Shang white vessel - source Rosemania,
Beijing museum

Generally decorative pottery took the back seat as bronze ritual and decorative objects became increasingly important. So much so that whereas in burials in Neolithic times graves of the elite were full of pottery while those of commoners would be empty, in the Shang era, the elite would be buried with predominantly bronze pieces, pottery would appear in commoner’s graves and slave’s graves would be empty. Unglazed earthenware had reached maturity in the Shang period. Earlier black ware pottery continued and the only real change was the appearance of horizontal grooves with stamped and incised decoration between the grooves. However, there were crucial developments in ceramics in the Shang Dynasty particularly in kiln design, kaolin clays for white-bodied vessels, high-firing stoneware materials and the first high-fired glaze.

Kiln design in the Shang Dynasty had the greatest impact. The development was partly due to the metal smelting requirements of high temperatures and reducing conditions, but also based on the Northern pot kilns that were making the fine black pottery. The first step had been the separation of the pots from ash falls and contamination by placing the firebox well to one side and outside the walls of the kiln, and heating the chamber through vents in the floor. Reduction was difficult using this up-draught kiln, so it was achieved by blocking the chimney with a damper or covering the top of the kiln with a layer of earth, straw or vegetable matter and dribbling water on to this to rapidly reduce the kiln temperature with the minimum of oxygen in the atmosphere once the maturing temperature had been reached. The second step during the Shang period was a change in design that led to reduction techniques becoming predominant for Chinese stoneware and later for porcelain. It was vital to produce a downdraught kiln for reduction. The one they came up with was ingenious if a little difficult to operate. The floor of the chamber had a central vent and several vents in the outside circumference connected to the outside firebox. The circumferential vents were also connected near their tops via dampers to exhaust flues. The main chimney was at the top of the domed roof. After filling the kiln, the fire was lit and allowed to burn normally, slowly drying and warming the kiln atmosphere evenly, with all the dampers open. At the correct moment the fire was stoked rapidly and when the temperature was rising steeply the side dampers were quickly closed and the main chimney capped. The heat is forced through the central floor vent and is reflected downwards by the dome and eventually escapes via the side exhaust flues. The rapid heat rise with low oxygen content creates the required reducing atmosphere. Using these new kilns the Shang were able to consistently achieve high enough temperatures and control of firing to produce good-quality, hard-bodied, high-fired stoneware. Interestingly, no transition kilns have yet been found between this one and the “horseshoe” kiln developed later.

The white kaolinic clays used previously for slip decoration and as the body clay for the Kuei vessels in Shandong were exceptionally free of impurities, particularly iron. In the Shang period many large vessels were made from this clay. Not being very plastic, the vessels were of necessity rather thick walled, made by hand with limited use of a wheel, and had the decoration carved into the body while leather-hard. The firing temperature for the white ware was between 1050 and 1150 degrees C.

Late Shang grey tripod, cord marked
- courtesy R&G McPherson Antiques

Although kaolin is a key ingredient for porcelain, because of the composition of the body material for the white ware, its vitrification temperature would have been 1750 degrees C, well beyond reach. This white ware was exclusively for the use of the upper classes, mainly for ceremonial purposes, and used the same decorative motifs as ritual bronze vessels. Although hard and strong, it was also rather brittle and its use died out at the end of the 11^th century BC.

A more utilitarian grey or brown ware was used for the rest of the population.Surprisingly, the ceramic experts making the moulds for bronze casting were kept separate from potters, even though the latter were using the same designs and had a similar artistic environment. Increasing specialisation was becoming evident.