Ancient Chinese glass refers to all types of glass manufactured in China prior to the Qing Dynasty (1644–1911). In Chinese history, glass played a peripheral role in arts and crafts, when compared to ceramics and metal work. The limited archaeological distribution and use of glass objects are evidence of the rarity of the material. Literary sources date the first manufacture of glass to the 5th century AD. However, the earliest archaeological evidence for glass manufacture in China comes from the Warring States period (475 BC to 221 BC).
Chinese learned to manufacture glass comparatively later than the Mesopotamians, Egyptians and Indians. Imported glass objects first reached China during the late Spring and Autumn period – early Warring States period (early 5th century BC), in the form of polychrome ‘eye beads’. These imports created the impetus for the production of indigenous glass beads.
During the Han period (206 BC to 220 AD) the use of glass diversified. The introduction of glass casting in this period encouraged the production of moulded objects, such as bi disks and other ritual objects. The Chinese glass objects from the Warring States period and Han Dynasty vary greatly in chemical composition from the imported glass objects. The glasses from this period contain high levels of barium oxide (BaO) and lead, distinguishing them from the soda-lime-silica glasses of Western Asia and Mesopotamia. At the end of the Han Dynasty (AD 220), the lead-barium glass tradition declined, with glass production only resuming during the 4th and 5th centuries AD.
Chemical composition of Warring States and Han period glasses
At present, it is accepted that in China, glassmaking began around the 5th century BCE during the late Spring and Autumn to early Warring States periods. Chemical analyses of glass samples dating to this time have identified no less than three glass systems: potash-lime, lead-barium, and potash; of these, lead-barium was the most significant in early China.
During the Warring States period and the Han Dynasty (5th century BC to early 3rd century AD) glass was imported from regions outside of East Asia, such as Mesopotamia. Imported Western faience and glass probably inspired the production of the first Chinese glasses. The main group of objects with Western influences are eye beads or dragonfly-eyed beads. The key difference between Near Eastern eye beads and Chinese eye beads is their chemical composition. The coloured glasses used to produce the Chinese eye beads have a high lead and barium content. This type of composition was exclusive to China; and it was used to produce a range of glass objects until the end of the Han Dynasty.
Table 1 shows examples of chemical compositions of some Chinese glass objects.
Table 1: Elemental compositions of Chinese glass from the Warring States Period to Han Dynasty. Data from the first 4 objects was taken from Brill et al. 1991; data from glass garment plaque was taken from Cheng Zhuhai and Zhou Changyuan 1991; and data from the ritual disk was taken from Shi Meiguang 1991.
The Chinese lead-barium glasses typically present 5 to 15% BaO. The source of barium in the glass in not clear; however it is possible that ancient Chinese glassmakers used witherite (a mineral form of barium carbonate) as an ingredient. The use of a separate ingredient implies that barium had a specific function. This function could have been to flux the glass, by lowering the melting point of the melt; or stabilize the glass, by making it less soluble to water. It could also have been added to opacify the glass. Electron microprobe analysis of glass fragments have shown that the turbidity of certain lead-barium glasses is produced by barium disilicate crystals. This turbidity gives the glasses a jade-like appearance.
Glass objects in the Warring States and Han Periods
The period between the Warring States period and the Han Dynasty shaped the early Chinese glass industry. Most of the glass objects from this period come from archaeological excavations of tombs. Because of this, most glass objects have fairly secure dating and context. During this period Chinese mainly used glass to produce two distinct types of objects, polychrome eye beads and monochrome funerary objects