Changsha Blue and Copper Red Wares and The Religious Motifs
By Lim Yah Chiew (Singapore)
It has been a practice in Chinese pottery culture for archaeologists to demarcate the different stages of development for a certain category of pottery ware in order to study and appreciate a specific kiln family such as the Changsha kilns of Hunan Province. Date marks are rarely stamped on ceramics during the Tang Dynasty. The Changsha wares that have been found by archaeologists ranged from 808 AD to 929 AD during the Tang and Five Dynasties period.
Changsha is rich in historical culture as it was the capital of Chu (907 AD to 951 AD). Changsha has always been a great centre rivaling the imperial capitals in the north that existed at various stages in history from the Shang and Zhou to the Han, Sui and Tang dynasties. The 1974 Han tomb excavation findings at Mahuangdui in Changsha are known throughout the world. Thus, Changsha wares are innovative in form, variety and design and are part of a vibrant cultural heritage.
Discovery of Kiln Sites and Shipwreck
The Changsha kilns of the Tang dynasty were only discovered in the middle of the last century. Based on archaeological records, Changsha wares originated and were developed from the foundations of the Yue Zhou kilns which were built prior to the Tang Dynasty in the same region. Changsha wares are characterized by under-glazed brown and green motifs and the use of paste decoration such as components with molded design in relief, appliqué designs or impressed designs in relief and also incised or carved designs. They are quite distinct from the Yue Zhou green wares which are monochrome. Thus, Changsha wares are widely accepted as a separate category of pottery ware in Chinese culture.
The recent find of the shipwreck in the seas off Belitung Island in Indonesia has yielded over fifty thousand pieces of Changsha wares on board the sunken ship named “Black Rock” or “Batu Hitam” in Malay.
In historical terms, the production of Chinese ceramics was progressively carried out in three stages of development. First, green wares were fired; followed by white wares; and finally, colored wares. The use of metal oxides such as copper and iron to form the pigmentation materials on ceramics began as early as the Tang Dynasty. The Tang Tri-color earthen wares and the Changsha wares had adopted such techniques extensively.
The copper and iron oxide were applied in the glaze material for firing to achieve the colors desired. They must be fired in oxidizing (oxygen rich) atmosphere to become green as copper oxide would turn red in reducing (oxygen deficit) atmosphere. Changsha was the only kiln that successfully produced the brown and green motifs by blending the two elements perfectly. The discovery of Changsha wares and its production of under-glazed colored ceramics marked a significant breakthrough in Chinese ceramics history.
The Findings at Motueka (New Zealand) Conservation Centre
The over fifty thousand pieces of Changsha wares salvaged from the Batu Hitam shipwreck underwent a long period of desalination and slight restoration work at the Conservation Centre in Motueka, 50 metres from Nelson, New Zealand. Most of the Changsha bowls are in perfect or mint condition as they were well preserved and kept in huge “Dusun” jars produced in Guangdong.
A total of over fifty pieces of blue Changsha wares are found at the Nelson Conservation Centre in New Zealand while about the same number of red Changsha wares are kept in storage. This fantastic find may lead us to the conclusion that another batch of Tang Blue and White pottery ware has been unveiled.
Blue and White Ceramics
Upon close examination, I believe that the above conclusion may not be correct. The chemical element of blue and white ceramics consists mainly of cobalt oxide but scientific tests carried out previously on Changsha wares proved that no cobalt oxide was ever found in Changsha glaze. The Changsha wares in the Batu Hitam shipwreck should not be an exception, especially as the blue colour has a strong turquoise tone in the glaze layer which is covered by a curious moldy hue.
Cobalt oxide has been used as a blue pigment in modern glass and ceramics industries. In ancient times, crude or refined cobalt ores were used for this purpose instead of cobalt oxide. Important examples are the early glass beads and coloured glass products made by ancient Egypt, West Asia from the period of 15th century BC to 9th century AD. It was not until the late Yuan Dynasty (14th century AD) that cobalt blue began to be extensively used as under glaze decoration in the well-known blue and white ceramics. These historic artifacts are found in important collections in many world famous museums especially those in the Middle East countries like Turkey, Iran and Iraq.
Blue and white wares of the Tang Dynasty are rare finds as the firing skill for blue and white wares was not mature then and the source of cobalt ore came from the West Asian countries, such as Persia (Iran). Up till now, the search for complete pieces of Tang blue and white wares had been futile. However, three Tang blue and white dishes were recovered from the Batu Hitam shipwreck. It provided concrete evidence that in Gongxian of Henan province, the kiln workers had already produced such wares for export to the Arabic world but the quantity produced had been so limited that such a find was very rare.
