Glass in China Emily Byrne Curtis* Independent Scholar and Researcher, Hoboken, NJ, USA

Glass has always occupied a marginal position in China. From the earliest times, it has exhibited a varied composition reflecting the disparate sources for raw materials, and it was further complicated by the occasional mingling of Western glass in the manufacturing process. For instance, chemical analysis of early glass artifacts found in China showed that they had been made with soda (SiO2) and lime (Na2O), of Western Asian origins. The fact that these specimens came mainly from the coasts of Guangxi and Guangdong provinces in southern China indicated that this glass, in the form of ingots or finished products, was imported through the maritime route. Glass was also shipped in large quantities as cullet (glass lumps and discarded broken vessels), suitable for re-melting and making new glass inexpensively. Thus, while it is not always possible to establish the uniqueness of Chinese glass from a chemical standpoint, analyses have been able to shed light on its various components and provide us with a timeline for its evolution . The glassmaking process itself can be roughly divided into two phases, the first of which was reducing the raw materials to a powder after which they were fused in furnaces capable of reaching high temperatures. In the second phase, the molten glass (called metal) was ladled or poured into molds and pressed, blown, or drawn. The finishing process could be done either at the original glass workshop or carried out elsewhere. Also, it might suggest that a subdivision of labor existed between craftsmen who knew how to mix the raw materials and manipulate the furnaces and other artisans who were skilled in blowing or carving the glass. The Initial Stage Studies of Chinese glassmaking were initially limited to literary sources which placed the beginnings of the craft in the fifth century BC. However, more recent archaeological excavations in China have uncovered evidence which indicates that production may have started in the late Zhou dynasty (1046–221 BC). The shapes of the excavated round and cylindrical glass beads indicated a definite influence from jade and stoneworking, and Western Zhou glass may well be the first glass made in imitation of jade. However, since the chemical compositions for some of the beads are dominated by SiO2, and there are large amounts of crystalline quartz present, some scholars argue that this material is not really glass but faience. The sword decorations generally proved to be transparent glasses, of the calcium-silicate (X-CaO-SiO2) or potassium-calcium-silicate (K2O-CaO-SiO2) variety. While glassblowing was invented in the Middle East, perhaps in Syria, about 50–25 BC, this technique developed later in China. Given that Bactrian glassblowers are believed to have been working at Datong, Shanxi province, during the Northern Wei (386–581 AD) period, the question arises as to when and if they passed on this technique to Chinese craftsmen. Therefore, the glass vessels from this period, which were found in a stupa in Jingxian, Hebei province, have been considered as important. The cache contained three gourd-shaped bottles, two other bottles, and a monk’s alms bowl. All of them were blown of domestic (Chinese) glass. This was an important turning point in the history of Chinese glassmaking, because it made mass production possible and glass products less expensive.

Glass Workshops at Boshan Written records inform us that glass hair clasps were produced in the Tang dynasty (618–907 AD) and that in the Song dynasty (960–1279 AD) the majority of women were wearing hair ornaments made from glass. Some examples of rings and hairpins in opaque off-white or turquoise glass may well be products of the glassworks in Zibo, Shandong.

