**4. Gold Leaf, Gold Leaf Gilding Technology, and Multi-Material Treatment on the Buddha's Surface**

Gold leaf is a very thin piece of gold that is produced by taking advantage of gold's ductility and malleability and then repeatedly hammering and forging it. In the middle of the 24th century BC, there was a mural depicting the production of gold leaf in the A3 chamber of the Tomb of Mereruka in Sakara, ancient Egypt (Wilson and Allen 1938, pp. 29–30). Compared with Western countries, gold leaf production technology appeared relatively late in China. The earliest gold leaf found in China was a gold-copper earring from the Adun Qiaolu site in Bozhou, Xinjiang Province, dating from the 19th century to the 17th century BCE (The Institute of Archaeology Chinese Academy of Social Sciences 2013, pp. 30–31). The re-decoration of the outer appearance of the earrings showed the precious gold, soft texture, and obvious decorative properties. With the continuous improvement of people's knowledge of metal and forging technology, gold leaf products with a larger area and higher quantity began to appear in the Middle and Late Shang Dynasties. These sites are mainly high-level tombs or sacrificial pits in Zhengzhou and Anyang, Henan Province, and Guanghan and Chengdu, Sichuan Province (Liang and Gao 1962, p. 334; Sichuan Cultural Relics Management Committee 1987, pp. 4–5; The First Team of Cultural Relics Working Team of Henan Provincial Bureau of Culture 1957, p. 72; The Institute of Archaeology of Chengdu City 2004, pp. 6–10), indicating that gold resources were mainly controlled by the upper strata of society. One of them is a semi-circular gold slice unearthed in Tomb M14 of the Gaochengtai West Site in Hebei Province during the middle period of the Shang Dynasty (c. 1700–1600 BCE) (Taixi Archaeological Team of Hebei Provincial Cultural Relics Management Office 1979, p. 43) (see Figure 7). Its thickness is only 1 mm, and the lacquerware surface is flat. Presently, this is the earliest known gilded product discovered in Chinese archaeology. In the Late Shang Dynasty, such lacquerware had also appeared in Tomb No. 171 at Anyang Da Sagong in Henan Province. Its thickness is only 0.01 mm, and the lacquerware surface is flat (Beijing Institute of Iron and Steel Engineering 1978, pp. 34–35).

**Figure 7.** Gold Leaf from the Middle Shang Dynasty. Materials: gold. Dimensions: T. 1mm. Displayed in the Hebei Provincial Institute of Cultural Heritage and Archaeology, China. Photograph taken by the author.

During the spring and autumn periods and the Warring States period (770–221 BCE), gold leaf gradually spread to the capitals of various vassal states and their surrounding areas, covering most areas of northwest, central, and north China. According to archaeological results, Chu State was the most advanced in gold leaf production in the late spring and autumn periods. Moreover, in the late spring and autumn periods of Chu (c. 1030–223 BCE), batches of thinner gold leaf were found successively in the tombs of noblemen in Xichuan, Dangyang, and Bengbu, with the thinnest being only 0.007 mm (Cheng et al. 2019, pp. 10–19; Henan Provincial Institute of Cultural Heritage and Archaeology 1991, pp. 203–208; Qin et al. 2011, p. 94) (see Figure 8). A total of 940 pieces of gold leaf with 13 shapes, including round and triangular, were unearthed in the tomb of Marquis Yi of Zeng from the early Warring States period (475–221 BCE). The thickness of the gold leaf ranges from 0.037 to 0.378 mm (Hubei Museum 1989, pp. 393–95). Each piece of gold leaf has a thick center and a thin edge. The gold leaf was used to decorate flat surfaces such as coffins, chariots, and armor. Chu State was the main gold-producing area in China in the pre-Qin period and the only vassal state that issued a gold currency (Z. Chen 2005, pp. 70–73). Gold resources and developed gold processing technology provided good conditions for the development of gold leaf products. Tracing back to its entire history, this kind of gold leaf developed rapidly from the middle and late Warring States period to the Jin Dynasty (266 CE–420 CE). It was widely applied to the surfaces of utensils and clothing made of lacquer wood, copper, iron, jade, plant fiber, etc. Moreover, it is worth mentioning that gold leaf was used exclusively by royalty. During the Sixteen Kingdoms period (304–439), Emperor Shi Hu (295–349) of the Later Zhao (319–351) produced gold fans, which had already reached the technical level of "thin pure gold such as Cicada wings" (A Record of Ye-Zhong, Lu 1937, p. 6). At the same time, Daoist external alchemy in the Northern and Southern Dynasties had also succeeded in their attempts to forge iron into gold as thin as silk (*Baopuzi Immortal Jinfen Sutra on Scroll the First Volume*, Anonymous 2016, p. 204). A large number of studies have revealed that gold leaf can be as thin as possible as long as it is stuck to the surface of something else. As a result, the development characteristics of gold leaf materialization are the key points that expand the wide applicability of gold leaf products.

