Non-invasive study of natural dyes in textiles of the Qing Dynasty using fiber optic reflectance spectroscopy

Four kinds of fibers with 11 traditional natural dyes were measured using a portable spectrometer equipped with optical fibers working in reflectance mode (fiber optic reflectance spectroscopy, FORS) in the ultraviolet to near-infrared (NIR) regions. The absorption spectra of Kubelk-Munk transformation in ultraviolet-visible (UV-vis) region were demonstrated to be valid for analysis of dyes on textiles and the characteristic absorption spectra of fiber in near-infrared region provide information to discriminate the type of fibers. The technique was applied to examine a collection named of 'Lohan Rubbing' of Qing Dynasty from Tibet Museum, then the established spectra library was further applied to analyze the collection. With the comparison to the references of spectra library, sappanwood, madder, indigo and amurcork tree were successfully identified in the inlay colored textile. The mixture of sappanwood and indigo for the purple color, amur-cork tree and indigo for the green color were detected. The application of portable fiber optic reflectance spectroscopy provides a rapidly and non-invasive way for natural dye identification in historical textiles and it is beneficial to large-scale on-site survey. (C) 2020 Elsevier Masson SAS. All rights reserved.