The Changsha Blue Wares
When ceramics were fired with a combination of high phosphorus and low alumina content in the copper glaze, a bluish green tone as a surface colour would be produced, which was once believed to have been caused by cobalt. This is so in the case of the Changsha wares as the ash mixture burnt from a kind of glass abundant in China was usually used to form the lime glaze, i.e. calcium oxide glaze. The ash mixture turned into a transparent glassy protective layer to the ceramic body under high temperature and it has a significant content of phosphorus oxide that justified the colouring condition for a turquoise tone.
As indicated in the historical records, the Middle East countries had a thriving trade with China during the Tang dynasty. It is interesting to see some Middle Eastern influence in the unusual opaque turquoise green ceramics ware glazes made in Changsha in the late 9th and early 10th centuries AD, particularly as these Chinese ceramics show lozenge and palmate patterns that are reminiscent of the broad and simple trailed and brushed designs used on some Mesopotamian earthen wares. In the Arabian world, lozenge or rhombus was a token of victory.
These lime rich glazes only developed into translucent turquoise blue green when over fired; yet this effect was little used by potters as lime glazes tended to run badly in excessive heat. By adding copper oxides to the milky-white emulsion glazes, blue glazes of a curious moldy hue could be produced. With enough heat, these blue glazes could show almost turquoise tones as their optical blues combined with their copper green colors. This explains why blue motif design pieces of Changsha ware are so much less compared to the ordinary green and brown pieces found so far. These blue pieces are actually “freaks”, produced through misfiring; but the rarity of such “freaks” and the beauty of these blue pieces caused them to be treasured by connoisseurs.
The existence of a milky cast in the blue glaze was a result of the firing of the milky white lime glazes which is rich in oxides of phosphorus and low in alumina, that separated in cooling into immiscible glasses. These “glass in glass” emulsion consists of minute spherules of glass within the glaze that scatter blue light. Technically, this effect is known as “liquid-liquid phase separation”, and in the case of Changsha wares, the calcium oxide will form a layer of continuous liquid plasma phase while the silica oxide or other metal content become a separable liquid inclusion phase of glassy droplets of the size average 0.08 um and are therefore considerably finer than the wavelength of blue light (0.4 – 0.5 um), but through an interference effect known as Rayleigh Scattering they produce a strong bluish cast to the Changsha ware glazes. The blue colors of Changsha glazes are therefore optical rather than true pigment effects. [Note: The blue color of the sky is caused by the scattering of sunlight off the molecules of the atmosphere. This scattering, known as Rayleigh Scattering, is more effective at short wavelengths, i.e. the blue end of the spectrum. Thus, the light scattered down to the earth at a large angle with respect to the direction of the sun’s light is predominantly in the blue end of the spectrum and the sky therefore appears blue.]
In the ceramics scientific study, the above blue glaze is a result of the yaobian or, literally, the kiln mutation effect. The yaobian glaze effect can only take place in the presence of liquid-liquid phase separation.
The yaobian effect that causes the blue color (based on the same principle as the Rayleigh Scattering effect) requires the following:
- a thick glaze layer;
- a proper heat treatment with slow cooling;
- opalescence caused by the presence of phosphorus oxide which induces liquid-liquid phase separation; and
- a correct size range of the inclusions at about the wavelength of light, or less than one micron (micrometer) in one of the two liquid phases with one rich in iron oxide and the other rich in calcium or silica oxide.
The Changsha wares would turn blue only when all the above factors are achieved, and the blue tone only appears where the glaze layer is thick. If we re-fire the blue wares to an even higher temperature, the liquid-liquid phase will merge to only one phase and the glaze will turn into a transparent and colorless layer.
Blue glaze evokes the quality of deep, cool water and such color has always had a great appeal to the Middle Eastern world. The Changsha potters were aware of this liking, and they tried hard to produce wares with the blue motifs to capture the attention of the Persian buyers. The most famous examples are the jars painted with small blue and brown dots or beads arranged in whirling circles exactly like the design of the Persian carpets. Obviously, the firing of blue motifs on the wares was done intentionally by the trial and error method through the yaobian or kiln mutation principles as mentioned above. They should be treated as treasures rather than as “freaks” as the production of it was accidental.
Changsha Copper Reds
Copper oxide and iron oxide were applied in the glaze material for firing in oxidizing (oxygen rich) atmosphere to give off the green and brown colours. However, copper oxide would turn red if put under high fire in a reducing (oxygen deficit) atmosphere. In historical terms, China only started to produce the red color effect in Jun ware made in Henan during the Song dynasty. The appearance of red patches on the bluish Jun wares was probably due to misfire, that is the dropping of copper impurities from the roof of the kiln chamber on the clay body burnt under simmering situation which enhanced the formation of reducing flame. The occurrence was rather accidental. From the discovery of Changsha wares, it seems the deliberate use of the copper red effect in Chinese ceramics first took place at the Changsha kilns in the Tang dynasty, which would bring forward the firing of copper red history to an earlier period.
