An exhibition of Chinese celadons, Yaozhou ceramics, from the Shang Shan Tang Collection (Hall of the Supreme Good), curated by Sabrina Rastelli, is dedicated to the Yaozhou kilns, located about 100 km north of Xi’an, in northern China. Active between the 8th and 13th centuries, this kiln revolutionised the production of celadon, becoming the most influential manufactory in the entire empire. China was the first country, in the 13th century, to create pieces with a highly refractory body coated with a layer of green glaze (in various shades), commonly known in the West as celadon and in China as qingci (stoneware with blue-green glaze). This type of ceramic was enormously popular because of its ability to mimic blue-green hues that evoke jade and the patina on ancient bronzes.
The 96 Chinese celadons on show come from one of the most comprehensive collections of Yaozhou ceramics in existence, illustrating the development of the ceramics produced by kiln. The works are exhibited in Room 12 of the Museum of Oriental Art, which in 1928, was destined to house the Chinese porcelain of what was once the collection of Henry of Bourbon. The historical setting designed by Nino Barbantini has been preserved since then and harmonizes the extraordinary Asian pieces with the character of a Rococo apartment, adorned with 18th-century mirrors and plasterwork.
By the 10th century, the Yaozhao kilns had already begun to specialise in the production of high-quality celadon (until then the prerogative of southern kilns), through a series of technological breakthroughs dictated by the need to resolve defects and drawbacks. Known later mainly for the manufacture of olive-green celadon with decorative motifs carved or impressed under the glaze, it had originally been established to produce black wares for everyday domestic use and the polychrome sancai (three-colour) ware intended mostly for funerary furnishings. Northern China was known for porcelain production and craftsmen in Yaozhou also tried their hand at making white wares (false porcelain), achieved by covering the impurities in the body clays with a layer of white slip before applying the colourless transparent glaze. The results, however, were disappointing: rather than white, the glaze was an unattractive yellow, prompting the potters to venture into the complex, and for them unfamiliar, system of firing in a reducing (oxygen-free) atmosphere.
Chemical analyses showed that the recipe for body and glaze remained unchanged, but thanks to the reducing firing, the glaze turned out a more than satisfactory green when the titanium in the slip did not interfere, making it yellowish. To overcome this problem, the Yaozhou potters began to fully glaze the objects after applying a layer white slip. However, this method presented another challenge: during firing, the glaze became a very powerful adhesive, making it necessary to limit as much as possible the points of contact of the foot rim with the bottom of the container in which it was placed for firing. Here again, the Yaozhou potters showed great ingenuity by progressively refining the technique until they devised one that left only three small scars on the base.
This practice is commonly associated with the celebrated Ru ware (produced from the end of the 11th century for a 100 years) and considered a great achievement of the Ru potters, but in fact it was their colleagues in Yaozhou, who invented it a 150 years earlier. A new challenge arose in the 11th century, when they replaced wood with coal as a fuel for firing the kilns. The different yield of coal compared to wood imposed significant changes to the layout of the kilns, while the rapid cooling at the end of the firing cycle ensured transparent glazes (as opposed to the earlier ones that were translucent). Transparency was important so that the decorative motifs executed on the body underneath could be clearly readable.
The new aesthetic taste favoured intensely ornamented objects, therefore, the Yaozhou stokers took advantage of the full maturity reached by the glazes fired in the coal-fired kilns by cooling them rapidly. As for the olive-green hue that characterizes the glaze of this period, recent chemical analyses suggest a change in the recipe, probably due to the composition of the local raw materials, characterized by an increase in the percentage of titanium, responsible for this hue.
Translucent glazes made a comeback in the late 11th and early 12th century with Ru ware, which were much appreciated by Emperor Song Huizong (r 1100-1126), who wanted them to be used at court. Once again, the Yaozhou potters were able to respond promptly to the new fashion, creating the so-called ‘moon white’ glaze, similar to jade in appearance, translucent, shiny, soft, and characterised by a very subtle shade of green (as opposed to the light blue typical of Ru pieces). In the 13th century, the Yaozhou kilns fell into decline and finally oblivion only to be rediscovered through a series of archaeological campaigns, especially in the 1990s, which demonstrated their crucial role in the development of Chinese ceramic history.
This exhibition of Chinese celadons runs until 23 October, 2023, MAOV Museum of Oriental Art, Venice, orientalevenezia.beniculturali.it