Abstract: Silk fabrics have a long history in China. They are also an important part of Chinese civilization. Silk fabrics are natural polymer compounds, which are easily damaged by light, temperature, humidity, microorganisms and so on. It is different to preserve cultural relics permanently. Therefore, studies on the protection of ancient silk are particularly crucial. Among them, the origin of ancient silk has always been hotly discussed. As a new technology in modern ecological research, stable isotope technique has become a powerful tool for the traceability of silk fabrics with its advantages of tracing, indication, fast detection and accurate results. During the preservation process of ancient silk, the original pollutants may cause significant changes in the structure and isotopic information of silk fabrics, thereby affecting the accuracy of provenance tracing. Therefore, in order to use isotope technology to trace the origin of ancient silk, it is necessary to figure out how the isotopic information of silk has changed during the cleaning process,.
To explore the influence of cleaning treatment on the morphology, structure, and stable isotope of the ancient silk from the Ming Dynasty, silk fabric samples were simply cleaned by four gentle cleaning methods (deionized water cleaning, ethyl alcohol cleaning, deionized water/ethyl alcohol cleaning, and steam cleaning). The surface morphology, structure and stable isotope ratios of silk samples before and after cleaning were examined by using scanning electron microscope (SEM), fourier transform infrared spectrometer (FTIR), thermal gravimetric analyzer (TGA) and isotope mass spectrometer. The results indicate that deionized water and ethyl alcohol had certain cleaning effects, while steam cleaning caused secondary pollution on the surface of the silk, requiring further removal of contaminants. The relative content of β-sheet in the fibroin decreases after steam cleaning. After cleaning treatment, the hydrogen stable isotope ratio of silk samples decreased, the oxygen stable isotope ratio increased, the carbon stable isotope ratio had little change within 0.30‰, while the variation of nitrogen stable isotope ratio showed no clear appearance. The research results provide certain reference for eliminating external interference and conducting data correction in tracing the origin of ancient silk. 

Key words: silk fabric, cleaning, FTIR, secondary structure, stable isotope

摘要： 为了探究清洗处理对明代传世丝绸的形貌、结构及稳定同位素的影响，选取去离子水、乙醇、去离子水/乙醇和蒸汽清洗4种温和的清洗方法，对丝绸文物进行简单清洗，并使用扫描电镜、傅里叶变换红外光谱仪、热重分析仪和同位素比质谱仪对清洗前后丝绸文物的表面形貌、结构和稳定同位素比值进行表征。结果表明：前3种方法均有一定的清洗效果，而蒸汽清洗会造成丝绸表面的二次污染，需要进一步去除污染物；蒸汽清洗使样品的丝蛋白中β折叠构象相对含量减少；清洗后丝绸文物中氢稳定同位素比值减小，氧稳定同位素比值增大，碳稳定同位素比值变化不大，在0.30‰以内，而氮稳定同位素的变化规律相对不明显。因此利用稳定同位素技术对丝绸文物进行溯源时，要考虑清洗处理对丝绸文物稳定同位素比值的影响。研究结果可为丝织品文物溯源时排除外源性干扰、进行数据校正提供一定的参考。

关键词: 丝织品, 清洗, 红外光谱, 二级结构, 稳定同位素