Yixing Clay: Sourcing Raw Materials


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Yixing Clay: Sourcing Raw Materials

Postby luca » Apr 3rd, '13, 23:21

I'm involved in a ceramic design venture for which some of the Yixing clays would seem to offer the ideal material properties for our application. Much of my information has been gleaned from one of the few books dedicated solely to purple clayware, 'Yixing Purple Clayware' by Baiquan Liang, Hong Kong, 1991, ISBN 9787501005918. There I find confirmation how Yixing zisha exhibits some of the porosity of earthenware, a low-fire clay, with the strength and durability of stoneware which is fired above earthenware tempts. These dual properties of strength and porosity may make it an ideal candidate for this product design venture. Porosity is of course what lends Yixing zisha the breathing quality valued among aficionados.

The question I'd like to pose is, how does one obtain a few kilos of authentic Yixing zisha for personal use in a ceramics studio for analysis and prototyping? Ideally acquiring some of the less refined version of zisha clay would be ideal. According to Liang, this coarser version of zisha is called 'gangsha' from which more utilitarian objects such a dragon jars for water storage were made. For gangsha, however, I suspect a trip to China would be necessary.

I am now based in Taiwan, and would like to know whether raw or some other state of Yixing zisha clay is available for shipping outside of China. The ceramics industry in Taiwan is largely centered in the town of Yingge, and perhaps it was a fluke, but in my initial exploration of the town and in conversation with potters there, it seemed that purple clay was not available for use.

I should add, that even if successful, and rather than replicating the clay body after study, actual Yixing clays were used, the amount required would be extremely minimal, the equivalent of a several dozen pots a year. No need for concern that this use of a possibly limited resource will affect the industry. According to Liang, the purple clay mined today in Huanlongshan has adequate reserves to last another 100 years and the light brown banshanlu is found in several areas with no danger of exhaustion. The red variant holds no appeal, and is another matter with regards to its supplies - Liang claims its nearing depletion if no other sources are found.

All comments greatly appreciated! Thank you.
Luca
Last edited by luca on Apr 4th, '13, 16:23, edited 2 times in total.
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Re: Yixing Clay: Sourcing Raw Materials

Postby theredbaron » Apr 3rd, '13, 23:41

As far as i am aware Yixing clay is not allowed to be exported.
Taiwanese potters have made Yixing clay pots at times though, so they must have found a way. Your best bet is to continue asking Taiwanese potters, and/or to travel to Yixing itself, and contact factories there. Which isn't a long trip from Taiwan - it's not far from Shanghai.
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Re: Yixing Clay: Sourcing Raw Materials

Postby futurebird » Apr 4th, '13, 00:24

Why not experiment to find out if we have any good rocks for teapot clay dust in any other location? There must be some other rocks...somewhere on this vast planet.

(OK not really helpful, more of a lament. )

Though I think if such rocks are in Thailand, someone would have found them by now.

I have seen "yixing rocks" on taobao ... by the kilo...could not find processed clay ...and making rocks in to clay sounds non-trivial.
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Re: Yixing Clay: Sourcing Raw Materials

Postby futurebird » Apr 4th, '13, 00:34

viewtopic.php?f=36&t=15208

This thread is excellent.
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Re: Yixing Clay: Sourcing Raw Materials

Postby Hannah » Apr 4th, '13, 01:52

That thread makes me sad :( but also makes me feel justified in spending as much money as I have on my collection so far..

Even if my tea appreciation isn't as acute as it could be yet, I'm only 22 and I will thank myself when I'm older as they get more expensive I think..

Don't know if its possible but one day I would love to go and pick out some clay myself and commission a master to make a pot for me - it's fun having dreams!!! :grin:
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Re: Yixing Clay: Sourcing Raw Materials

Postby futurebird » Apr 4th, '13, 02:34

I think it's just showing all of the easy surface clay is gone.

I'm going back to China next year (Hong Kong then by train to Shanghai.) I'm I'd really like to visit Yixing too, but I need to study more.

