Editorial Conversation: Chapter 9, Section 6: Historical Experiments in Yixing Construction - Slip Casting Yixing Teapots
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[00:00:00] Jason Cohen: Hello everyone. I'm Jason Cohen, the author of An Introduction to the Art and Science of Chinese Tea Ceremony. Today we're discussing Book 2, Chapter 9, Section 6, Historical Experiments in Yixing Construction, Part One, Slip Casting Yixing Clay. Here to talk about this chapter is our editorial team, Patrick Penny.
[00:00:23] Pat Penny: Hey, hey.
[00:00:23] Jason Cohen: And Zongjun Li.
[00:00:25] Zongjun Li: Hello.
[00:00:27] Jason Cohen: This chapter contains a note, a warning for practitioners not to use slip cast Yixing teapots. Why is that, and how can they identify a slip cast Yixing teapot?
[00:00:37] Pat Penny: The easy answer on why, they break, they crack, they're very prone to cracking. And it would be particularly sad if you had an example of one of these, which is generally going to be from, what were the years, the late 50s? Is that correct? It'd be sad if you had a 70 year old teapot and it was no longer intact because you decided to brew tea with it.
[00:00:58] Zongjun Li: Yeah, and also the ultrafine clay particles made the surface really shiny and smooth. With some addition of feldspar and other materials, it really drastically increase the vitrification rate of the teapot. So it has a glassy texture.
[00:01:16] Jason Cohen: Is that the only identifying attribute or quality, or is there some other way someone looking at a Yixing that they find could know that it's a slip cast Yixing teapot?
[00:01:27] Pat Penny: They often have a lot of tool marks in them so trying to remove the Yixing material from this mold would often cause there to be tool marks that are unable to be removed through ming zhen (明针) because the surface of the material is already so smooth that ming zhen (明针) wasn't able to often be properly applied so you'll see a lot of small indentations or imperfections because it's not able to be smoothed away.
[00:01:50] Zongjun Li: Yeah, so you are basically using a ming zhen (明针) tool to scrape away all the imperfection on the surface. And a slip cast ware is usually very prone to deformation because it's really soft. It doesn't really have the kind of similar structural integration comparing to the normal zisha ware.
[00:02:11] Jason Cohen: Are there any other identifying attributes?
Particularly, I'm thinking about artifacts left by the mold itself, something that separates it from either a poorly built, low level craftsman, an early production by apprentice versus something that is a telltale sign of it being slip cast.
Zongjun, you had mentioned the vitrification rate, the glassy surface, but is there something that's left by the mold itself that we could use as an identifying attribute?
[00:02:39] Pat Penny: Often with the slurry casted teapots, it would just be the body that was usually built by it. So I think you'd see clearly that all the other attached pieces, like potentially the lid knob, spout, the handle, these would clearly be a different texture because they would be hand built, so I think just the juxtaposition of the teapot body versus all the other components having that drastic difference would be another sign.
[00:03:03] Jason Cohen: That is definitely true. The one other attribute that will frequently identify it is a seam line, a thin but present seam line across the body, down the center line. That's where the two pieces of the mold fit together and connected together and they were unable to smooth that with ming zhen (明针).
[00:03:20] Zongjun Li: Yeah. A lot of the plastic wares use similar technology too.
[00:03:26] Jason Cohen: What is slip casting? What are slurry molds, and how do they work?
[00:03:31] Zongjun Li: One good imagination of a slurry mold is basically when you're trying to cook a very thick soup in a giant pot, and you pour the soup out, but you still have some leftover in the pot. And as the pot is still being heated, and as the soup inside the pot is slowly getting dehydrating, you end up having this layer of crust sitting inside the surface of the pot. And that's basically the mechanism of how people make slurry mold wares.
Dump a giant jug of slurry clay into a mold, and you pour a very specific quantity out from the slurry mold, leaving a layer of crust inside the slurry mold and let it dry. So the quantity of you pouring out from the mold and the time of you letting the slurry to dry inside the mold will determine the thickness of the ware.
[00:04:26] Jason Cohen: Pat, do you want to use a different metaphor?
[00:04:28] Pat Penny: I've got so many great metaphors for this. Just the simplest one is just thinking of the molds themselves. So we talked about other tools and mold shape guides in the previous chapter so you could really just think about it as a piece of plaster or cement but it's just a strong and solid shape that has been carved away into some other material. And as you add this slurry, which is water and ultrafine clay particles mixed together, often with some agents to make sure that the clay particles aren't settling out, as you add that material in, it is able to basically form the negative like a photo right, almost the negative of the shape that the mold is cast into.