The evolution of copper reds from the copper bearing Changsha green and the blue green glazes is not really surprising. Changsha wares were fired in wood burning dragon kilns built on hill slopes. The pulling effect of the wind due to the creation of a vacuum space in the firing process within the slanting structure could flare up the contents in the kiln chamber to an exceedingly high temperature in a very short while. This caused the kiln chamber to be suddenly filled with smoke, cutting down the oxygen supply and making occasional accidental reduction from the exceptionally high ash (soot) levels that would turn some of the copper oxide into cuprous oxide (red copper oxide) or colloidal copper ions, thus giving a red colour to a transparent glaze.
The Changsha copper reds were produced mainly by accident as the skill of controlling and manufacturing copper red glazes only reached their most successful expression in the early 15th century AD when Jingdezhen porcelains with copper red glazes were used in China in imperial rites. Even so, a piece of Ming copper red bowls can cost millions of dollars in the auction market. Changsha copper reds are therefore found in limited quantities and the shipwreck find will mark a new phase in ceramics history.
The under glaze paintings of birds, animals, floral sprigs and trees executed by the Changsha potters during the Tang Dynasty exhibit a good mix of Buddhist and Islamic symbols and influence. The paintings are exuberant, with attractive, eye-catching yet elegant images and produce an atmosphere of harmony of the two different religions. The majority of the designs are composed and executed in a simple, uncluttered and spontaneous manner although they sometimes suffer from exaggeration and distortion.
Brief descriptions of some of the more popular painted subjects on Changsha wares are presented as follows:
A. Buddhist symbols
Buddhism was introduced to China during the Western Han period and reached its peak in the Tang Dynasty. We have found various forms of Buddhist symbols such as the swastika sign or other familiar motifs or molded design in relief as outlined below:
- Lotus flowers: painted in exquisite style or free flow of simplified line forms. The lotus is treated as a sacred Buddhist representation.
- Sala tree (cyathea spinulosa), usually in the form of appliqué, is a living fossil of the prehistoric tree fern. The fronds are dark green and finely divided, held in a graceful arching habit, and the slender trunk is able to reach a height of about 20 feet. It was said that the Great Master Sekkiamani died between two Sala trees, and the Sala tree was regarded as a holy tree and is always shown protected in a cage-like fence.
- Makara fish, which is a legendary animal with a dragon-shaped head and curved nose, is a reincarnation of the Buddha, who always harbors the intention of tying people up for the preaching of the religion.
- Lion motif or molded in relief is a symbol of Buddhism to express the loudness and clarity of the chanting of prayers by the Buddha.Lingzhi fungus is a sign of blessing for longevity. This usually includes pictures of clouds.
B. Islamic symbols
In order to cater to the needs of the Muslims in the Middle East countries, the ingenious Changsha artisans cleverly painted motifs in line with Islamic teachings.
These consist of the following:
- Abstract geographical pictures are commonly found in Changsha bowls meant for the Arabic market. First, small dots or beads are applied at random and the beads are arranged in circles, squares and lozenges which are typical design found in Persian embroideries or carpets. Next comes the free flow lines and spiral symbols which appear as flora sprigs, foliage or even ribbons. The spiral is universally regarded as a symbol of movement. We also see festive firework patterns that exude a sense of happiness. All these abstract designs suggest that the Muslims are not allowed to worship idols or anything in the form of living creatures. Thus, the mosque is empty and only geographical patterns are drawn on the wall.
- Arabic Koran scripts written in graphic forms are found on Changsha bowls, in praise of Allah as the only god.
- Date palms are a common appliqué design especially on ewers. This is suitable for the Middle Eastern market as the date palm plantation was one of the important sources of wealth to the people then and sweet and juicy dates were a well-liked delicacy for the Arab people. The fruits of the date palm in the design have long been mistaken for that of grapes but the palm leaves are definitely different from grape vines.
The archaeological salvage of the Batu Hitam shipwreck has unlocked the secrets of the sunken ship and greatly expanded our knowledge of the Tang era. It is the oldest ship ever found in Asia, in Indonesian waters, and provides the earliest evidence of the flourishing trade between China and Middle Eastern countries via a maritime silk route. The cargo is of historical importance and can be classed as a world heritage find. The collection is a meaningful and important acquisition for Singapore as Singapore is currently an important commercial and maritime centre for the region. An exhibition of this well-preserved and stunning collection, especially the Changsha wares, at the Singapore Maritime Silk Route Museum would further enhance Singapore’s reputation as the gateway to Asia and the link between East and West. More importantly, the collection would help the government to forge closer bonds between Singapore and the Middle Eastern countries. The purchase of the Batu Hitam cargo would enable Singapore to maintain an important cultural heritage in this region. It would also contribute, in no small way, to the revitalization of Singapore’s tourism industry and help Singapore to become a world-class destination with its rich offerings of art and cultural products.
Changsha Blue and Copper Red Wares and The Religious Motifs