**Figure 8.** Round gold leaf from the late spring and autumn periods. Materials: gold. Dimensions: D. 14.4cm. Displayed in the Bengbu Museum, Anhui Province, China. Photo source: the official website of the Bengbu Museum11.

In addition to mercury-gilded Buddha statues, the combination of gold leaf production technology and gilding technology provided another option for the surface treatment of Buddha statues. It was recorded in "A Record of Buddhist Monasteries in Luo-Yang" that people in the western regions of the city had the custom of affixing gold to the surface of gilded statues (Yang 2006, p. 210). It was believed that a patient could be cured by fixing gold leaf to a statue corresponding to the diseased part of the human body. This kind of religious behavior, which meets people's psychological expectations to a certain extent, promoted the popularity of gold leaf gilding Buddha statues. During the Northern and Southern Dynasties, when Chinese Buddhism flourished dramatically, many Buddhist believers began to use a large amount of gold to decorate Buddhist statues to display their piety. According to the existing archaeological documents, the earliest gold-covered Buddha statues made of clay, wood, and stone appeared successively in Dunhuang, Gansu Province, Mushuke, Xinjiang Province, Yungang, Shanxi Province, and other eastwardspreading routes of Buddhism during the Northern and Southern Dynasties (Lu and Wang 2013, p. 133; Z. Zhang 2006, p. 413; Zhao 2016, p. 60). During the Southern Dynasty, there were other records of foreign gold-leaf-gilded Buddha statues being brought to China, whose inscriptions indicated that they were "foreign gold-leaf seated statues" with a height of seven feet (Biography of Eminent Monks, Shi 1992, p. 179). This shows the close religious and cultural exchanges between China and foreign countries in this period. The majority of these different types of gilded Buddha statues were gold-leaf-gilded stone statues. According to statistics, there are 216 typical gilded stone statues from the Northern and Southern Dynasties in China in total. A total of 191 of them are distributed in northern China, including Hebei, Henan, Shandong, and Shaanxi provinces, while 25 are distributed in southern China, including Sichuan province (Li and Zhang 2021, p. 130). Comparatively speaking, these gilded stone statues' distribution proportion is much larger in the north than in the south. Apart from that, another remarkable discovery has drawn attention: the distribution and number of these gilded Buddha statues coincide exactly with the main route of Buddhism spreading from west to east along the Silk Road. This proves the historical fact that Buddhism was introduced into China from the west.

The gold leaf gilding technique is a type of processing technology that covers heterogeneous objects with gold leaf entirely or locally. By virtue of the adsorption of gold leaf itself or with the use of adhesive materials, the process plays a dual role of both decoration and sealing on the surface of Buddha statues. Specifically, the process can be divided into two steps. The first step is to boil the adhesive materials. Generally, a lacquer, tung oil, or icthyocolla is chosen for boiling into a thick semi-liquid, which is then evenly spread on the surface of the Buddha statue. Second, as the adhesive material dries quickly, bamboo clips are used to pick up pieces of gold leaf and place them in order. After pressing and polishing with a cotton ball or agate knife, the gilded Buddha statue is completed. Generally speaking, the face, hair ornaments, body postures, and costumes of Buddha statues are mostly uneven surfaces. In order to facilitate a consistent visual perception of gold-leaf-gilded Buddha statues, the surface adhesion of the gold leaf must be tight and uniform. Therefore, the more gold leaf produced, the thinner the thickness, the better the uniformity, and the easier it is to complete the production of gilded Buddha statues. With this background, gold leaf with an extremely thin thickness, uniform size, good uniformity, and mass production came into being. At present, there is not enough evidence to prove that these kinds of gold leaf and gold leaf gilding techniques were influenced by foreign gold-leaf-gilded Buddha statues. However, before the introduction of Buddhism to China, the main users of gold leaf gilding technology were members of royalty, which then changed to Buddhist temples. At the same time, the main objects of decoration also changed, from small artifacts to mediumand large-sized Buddhist statues, and the surface of decorative carriers changed from plane to three-dimensional.