And the material for the mold needs to also be able to transmit water through it. So as the clay releases water through the mold, you eventually have it drying out, that slurry clay drying out, and you'll be able to at some point separate it from the mold. Although as we mentioned, it's not without some markings or deformation upon it.
[00:05:30] Jason Cohen: Just to clarify Zongjun's metaphor, the ware itself, the slurry clay inside the mold is not heated. The water is sucked out through the porous, technically micro porous structure of the plaster mold, leaving behind a thin layer of clay, which is then extracted, which is then jointed, which is then dried and fired in the standard methodology.
[00:05:54] Zongjun Li: That's right. It's unfortunately not clay soup.
[00:05:58] Jason Cohen: Not a true soup.
[00:06:00] Pat Penny: Not yet, but you know the future is still ours to shape.
[00:06:05] Jason Cohen: To mold, Pat, to mold.
[00:06:07] Pat Penny: No comment.
[00:06:08] Jason Cohen: Is this an accepted technique? Are there high quality wares made via slip casting?
[00:06:13] Pat Penny: Not for Yixing teaware.
[00:06:15] Jason Cohen: But for other ware? Is any high quality wares made from slip casting or do we consider this to be a low skill or low end technique?
[00:06:23] Zongjun Li: Some of the porcelain wares are actually made by slip casting and they are doing perfectly fine.
[00:06:30] Jason Cohen: Some of the good porcelain wares or any porcelain wares, imperial porcelain wares, Jingdezhen? What level should we consider this as a skill set, as a technique, as a methodology, or should we just bucket it as it didn't work in Yixing and it's not a good method?
[00:06:46] Zongjun Li: To my knowledge a handful of late Qing, Jingdezhen wares and also some of the higher quality European porcelain wares at the time are made out of such methodology and they present pretty good results.
[00:07:00] Jason Cohen: Why is that? What is the difference? Is it that Yixing is a different material?Is it that Yixing is unglazed? Is it a combination of these things? Why can slip casting work with other materials, but not with Yixing?
[00:07:13] Zongjun Li: Porcelain wares are glazed and it's really the glaze that's the contact surface to the tea versus Yixing is the clay itself.
So in that sense, such a comparison is not fair. Because, you are essentially comparing two different material.
[00:07:30] Pat Penny: Right, and the slurry material you need to make is going to have very different properties both pre and post firing than the hand built Yixing teapots.
We're going to see really different interaction with the tea because of the way that the material is prepared.
[00:07:46] Jason Cohen: Maybe even shards, if we heed the warnings.
[00:07:49] Pat Penny: Very true. So we're not supposed to be making tea with these slurry mill teapots. Beyond just the physical interaction, as we've talked about already at length, the appearance of these pots also present some deficits compared to the hand built products because of the Yixing material itself.
[00:08:07] Jason Cohen: If slip casting resulted in such low quality or low utility wares with zisha clay, why did Yixing Factory 1 implement the method?
[00:08:14] Zongjun Li: Efficiency, for sure, in the very first place. When F1 trying to increase their production and lower the cost, you can do a lot of mass production with such technique. But then they quickly found out that a lot of the parts do require the human touch, and the quality is really not up to the standard.
[00:08:34] Pat Penny: And part of it was the labor resources they had as well. You had some people who probably early on in the F1 days did know how to work Yixing teapot material. But I'm sure you had many other people who were part of the collective labor force who were not experts by any means in making Yixing materials. So this was a way to hopefully use their labor more efficiently. But as we saw moving to the future, it did not become the standard methodology.
[00:08:59] Jason Cohen: Were there any other factors at play, particularly political or ideological factors?
[00:09:04] Pat Penny: The application of slip casting to at least teapot construction was an imported ideology. While there's some evidence, I think you've mentioned in the book of slip casting in China previously, I think we didn't see it being implemented at least in the clay ware tea industry.
So, it was technology that was in some ways being imported from some European countries with their porcelain ware production. So it might be that the Chinese Communist Party saw this potentially as something that was not Chinese in origin, which politically there may have been reasons to double down on traditional hand building methodologies as this failed.
[00:09:41] Jason Cohen: Or potentially the opposite. They saw this as imported technology, which was needed to leapfrog the current level of technological abilities and turn a craft into industry. Do you think that it was the Yixing ceramic craftsmen and artists themselves who potentially were ideologically biased against the imported technology into the art form?
Or do you think that the government would have been for or against it?
[00:10:09] Zongjun Li: At the time, any kind of importation and implementation of knowledge was very top down, like individual artists under the organization would not really have any opinions or sayings in making any decisions.
