Celadon is known as a kind of ceramic with a colour glaze. Such coating is achieved by applying a liquified clay slip recipe to the ceramic ware before high temperature firing. In this article, we’ll look at when ‘true celadon‘ was invented and the conditions that let to its rise.
Primitive Celadon, Shang Dynasty
The history of ceramics in China is a long one. As early as 5000 years ago, white pottery made from kaolin clay already existed in China, which was the base material for celadon ware. However, it wasn’t until the Shang dynasty (1600 – 1046 BC), glazed wares close to celadon gradually appeared.
As the firing process was still somewhat primitive, the glazed layer wasn’t strong and durable. We therefore call this: ‘primitive celadon‘.
True Celadon, Eastern Han
By the Eastern Han Dynasty (25-220), the conditions for firing ‘true celadon‘ were in place thanks to the long-term accumulation of experience, resulting in:
- Improved in the selection of raw materials and glazing techniques
- The upgrading of the dragon kiln structure, resulting in increased firing temperatures and better control of the firing atmosphere.
Hence, this let to the rise of mature celadon ware. As ceramists could choose from a wider range of raw material and vary in firing temperatures, this resulted in a wider range of possibilities and colour of glazing.
The ancient celadon glaze colours of excavated items have a different glaze colour compared to when they were just made. Due to ‘secondary oxidation’ the glaze turned brownish. See for example the celadon basin from the Eastern Han Dynasty below:
Case in Point: Black Glazed Celadon
The innovations discussed also let to the rise of black-glazed celadon. Before the conditions were right, ceramists tried for decades to achieve black celadon, but left only to be disappointed with a greyish result. Due to innovation in raw material, ceramists increased the iron content in the glaze, while applying higher firing temperatures. This resulted in a perfectly smooth black surface.
Basic Conditions for Firing True Celadon
The successful firing of Eastern Han celadon porcelain is a major achievement in the history of ceramics and an essential leap forward. This couldn’t be achieved without the following three basic conditions, which we will now discuss more in detail.
1. The selection of raw materials for celadon making
Celadon mica is the main raw material for making celadon ware. It’s a mixture of sericite and quartz, equivalent to a mixture of kaolin, feldspar and quartz. It contains less organic material, is less viscous and less absorptive, and is mixed with hydromica-based minerals. It has a high iron content, making it suitable for ‘firing with a reduction flame’, not allowing oxygen to interact with the glazes.
Many areas in Zhejiang province are rich such raw material. It is not surprising that the first more mature celadon-glazed porcelain first appeared in Shangyu, Zhejiang Province. This was followed later by Ningbo-Shaoxing plain’s Yue celadon and Dayao village’s Longquan celadon, which are both also located in Zhejiang province.
2. The making of high-temperature resistant glazes
At the same time as the invention of lime glaze in the Shang dynasty, the method of brushing glaze on pottery had already been mastered. But because the initial glaze making process was not yet mature, and the glaze method was simple, so the glaze layer was very thin and uneven, and could crack easily during the firing process.
By the Han dynasty, the glaze dipping method appeared. This made the body and the glaze bond firmly, and made the glaze thicker and more transparent.
Control of kiln chamber temperature
On the basis of the better selection and production of raw materials, the dragon kiln of the Eastern Han Dynasty was also improved, which created external conditions for the firing of porcelain. The clay must be at least 1100°C before it can be fully celadon.
The results of laboratory tests on Eastern Han celadon indicates that the firing temperature exceeded 1200°C.
An Early Piece of Eastern Han Celadon
Let us take a look at this Eastern Han dynasty celadon-glazed porcelain jug. It is 24.5cm high, 11.5cm in the diameter of its mouth and 9cm in the diameter of its base. The jug is covered with celadon glaze both inside and outside the body, except for the outer bottom. The neck and shoulders are incised with water-wave motifs, and the abdomen is incised with a dense string pattern.
The original celadon glaze turned brownish due to secondary oxidation, yet we can still see that the glaze is even in colour and thickness, without cracks.
Although this piece still falls short of mature porcelain, it is a much more advanced version of primitive porcelain, and is one of the earliest porcelain pieces found in China.
After the end of the Han, celadon ware produces during the Six Dynasties period (220-589) kilns were established in Ningbo-Shaoxing region in Zhejiang province. These kilns produced celadon known as Yue ware.
Yue ware is characterised by elegant shapes, restrain in decoration, grey-greenish muted colours, and thin glazing. It was generally fired at a temperature above 1300ºC. See below an early Yue ware piece.
The production of Longquan celadon started around the year 950. Early Longquan ware were yellow-green or olive-green in colour.
Longquan ware got a boost in production when the capital of China was moved to Hangzhou druing the Northern Song (960–1127), which is near Longquan production area.
It became really popular around the Southern Song period (1127-1279), when the first Longquan celadon pieces were made in the iconic sea green colour. Quality improved significantly during this period.
The area were Longquan was produced, is also one of the largest historical ceramic making areas in China. Archeologists have found around 500 kilns in that region. For hundreds of years celadon was an important export product.
Celadon started to lose popularity when blue and white porcelain from Jingdezhen started to rise in popularity during the 14th century.