During the Tang and Song dynasties (618–1279), when Buddhism flourished, this kind of gold leaf was widely used in large-scale Buddhist statues and temples. Emperor Jingzong (809–827) of the Tang Dynasty (618–907) built his palace with "100,000 pieces of gold leaf" (Taiping yulan, F. Li 2008, p. 203). In the Northern Song Dynasty (960–1126), the Dunhuang region's envoy to repair the Buddha statue came "begging for 100,000 pieces of gold leaf" (Song Huiyao, Edited the Manuscript, volume 198 Minority V, Xu 1957, p. 768). The gilded clay Buddha statues from the middle of the Northern Song Dynasty in Zhangzi County, Shanxi Province, are only 0.00016–0.00022 mm thick with gold leaf (Wang et al. 2020, p. 41). Built in Chongqing in the 22nd year of Shaoxing (1152) during the Southern Song Dynasty (1127–1279), the Tongnan Buddha is 18.43 m high, and 369,000 pieces of gold

leaf are used to complete the decoration of the whole body (Xu and Liao 2020, pp. 95–96). The huge demand for gold made the craftsmen look for a more economical way to use gold and a faster technique to make gold leaf. The mass production of gold leaf in ancient China was realized because of the invention and application of Wujin paper. The earliest liner material was probably made from some kind of animal hide, with paper later being made from plant fiber. It is not clear when animal skins and paper were used (Han and Ke 2007, p. 799). If paper is used as a liner material, this would indicate a time after Cai Lun (c. 61–121) developed paper from woody bast fiber in the 105 years of the Eastern Han Dynasty (Pan 1998, p. 86). In the Genealogy of Fatie Puxi of the Southern Song Dynasty, "Kui paper," which records the calligraphy of rubbing inscriptions on tablets12, is the liner paper used to make gold leaf (Cao 1939, p. 2). In the Ming Dynasty (1368–1644), "Tiangong Kaiwu" first recorded the production method of Wujin paper, stating that "all Wujin Paper was made by Suzhou and Hangzhou. Its paper is made of East China Sea bamboo film. By lighting the lamp with soybean oil, blocking the surrounding air, stopping the pinhole ventilation, and smoking light, this paper is finished (Song 1978, pp. 338–40)." Therefore, the paper has high heat resistance, wear resistance, and impact resistance. Repeated stacking helps to evenly disperse the beating force. The production of gold leaf has been upgraded from one-by-one hammering to multi-layer hammering with a uniform thickness and uniform shape13. Scholars have investigated the traditional gold leaf production process in Nanjing, Fuzhou, and Quanzhou and found that at least 1792–2048 pieces of gold leaf can be produced at one time by using Wujin paper. Up to now, Wujin paper is still the core material in gold leaf production (Lian 2002, p. 346; K. Wang 1980, pp. 40–43). The technological improvement of batch leaf production and the maturity of gold leaf gilding technology not only meet the demand for Buddhist gold but also improve the utilization rate of gold and effectively solve the construction and efficiency problems in the gold installation projects of giant Buddha statues.

In addition to the gilded decorations on three-dimensional Buddha statues, Buddhism also developed a new type of low-embossing decoration technique in the planar grotto frescoes called gelled patterning and gilding. The gelled pattern is usually higher than the wall, with gold leaf above it, in order to increase the three-dimensional stereoscopic effects of the picture. The Kizil Grottoes, in Kuqa, Xinjiang Province, were dug in the 3rd century by Qiuci State, an ancient country in the west. They are the earliest Buddhist grottoes in China and the most western in terms of geographical location. Thanks to their location at the intersection of Eastern and Western civilizations in ancient times, the cave paintings not only show the Indian and Greek styles of early Buddhist art but also have a number of traces of gilded decoration. In addition, the technique of gelled patterning and gilding can also be seen in murals from the Northern Wei Dynasty in Dunhuang Mogao Cave 263 (Duan and Fan 2006, pp. 55–59), which happen to illustrate the propagation path that Buddhism took in its spread to China from the west. In fact, whether it is a threedimensional Buddha statue or a plane fresco, the decorative layer formed by gilding on the surface plays the extra roles of waterproofing, corrosion prevention, weatherproofing, and peeling protection, which enables a lot of fragile Buddhist art that could easily decay to be preserved for a long time.
