A Study on the Morphology and Material Characteristics of Twisted Gold Threads From the Tang Dynasty Unearthed at the Tuyugou Grottoes in Xinjiang
LIU Da-wei1, 2, GU Yu-shan2*
1. Key Laboratory of Science and Technology in Archaeology and Conservation of Cultural Heritage, Chinese Academy of Social Sciences, Beijing 100710，China
2. Beijing Institute of Fashion Technology, Beijing 100029，China
Abstract：This study focuses on four sets of twisted gold thread samples from Tang Dynasty lotus-patterned embroidered banners unearthed at the Tuyugou Grottoes site in Turpan, Xinjiang. A range of modern analytical techniques, including optical microscopy (OM), scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS), laser confocal Raman spectroscopy (Raman), and fiber microscopy identification, were employed to systematically investigate their structural morphology, metal and fiber composition, as well as the corrosion products and their formation mechanisms. The results show that the average width of the metal strips used in the twisted gold threads ranges from 480 to 498 μm, with a thickness of 30 to 50 μm. SEM-EDS elemental analysis reveals that the metal strips are primarily composed of copper-zinc alloys, with approximately 2 wt% zinc content. The corrosion products on the surface mainly include copper(Ⅰ) oxide (Cu2O), atacamite [Cu2(OH)3Cl], and copper zinc chloride hydroxide [Cu3Zn(OH)6Cl2]. Based on the distribution of the corrosion products, it is speculated that significant dezincification corrosion occurred in the buried environment, with localized Cl element enrichment on the surface, leading to the formation of chloride copper corrosion products. Furthermore, Raman spectroscopy confirmed the presence of the aforementioned corrosion phases: the red substance was mainly copper(Ⅰ) oxide, the green substance was a mixture of atacamite and copper zinc chloride hydroxide, and the black substance exhibited a clear carbon black signal, which is suspected to originate from soot deposited during religious offerings such as incense and candles. In terms of manufacturing techniques, the metal strip edges are smooth with no signs of pulling, and its uniform width and thickness suggest that the copper alloy was hammered into thin sheets and then cut into strips, which were spirally wound around cotton core fibers either by hand or using simple tools. Microscopic observation of the core fiber shows a natural twist in the longitudinal direction, a distinct central cavity, and a typical kidney-shaped cross-section, confirming that the core material is cotton fiber. Twisting tests revealed that the core fiber is a two-ply Z twist, and the metal strip is an S twist, consistent with the typical structural characteristics of traditional twisted gold thread. In conclusion, this study reveals the fundamental characteristics of the Tang Dynasty twisted gold threads from the Tuyugou Grottoes, including material selection, structural design, decorative techniques, and corrosion behavior. Although these metal decorative textiles do not use precious metals, the use of brass material with gold-like treatment, the two-ply cotton core, and the reasonable design of the manufacturing process balance visual effects and cost control, highlighting the unique and regional development of decorative techniques in religious textiles along the Silk Road.
刘大玮，谷雨珊. 新疆吐峪沟石窟出土唐代捻金线形貌与材质特征研究[J]. 光谱学与光谱分析, 2025, 45(11): 3216-3225.
LIU Da-wei, GU Yu-shan. A Study on the Morphology and Material Characteristics of Twisted Gold Threads From the Tang Dynasty Unearthed at the Tuyugou Grottoes in Xinjiang. SPECTROSCOPY AND SPECTRAL ANALYSIS, 2025, 45(11): 3216-3225.
[1] JY/T 0584—2020, General Rules of Analytical Methods for Scanning Electron Microscope（扫描电子显微镜分析方法通则）[S]. 2020.
[2] FZ/T 01057.3—2007. Test Method for Identification of Textile Fibers—Part 3: Microscopy Method（纺织纤维鉴别试验方法第3部分显微镜法）[S]. 2007.
[3] ZHANG Ya-ying（张亚莹）. Structure and Design of Color-Woven Fabrics（色织物组织与设计）. Beijing: China Textile Industry Press（北京: 纺织工业出版社）, 1987: 13.
[4] David A Scott(大卫·斯考特著）. Copper and Bronze in Art: Corrosion Products, Pigments, and Conservation（艺术品中的铜和青铜腐蚀产物，颜料，保护）. Translated by MA Qing-lin, PAN Lu（马清林，潘 路，译）. Beijing: Science Press（北京: 科学出版社）, 2009.
[5] CAO Ning (曹 宁). Master Dissertation(硕士论文). Beijing University of Civil Engineering and Architecture (北京建筑大学)，2021.
[6] GB/T 5231—2022. Designation and Chemical Composition of Wrought Copper and Copper Alloys（加工铜及铜合金牌号和化学成分）[S]. 2022.
[7] ZHOU Lu-ying（周璐瑛）. Modern Clothing Materials Science（现代服装材料学）. Beijing: China Textile Press（北京:中国纺织出版社）, 2000.
[8] LU Zhi-yong（路智勇）. Huaxia Archaeology（华夏考古）, 2018, (2): 106.
[9] LU Zhi-yong, HUI Ren, YANG Jun-chang, et al（路智勇, 惠 任, 杨军昌，等）. Archaeology（考古）, 2022, (6): 112.
[10] DANG Xiao-juan, GUO Jin-long, BAI Ke, et al（党小娟, 郭金龙, 柏 柯，等）. Sciences of Conservation and Archaeology（文物保护与考古科学）, 2014, 26(3): 13.
[11] ZHENG Shuo-zai, LI Hao-miao, WENG Lian-xi, et al（郑烁在, 李浩淼, 翁连溪, 等）. Spectroscopy and Spectral Analysis（光谱学与光谱分析）, 2023, 43(6): 1781.
