-2 with a coccid-derived red colorant, and Reg. No. 2162-7 with madder. Following solvent cleaning and fiber-specific acid–base–acid pretreatment, the samples were graphitized and measured using a compact 0.5 MV tandem AMS system. For Reg. No. 1126-8, separately measured warp and weft yarns yielded conventional radiocarbon ages of 1610 ± 20 BP and 1585 ± 20 BP, corresponding to cal AD 408–535 and cal AD 425–537, respectively, at 95.4% probability. Reg. No. 2162-2 dated to cal AD 776–887 at 95.4% probability, whereas Reg. No. 2162-7 yielded two calibrated intervals, cal AD 386–466 (70.9%) and cal AD 481–534 (24.5%). AMS-derived δ 13 C values of −21.66‰ and −14.39‰ were obtained for the warp and weft of Reg. No. 1126-8. Because these values were generated for isotopic-fractionation correction rather than by dedicated isotope ratio mass spectrometry, the observed difference is treated only as a preliminary analytical observation. The results provide direct chronological evidence for three museum textiles with incomplete archaeological documentation and demonstrate the importance of fiber-specific pretreatment in AMS dating of fragile dyed textiles.