I'll repeat what I said about other sources of good clay-- I think it's possible. What other places have naturally colored clay with high iron content? I find it hard to believe there is only one site on earth. And frankly from the photos it looks like nature could use a break.
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Re: Yixing Clay: Sourcing Raw Materials

Postby theredbaron » Apr 4th, '13, 02:49

futurebird wrote:I think it's just showing all of the easy surface clay is gone.

I'm going back to China next year (Hong Kong then by train to Shanghai.) I'm I'd really like to visit Yixing too, but I need to study more.


Why directly? There are many nice tea places on the way to stop over and have a look - Chaozhou, Anxi, Wu Yi, etc...
I never forget my first trip to China in spring '93, taking the gambling ferry from Hongkong to Xiamen (which at the time was still a sleepy town dominated by a harbor as if from the early 1900's and lots of old shop houses with people having Gong Fu tea set ups in front of their shops, then by train i have had to wait for one week to somewhere and by bus over mostly dirt roads to the Wu Yi mountains...

...I think i am getting old... :wink:
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Re: Yixing Clay: Sourcing Raw Materials

Postby luca » Apr 4th, '13, 17:24

It's great to receive all the comments. First to address:
Why not experiment to find out if we have any good rocks for teapot clay dust in any other location?

I may go that route, but what I'm also attempting to confirm here is the uniqueness of purple clay's properties. There are a thousand varieties of clay, and some will do as replacements in the right situation, however, if Yixing were replaceable or replicable in the lab, then the value and praise of this clay as optimal for certain teas, would be somewhat unfounded. Some assert that Yixing purple clay has no other alternative which is as satisfying for tea. For my purposes, rather than tea, it's a product design venture for which the same properties that make Yixing purple clay ideal in the tea realm give it value in my intended application: the joint, often opposed properties of stoneware strength and earthenware porosity. In the world of ceramics, we do not find these two characteristics in the same natural clay body quite so effectively joined elsewhere, to my knowledge. (I am not a professional ceramacist, but have picked up a good deal of info in that area over the past few years of research).

To quote Liang:
"Clays similar to Yixing clay in colour and general appearance can be found in many parts of China and in Europe too, but they lack the sandy consistency that makes Yixing clay unique."

The sandy texture is valuable in my application, and related to other aspects of Yixing purple clay's material properties. In more detail, and related to the point on other clays in a vast world:

"[...] this clay differs from materials used in the making of other wares in China, Japan or Europe, which make look similar to zisha ware [purple clay ware] but are in fact made from different materials with different qualities. [...] Zisha clay is of the kaolin-quartz-mica type, with a high content of iron oxide. This high iron content distinguishes zisha clay from other materials of kaolin type, giving the ware its dark purplish-red color. Kaolin also gives zisha ware its good fired strength and stone-like quality, and the presence of mica in the clay body probably accounts for its rough, sandy texture. Zisha ware is fired to 1100-1200 degrees c. [...] At such high temperature most red earthenware would vitrify – that is, become hard, causing the formation of glass in the clay body and a loss of porosity. Because of the high kaolin content of zisha clay, however, when the zisha ware is fired to a temperature of 1200 degrees c it still retains a certain degree (about 2%) of porosity [...] and may be connected with the structure of the large quantity of aggregates found in zisha ware, a high proportion of which are formed from the mineral group kaolinite. Two types of pores are formed inside the clay body; the 'closed' type (in the inner structure of the aggregates) and the 'open type' (around the periphery of the particles of aggregates). When the ware is fired, these aggregates shrink and form around themselves a continuous layer of pores which give zisha clay its unique and valuable 'breathing' quality – the attribute which makes it especially suitable for making of teapots and flower pots."

At this stage, its seems zisha is indeed unique, but that may be overturned with further research and experimentation in the lab and studio. The first step is to obtain the material!
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Re: Yixing Clay: Sourcing Raw Materials

Postby bagua7 » Apr 4th, '13, 19:10

luca wrote:At this stage, its seems zisha is indeed unique, but that may be overturned with further research and experimentation in the lab and studio. The first step is to obtain the material!