The remains of an ancient glass factory, dating to at least the late Yuan to early Ming, were discovered in 1980s by the edge of the Shaofu River in Boshan (Zibo). The subsequent excavation of this site uncovered pieces of glass, the remains of clay pots, their covers, and some 20 furnace pits arranged in a line. Chemical analyses of the glass shards revealed that they contained a high level of calcium and a low level of lead. When tested, a sample of blue opal glass was found to contain fluorine and that the lime found in this specimen could be accounted for by the presence of fluorspar. It was determined that the melting furnaces had been fueled by coke, which is also noted in ancient Chinese literature. Two basic ways of forming glass were employed. Items like hair clasps were made from glass rods or tubes by a secondary process; they were reheated and then formed. Button-like ornaments were made by reheating and molding. These glass objects represented an alternative to jade, a much cherished and more expensive material. They also represented an expanded repertoire since many of Fig. 3 Glass, molded as a recumbent boy supporting his head on his hands, Qing dynasty (seventeenth/eighteenth century), L. 11.9 cm. ex Collection, Dr. Alan E. Feen Fig. 4 Glass, brush washer of opaque ivory with ruby-red carved overlays, lip rim with incised four-character Qianlong mark (1736–1795) on rim, D. 8.3 cm. ex Collection Dr. Alan E. Feen Encyclopaedia of the History of Science, Technology, and Medicine in Non-Western Cultures DOI 10.1007/978-94-007-3934-5_10183-1 # Springer Science+Business Media Dordrecht 2014 Page 3 of 8 the glass objects found in earlier burial contexts were made with shapes similar to their jade counterparts. This imitation was intended to replicate the shape and significance of jades – a major distinctive feature of Chinese glass and also one of the distinguishing marks between Chinese and western glassware. The unusually high concentration of barium oxide (BaO) in the composition of early Chinese glass produced a certain turbidity in the metal which might have been regarded as desirable by the craftsmen since it gave the glass a jade-like appearance. This trait is quite apparent in opaque, white glass artifacts. Sun Tingquan’s Yanshan zaji (Mt. Yanshan Records) dates to 1665. In it Sun gives a systematic and informative account of the glass materials, properties, coloring, melting times, tools, products, and distribution at Boshan. According to Sun, the glass was made entirely from local materials such as feldspar, fluorspar, quartz, and niter. He also comments upon the creativity of the craftsmen in contending with a lack of sophisticated tools and instruments. What is of particular note here is that Boshan was a major glassmaking center which, due to a series of natural disasters, had ceased operation by the end of the Ming dynasty. Under the patronage Fig. 5 Glass, aventurine, pierced and cut to resemble a scholar’s rock, H. with stand 9.2 cm, nineteenth century. Collection, Robert H. Blumenfield Fig. 6 Glass, diamond-engraved on exterior with four lotus sprays, divided by stylized clouds, D. 12 cm, late seventeenth to early eighteenth century. ex Plesch collection Encyclopaedia of the History of Science, Technology, and Medicine in the glass objects found in earlier burial contexts were made with shapes similar to their jade counterparts. This imitation was intended to replicate the shape and significance of jades – a major distinctive feature of Chinese glass and also one of the distinguishing marks between Chinese and western glassware. The unusually high concentration of barium oxide (BaO) in the composition of early Chinese glass produced a certain turbidity in the metal which might have been regarded as desirable by the craftsmen since it gave the glass a jade-like appearance. This trait is quite apparent in opaque, white glass artifacts. Sun Tingquan’s Yanshan zaji (Mt. Yanshan Records) dates to 1665. In it Sun gives a systematic and informative account of the glass materials, properties, coloring, melting times, tools, products, and distribution at Boshan. According to Sun, the glass was made entirely from local materials such as feldspar, fluorspar, quartz, and niter. He also comments upon the creativity of the craftsmen in contending with a lack of sophisticated tools and instruments. What is of particular note here is that Boshan was a major glassmaking center which, due to a series of natural disasters, had ceased operation by the end of the Ming dynasty. Under the patronage of the Qing emperors, it was able to resume its role as a center of Chinese glassmaking, supplying both materials and craftsmen to the imperial glass workshop; it remains active in present-day China. Imperial Glassmaking Qing dynasty (1644–1911) glass deserves an important place in the history of Chinese glass. In the 35th year (1696) of Kangxi (r. 1662–1722), an imperial glass workshop was established under the direction of Kilian Stumpf, SJ (Ji Lian). Under the patronage of Qing rulers, many new varieties of glass were made, and it was an outstanding period of artistic accomplishment. K2O and PbO, which were used as fluxes in ancient Chinese glasses preceding the Qing dynasty, proved to be the main fluxes of the glasses analyzed of samples in the Beijing Palace Museum. The raw glass materials used by the imperial workshops included “horse-tooth stone,” saltpeter, borax, white arsenic, and fluorspar. The saltpeter referred to should be potassium nitrate, which was used also as a raw material in the fourteenth-century potash-lime glass in Boshan. According to these findings, the MgO content of the glasses made from