Yixing is a city in the Jiangsu region of China. The raw materials of Yixing clay are dug very deep underground, sometimes under heavy rocks of sedimentary deposits. Once excavated, they are usually located in layered layers of other clays. The thickness of a layer of Yixing zisha ranges from several decimetres to one meter. Yixing clay consists of mud containing metals, mica, kaolinite and a variable amount of quartz and iron as the main mineral constituents.

The treatment of the clay begins with drying in the open air, then the dried clay is sprayed into fine pieces. The clay powder is then passed through a sieve, then mixed with water until a paste is obtained, stacked in a heap and treated to evacuate the air bubbles. The quality and quantity of water in the clay determines the quality of the finished products. After these procedures, the clay is ready for use.

The Yixing clay undergoes a small shrinkage during cooking, and produces objects of very good resistance. The appearance of Yixing products, such as color and texture, can be changed by artisans by adding different oxidizing metals to the clay.

Yixing clay Yixing clay teapot

Yixing clay is a kind of sandstone clay produced in the region of the city of Yixing in the province of Jiangsu in China, from which small objects of red or brown color, generally unvarnished, are formed. The clay used for Yixing objects has a very good texture and can be modeled very easily, from heaps, patties, but also with throwing. The most famous objects made with Yixing clay are the teapots (Yixing hú), which are considered the best in China and are essential for gongfu cha (the art of tea).

Types

The terms “Yixing clay”, and also “Zisha clay”, are often used to refer to three types of sandstone:

Zishaou zini (literally “purple clay sand”): a dark brown sandstone which gives its name to the type of Yixing sandstone.
Zhuni (literally, “cinnabar clay”): a brick red sandstone which gives a clay containing a high level of iron. The name only refers to the sometimes bright red color of cinnabar (pinyin: zhūshā) and does not contain the mineral itself. There are currently 10 mines producing it. However, due to the constant increase in demand for Yixing stoneware, zhuni is only available in small quantities, and its quality is said to be declining. Zhuni should not be confused with hongni (literally, “red clay”, a red clay of inferior quality. Although similar in color with zhuni, hongni does not have the same physical properties as zhuni. Most hongni is industrial which is used to mass produce of lower quality.
Duanni (literally, “fortified clay”): sandstone containing microminerals such as zini or zhuni clay; the result is varied textures and colors: beige, blue, green to black.

It is possible to find many objects that do not come from these types of earth. The industrialization of the making of pots or teapots, and trade outside the region have opened the door to practices of adding minerals or other substances and mixing clay.

Production

The raw materials for Yixing clay are dug very deep underground, sometimes under rocks heavy with sedimentary deposits. Once excavated, it is usually located in layered layers of other clays. The thickness of a layer of Zisha Yixing ranges from several decimetres to one meter. Yixing clay consists of mud containing metals, mica, kaolinite and a variable amount of quartz and iron as the main mineral constituents.

The treatment of the clay begins with drying in the open air, then the dried clay is sprayed into fine pieces. The clay powder is then passed through a sieve, then mixed with water until a paste is obtained, stacked in a heap and treated to evacuate the air bubbles. The quality and quantity of water in the clay determines the quality of the finished products. After these procedures, the clay is ready for use.

The Yixing clay undergoes a small shrinkage during cooking, and produces objects of very good resistance. The appearance of Yixing products, such as color and texture, can be changed by artisans by adding different oxidizing metals to the clay.

The potters of Yixing have been able to adapt to the threads of the centuries at the request of foreign merchants, whether they come from Asia (Thailand, Korea or Japan) or Europe (mainly from Holland, England and France) and this from the 17th century and even more so in the 18th century. In some cases, these artisans have created shapes and models specifically adapted to their customers; this is how a large production was exported to Europe during much of the 18th century (Source: Patrice Valfré, Yixing, teapots for Europe, Éditions Exotic-Line, 2000)

The traditional and artisanal manufacture of Yixing clay teapots is on the list of Intangible Cultural Heritage of Chinese Humanity. Knowing that high-end teapots can reach up to 1 million euros.