Very unwise, in my opinion. By doing so you'll be creating/manipulating an already natural product (clay) and tampering its inherent Qi nature (Earth, Kun trigram in the Pre-Heaven Bagua) and when manufactured it will yield a very inferior product.
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Re: Yixing Clay: Sourcing Raw Materials

Postby edkrueger » Apr 4th, '13, 19:47

It will be OK if the clay is red though... or maybe just tie a red ribbon around it.

You do realize that clay isn't simply dug out of the earth and made into teapots?
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Re: Yixing Clay: Sourcing Raw Materials

Postby luca » Apr 4th, '13, 20:27

As regards the previous two comments - I'm referring to analyzing zisha and replicating some of its desired qualities in a NEW body from other materials with a ceramics engineer, basically building a clay body from other individual elements, and not necessarily using a naturally occurring clay. The intended use of the material, again, has nothing to do with the manufacturing of pots.

And yes, fully aware the clay is not simply "dug out of the ground" and tossed on a potter's wheel. I assumed that might be clear from the depth of the above and reference to previous years researching ceramics. Yixing zisha, like most clays, is filtered multiple times and manipulated in various ways to reach the state where it can be handled in the potter's studio.
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Re: Yixing Clay: Sourcing Raw Materials

Postby futurebird » Apr 4th, '13, 20:42

I'm looking forward to whatever you find. Have you found a clay with a similar level of stiffness so you could at least practice the build techniques?
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Re: Yixing Clay: Sourcing Raw Materials

Postby luca » Apr 4th, '13, 20:51

Stiffness alone is only one attribute and any porcelain, which is fired still higher than stoneware, will exceed the stiffness of Yixing stoneware and all earthenwares. It is the combination of relatively high stiffness for stoneware, plus the porosity and aggregates, and the sandy texture, all together that holds a special appeal, not high compression strength alone. Porcelain and all other stonewares encountered to date, are too vitrified, whereas Yixing zisha retains some its porosity after firing despite the fact that other stonewares become vitrified.

In short, no, another clay with all these properties has not been found. We have strength is some, and porosity in others, but either characteristic alone excludes the other, generally. Prototyping has been ongoing for quite some time and initially involved other materials before exploring the ceramics path, such as polymers, metals, mineral-filled polymers, glass, terracotta, etc... It is merely a coincidence of sorts, a fluke, that this famous clay appears to fit the bill; the initial interest was not due to its reputation and value among tea aficionados.
Last edited by luca on Apr 5th, '13, 10:59, edited 2 times in total.
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Re: Yixing Clay: Sourcing Raw Materials

Postby edkrueger » Apr 4th, '13, 21:05

luca wrote:As regards the previous two comments - I'm referring to analyzing zisha and replicating some of its desired qualities in a NEW body from other materials with a ceramics engineer, basically building a clay body from other individual elements, and not necessarily using a naturally occurring clay. The intended use of the material, again, has nothing to do with the manufacturing of pots.

And yes, fully aware the clay is not simply "dug out of the ground" and tossed on a potter's wheel. I assumed that might be clear from the depth of the above and reference to previous years researching ceramics. Yixing zisha, like most clays, is filtered multiple times and manipulated in various ways to reach the state where it can be handled in the potter's studio.


I was being sarcastic in the first part and the second comment wasn't directed at you. I assumed that you might have noticed that Bagua claimed that processing clay did some mumbo jumbo that made an inferior product. I was wondering if he realized that most clay is processed.
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Re: Yixing Clay: Sourcing Raw Materials

Postby bagua7 » Apr 5th, '13, 02:11

What I meant was processing clay the same way you process food and turn it into a completely denatured product.

Remove Yixing pottery from Taoist principles and you'll soon find out how good your Tai Chi Chuan or Bagua Quan is. An empty art with no spirit.
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