the saltpeter was very low (below 0.5 %). “Horse-tooth stone” could be feldspar. Qing glassmaking was also influenced by western technology because some glasses contained B2O3 and As2O3, which were introduced as borax and white arsenic, respectively. The colorants included oxides of copper, iron, and cobalt. Spectral analysis showed that the red glass on the cameo samples contained a small amount (about 0.01 %) of gold. Another important innovation was the application of western technology to make gold ruby glass. This variety can be made when there is colloidal gold present in the glass batch. The red color is caused by selective light scattering of the gold particles in the glass. This process was successfully transferred from the court to Boshan by 1820 and made its way to Guangzhou (Canton), which brings up the topic of glassworks in other areas of China. Regional Glass Workshops Glassmaking in Guangzhou is thought to have commenced in the late seventeenth century. However, their art glass was not held in high repute by Chinese writers and often fell below the Qing court’s standards. Despite this, the city was an important source of skilled artisans who staffed the imperial glassworks, and records of their employment in this capacity date as early as 1708. On the local level, Guangzhou craftsmen were occupied primarily with making sheet glass for spectacles, mirrors, and windowpanes. Interestingly enough, historians in Yangzhou credit the rise of the craft in their area to the influence of Guangdong glassworkers and go on to attribute the development of a local style of trailing cameo glass to their own artisans. In common with “Peking Glass” at this time, glassmaking in either locale did not include the initial process of glass melting, but was solely the fabrication of objects from glass ingots. These ingots were known as liao qi, implying glass made with Shandong (Boshan) liao. This practice also seems to apply to a very distinctive group of wares (mainly snuff bottles) identified by the term “Yangzhou School.” According to textural references, Yunan specialized in making a type of lampshade (liaosi deng) from thin glass rods, which were widely used among the elite. The history of its glass beads is more difficult to chronicle, leaving one to suggest that, since Boshan was known to have exported glass rods to all parts of China, Yunan’s glass was fashioned from them. Glass artisans in Suzhou specialized in manufacturing glass chimes and used recycled glass for making lampshades with painted designs on the interior. Given Suzhou’s renown as a center for hard-stone carving, there is the possibility that its glassworkers also fashioned carved glass objects for the court and the general populace. As to the source for its glass material, this too, awaits further research and study. New Methods of Décor The influx of western glassmaking technology allowed Chinese craftsmen to produce art glass in a wider range of colors and employ new methods of décor. Among the latter are: • Aventurine glass – Known in Chinese as “gold star” (金星, jinxing) glass; this variety was a specialty of Venetian artisans and a particular favorite of imperial patrons. • Diamond-point engraving – The use of a diamond point to produce linear drawing on glass was introduced to the imperial glassworks in the late seventeenth/early eighteenth century • Enameled glass – In this decorative technique, a mixture of colored powered glass was allied with an oily medium and fused to a glass object in a furnace. This style of décor evolved during the Qing period. Other methods of décor which may well have been derived from European examples and glassmakers are: • Multicolor overlay – A method whereby a blank is overlaid with two or more different colored layers. • Swirled glass – This effect is achieved by gathering up small colored glass pieces onto a molten lump attached to a blowpipe and fused in a furnace. • Threaded glass – Molten colored glass in string forms is applied to a hot core to be rolled around inside the furnace for fusion, resulting in parallel segments of contrasting colors. Contemporary Glassmaking in China All imperial glassmaking had ceased in 1860. This prompted the Qing court to monopolize the nation’s glassmaking by establishing state-run companies and restricted the procurement of glass ingots from Boshan. These actions severely depressed Boshan’s economy and in 1902 thousands of its local craftsmen staged an uprising. This was suppressed and Boshans’ glass artisans were hard pressed to make a living until after the fall of the Qing dynasty (1912). Many glassmakers survived in the ensuing years by concentrating on making brightly colored wares, often in imitation of imperial pieces. The situation gradually improved and present-day China is experiencing a renaissance in its arts and crafts. Institutions such as the Shanghai Museum of Glass not only feature exhibitions of ancient and contemporary glassworks but also focus on all aspects of this art which has encouraged contemporary glass artisans to explore and expand the range of their creations. References An, J. (1991). The early glass of China. In Scientific research in early Chinese glass (pp. 5–19). Corning: The Corning Museum of Glass. Braghin, C. (Ed.). (2002). Chinese glass: Archaeological studies of the uses and social context of glass artefacts from the Warring states to the Northern song period (fifth Century B.C. to twelfth century A.D.). 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Encyclopaedia of the History of Science, Technology, and Medicine in Non-Western Cultures DOI 10.1007/978-94-007-3934-5_10183-1 # Springer Science+Business Media Dordrecht 2014