The formation of the gold layer in mercury gilding occurs through the heating a gold amalgam. As a result, the formation mechanism and technical characteristics of gilded products are closely related to the temperature at which they are heated. In this study, XRD and XPS analysis of a copper-gilded coronet from the Sui or Tang dynasties revealed that Au3Cu was one of the main phases of the gold layer. Therefore, base on the thermodynamic stability of ordered phases like Au3Cu, the estimated heating temperature for this copper-gilded coronet ranged from 240 to 285 ℃. Furthermore, SEM–EDS analysis of the cross-sectional concentration distribution of Cu indicated that the diffusion distance of Cu during heating did not exceed 2 μm. At 240–285 ℃, Cu diffused along the defects of the gold layer, and the diffusion process followed Fick’s second law. Previous research has indicated that the defect path diffusion coefficient of Cu is on the order of 10–12 cm2/s, and the heating time of the gilding process is typically considered to be 15 min. Using the diffusion equation, the calculated diffusion distance of Cu aligned with the diffusion behavior of Cu at 240–285 ℃, confirming the inferred heating temperature range. Additionally, at these temperatures, the gold layer was formed through the solid-state reaction of the gold amalgam and was bonded to the substrate through the diffusion of Cu.

Ancient Chinese brass smelting technology has promoted the invention of zinc smelting, thus becoming an important part of the metallurgical history. However, the information concerning its origin and development is still controversial. In that regard, thorough analysis of composition and structure of the early brass is crucial for studying various stages of the ancient brass smelting technology history. This study aimed to investigate brass artifacts from Kunlun M2 tomb in Xi'an, Shaanxi, dating back during Sui to early Tang Dynasty (581–712 AD). The composition and metallographic characterization of the materials was performed using XRF, SEM–EDS and metallographic analysis. According to the results, brass was composed of 83 wt% of copper, 12 wt% of zinc, and 3 wt% of tin. Furthermore, its microstructure consisted of α-isometric single crystals with some slip lines and a few twinned grains. This indicated that brass was obtained by melting an appropriate mixture of zinc ores and copper ores at a temperature above 920 °C. Furthermore, brass support components were installed on the coronet after integral hot forging and partial cold shaping. Besides, the use of brass in the coronet was in conformity with the social hierarchy of that historical period, and also reflected the attention paid to the properties of materials.

A woman’s crown made of fine gilt bronze with refined glass inlay work was excavated from a Sui-Tang tomb called Kunlun M2 in Xi’an, Shaanxi Province, China. Very few female crowns and crown ornaments have been excavated in China thus far, and there has been a lack of systematic research into the technologies used to manufacture them. Importantly, this paper uses the M2 crown to investigate its surface inlays and overall shape, then conducts a comparative analysis of women's crown ornaments of the same type, providing a reference for study of the crown. Non-invasive and micro-destructive analysis including optical microscopy (OM), optical coherence tomography (OCT), micro X-ray fluorescence imagery (XRF), and Raman spectroscopy were applied. These identified the crown’s inlays as potash-lime glass, composed mainly of the raw materials: vein quartz or quartzite with potassium nitrate as flux. The inlays were sintered before embedding into gilt copper wire filigree. In comparison to the composition proportions in other ancient potash-lime glass, there is no specific percentage of the raw materials in Chinese potash-lime glass, where the ingredients were likely determined by the experience of the craftsman. Compared with existing research on other crowns and their inlays, this study speculates that the crown dates from the Sui dynasty (581–618) or early Tang dynasty (618–649), was made locally by Chinese craftsmen and belonged to the wife of a high official.

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A woman’s crown made of fine gilt bronze with refined glass inlay work was excavated in 2007 from the Sui-Tang tomb called Kunlun M2 in Xi’an. Many questions surround this mysterious crown which was found buried without context. This study uses nondestructive analysis of the crown to determine its significance, when was it made, and the status of the woman for whom was it made. Optical microscopy (OM), optical coherence tomography (OCT), micro X-ray fluorescence imagery (XRF), and Raman spectroscopy were applied, and identified the crown’s inlays as potash-lime glass, composed mainly of the raw materials include vein quartz or quartzite with potassium nitrate as flux. The inlays were sintered before embedding into gilt copper wire filigree. Compared with existing research on other crowns and their inlays, it is speculated that the crown dates from the Sui dynasty (581-618) or early Tang dynasty (618-649), was made locally by Chinese craftsmen and belonged to the wife of an official.