Introduction
Compared to my previous article about the Traditional Yixing Zisha Processing, this one was much more complicated to write and understand. It took me 9 months to finish this series. However, after lots of research, I think I now understand most of the Yixing Clay Processing Methods. If you have questions or something you don’t understand, then feel free to leave a comment.
And without further Ado let’s get into it…
Modern Yixing Zisha Processing
There are three things that make Yixing Zisha Pottery unique in the world. The Material, The Processing, and the sophisticated way the teapots are made. Previously I wrote about the Main types of Raw ore which is used in Yixing Zisha (you can read it [HERE] ). The main and original material which was Traditionally used is Zini (You can read more about Zini [HERE] ), but the following processing method can be applied to other kinds of Zisha too, with the exception of Zhuni. I’ll explain each step in detail, but you can use this flow chart as a cheat sheet whenever you wonder about how Modern Zisha Processing is done.
I got most of the pictures from [THIS] video and sites I came across during my research. The Modern Zisha Processing method is much more complicated and contains more steps than the traditional one. However, it is mostly mechanized and has a much larger throughput. Hundreds of kilos of clay can be processed this way on a daily basis, so 99% of Yixing Teapots on the market are made of Modern Zisha Clay, incorporating many of the modern processing steps.
1. Material Selection — 选料 — Xuǎn liào
Selecting The raw materials is the first step in making a good teapot. The potter has to decide what kind of teapot he wants to make, what should be the color and the overall look of the finished work. The Meticulous selection of very specific ore types will be reflected much more on the finished teapot than just sorting the ore by the main categories of Zini, Hongni, or Tuanni.
In ancient times not much effort was made to sort the raw Zisha ores. Only Masters of the time took the effort to make their own clay recipes. This is how the famous legendary Zisha clays came to existence, such as Tianqingni, Dahongpao, Lipini, etc.
During the Material selection, larger impurities are removed from the ores. However, impurities can be embedded in the ore itself. That’s why there is a need for weathering, which is the second step in the processing of Zisha clay.
2. Weathering — 风化 — Fēng huà
After the ore materials are selected they are piled up outside and exposed to the elements. The constant raining, wind, sun exposure makes the ore absorb moisture which results in cracking and the ore getting loose. Usually weathering is done during the summer or winter, because the weather during that time is optimal for breaking down Zisha ore.
Because Zhuni is soluble in water it doesn’t go through a weathering process, as the ore would be just washed away and nothing would be left of it. Instead, they let Zhuni age for a longer time. In the Modern Zisha Processing method, weathering can be skipped, if the Raymond Mill is used during the crushing process.
3. Crushing — 粉碎 — Fěn suì
In order to make Zisha clay, they need to make a powder out of the weathered ore. The size of the particles is generally referred to as the mesh size (目). A smaller mesh number (30目) gives the pot a rougher look and feels, more texture, while a larger mesh number (80目) results in a smooth surface.
Nowadays they use two kinds of mills. Either a motorized version of the old stone mill, which produces a very similar result to the hand-operated version (used for higher quality clay), or modern milling equipment (Raymond Mills), for lower quality mass production.
The Raymond Mills (雷蒙机) can grind the ore down to any size between 60 – 325 Mesh (目) and can produce 3+ tonnes of ore an hour. However, because of the large production volume and heavy use, many fine iron particles can be mixed into the ore powder, which has to be filtered out in later steps. Another downside of the crushing machines is that they produce too uniform, fine particles, which can lead to particles forming less porous clusters, resulting in uneven porousness in the teapot’s body.
4. Sieving — 筛分 — Shāi fēn
Sieving is done to ensure uniform particle size of the ore dust. If Raymond Mills were used to crush the ore, then this step can be skipped. Otherwise, they use motorized, shaking sieves to decrease costs.
During the Ming and Early Qing Dynasty, the Mesh size was between 26-35, while at the end of the Qing Dynasty, the Mesh size increased to 55-60 Mesh, showing that the general preference shifted towards teapots with a smoother, more refined look. In the Factory 1 years and modern times, with the advancement of technology, the general mesh size further increased to the 60 – 120 Mesh range.
5. Purification — 提纯 — Tí chún
After the ore dust has reached the desired size, it has to go through further purification and filtering. At this stage of the processing, most of the remaining impurities are iron and other mineral-based particles, such as biotite, amphibolite, magnetite, limonite, siderite, pyrite, etc.
Iron-based particles are especially troublesome as they can result in very noticeable “faults” on the teapot’s surface, such as black dots and small holes. Therefore in the modern days, they introduced natural and chemical cleansing methods.
( It’s worth mentioning that in the traditional process, no filtration was done at this point of the process )
A natural, but expensive way of cleansing is using strong magnets to remove ferromagnetic iron particles from the clay. The ore dust is run through magnets when it’s dry and stirred with strong magnets when the dust is mixed with water. However, this purification method is not perfect, while being expensive, so for cheap teapots, the chemical process is used.
In the chemical cleansing method, they add Hydrochloric Acid (HCL) or Sulfuric Acid (H2So4) into the water. This method removes all impurities from the clay. However, it also destroys its structure and unique attributes which makes Yixing Zisha special.
6. Mixing with Water — 水拌 — Shuǐ bàn
After the ore is purified, it is mixed with clean water. This is the stage when they add most chemicals into the clay. Such as Barium Carbonate, Waterglass, certain coloring oxides, and the aforementioned chemical cleansers. After the soup is “spiced up” they leave it in the water until it reaches the desired plasticity.
7. Mud Training (I) — 练泥 — Liàn ní
After they drained the water and reached the desired texture, they put the wet mud into the vacuum machine.
It compresses the mud and removes most of the air and water from the clay body. It’ll be formed into cylindrical tubes or cuboid blocks, and cut into 50 cm long parts. Usually, they do about 3-4 rounds of Vacuum machine mud training, to reach the desired density. The clay structure will be much more uniform and eliminates the error of bad manual mud training technique.
Using this modern method, the shrinkage and chance of deformation of the pot body is increased. However, it can be circumvented with more precise and controlled firing.
8. Aging — 陈腐 — Chén fǔ
Thanks to the use of the vacuum machine the clay doesn’t have to age as long as after the Traditional Mud Training, so most clays are ready to be used after 3 – 6 months. It’s left for aging to increase the plasticity of the clay. This will help during the building of the teapot and the firing. During aging organic matter in the clay bodies degrades and dissolved salts come to the surface. After the clay reached its desired plasticity there is no point to age it further, as it doesn’t affect the way the teapot brews tea.
“Thanks” to the addition of Barium Carbonate during the water mixing process, the clay can be stored for about 10-15 years and used anytime, without getting Flower Glaze (封釉 — efflorescence). However, after that Barium has to be added again, or do Manual Mud Training on the clay before using it.
Source:
- Video where most of the pictures came from can be found [HERE]
- During my research, I visit various sites and see what statements are consistent among all of them, so here I won’t list all 50+ sites I visited, but just the ones, which are the most detailed and helped me reach a conclusion
- Yixing Zisha Mineral by Zhu Zewei – 宜兴紫砂矿料 by 朱泽伟
- https://www.zisha.com/knowledge/23739.shtml
- https://mp.weixin.qq.com/s/DVCPQ-CmWhVtgZUzOTUCDg
- https://zhuanlan.zhihu.com/p/39331809
- http://kuaibao.qq.com/s/20191130AZP6Q800
- https://zhuanlan.zhihu.com/p/67428956
- https://www.jianshu.com/p/c818133556d2
- https://tieba.baidu.com/p/6666756884