I would say that it's probably from a very top down management that doesn't really know what Yixing production should be, or can be, and saw this opportunity of increase production quantity And just start implementing the technology, without a lot of conversation or a lot of hands down experiment with real artists or real production.
And later on, abandoning such technology I think was definitely from bottom up. It's definitely feedback from actual artists making the production telling the management that this is not going to have results that live up to the standard.
This is most likely the interaction between the decision makers and actual artists.
[00:11:12] Jason Cohen: How did that failure of slip casting shape the view of technology by craftsmen in Yixing going forward?
[00:11:20] Zongjun Li: They really start to putting up a question mark on a lot of the technology that they trying to implement or a lot of the traditional technology or at the time outdated technology that they trying to give up. Like, for example milling Yixing ore into powder. Traditionally you use stone mill for milling.
And later on, people start to implement Raymond Mill, which is a metal ball mill to mill Yixing ore into powder, which result into a very spherical shape Yixing clay that doesn't necessarily play well with water and with Yixing construction. The deformation rate is significantly higher.
So right now, people are trying to use stone mill for better quality teapot construction in Yixing versus using more efficient machinery.
[00:12:12] Pat Penny: I would agree that the Yixing craftsmen have stuck to tradition maybe through some of these experiences, their predecessors having failure with adapting new technologies, but I think we do still see Yixing artisans today who are open to new innovations or new technologies but I think they weigh them very carefully and are very methodical about testing them against the performance of some of these traditional methodologies.
[00:12:36] Zongjun Li: That's right. That's right. It's not like they're trying to just abandon modernization, right? We see all these clay extrusion machine in Yixing town that's very widely used. And I think people doesn't really necessarily have any problem with that.
[00:12:52] Jason Cohen: What is the linkage between slip casting and shape guides?
[00:12:57] Pat Penny: Many of the plaster molds that were used for slip casting, pouring slurry into, when used with non slurry clay basically, you can take the clay, press them into those shapes to still get proper guides. So I think the application of the plaster molds themselves is perfectly fine, as long as the slurry going into it is not a material like we see being used in the 50s to 60s slip casting.
[00:13:25] Jason Cohen: And yet, those original plaster slurry molds becoming guides, is that not a form of new technology or imported technology? Should we view it this way or should we view it as something else?
[00:13:38] Pat Penny: I think it's an adaptation of the technology to best fit the art forms. As we were just saying, the Yixing craftsmen, they certainly do innovate. And I think this is a form of innovation where it did increase the efficiency of building these teapots. You didn't need maybe quite the same level of skill because you could use the plaster mold to at least help with the shaping. Particularly, when we're talking about the ROC period, F1 period but, you know, nowadays, as we had mentioned in the last chapter, we don't look at there being anything wrong with a half hand built teapot, leveraging these shape molds.
[00:14:10] Zongjun Li: Yeah, I think the key difference is that what's going into a shape guide is Yixing clay, and what's going into a slurry mode is slurry, like the material, it's it's different and the result is different.
[00:14:25] Jason Cohen: That is a great way to put it. My last question, was there any way in which the slip casting method was successful?
[00:14:34] Zongjun Li: Porcelain, maybe?
[00:14:36] Jason Cohen: No, in Yixing.
[00:14:37] Zongjun Li: In Yixing?
[00:14:39] Pat Penny: The production of shape guides that's one legacy of slip casting that is positive. You can use slip casting for commodity wares. So if you want not great, not Yixing teapots, so teapots made of other material that it gets sold online as Yixing teapots.
[00:14:56] Zongjun Li: Or other things, like flower pots, made by jiani (甲泥).
[00:15:00] Jason Cohen: It protects the low end of the market, it protects Yixing from the low end of the market.
It's a difficult question. I found that this chapter was more interesting to write than I expected it to be, particularly with the three sections on its history and its legacy. On the other hand, I do have difficulty answering this question. Is there any way in which it is successful?
I think the legacy of leaving behind more consistent shape guides helped inform F1's production methodology and particularly its ability to train many ceramic artists, ceramic craftsmen, to become ceramic artists.
And, as we were just saying, the idea that the failure of slip casting in Yixing reinforced how different the art of Yixing is both being an ore that's processed into clay, a very difficult clay to work with, a clay with unique property, is a clay that is not glazed, which means you can't hide any surface defects and it reinforces idioculture of Yixing craft as its own art form separate from the perhaps larger arc of ceramics.
And potentially the failure of slip casting led to the preservation of many of the techniques and much of the skepticism of modernizing techniques such as ball mills or such as clay dyes or such as added colorant compounds that still pervade the top end of the market.
It's hard to say exactly what was successful about slurry molds, but I find them to be an important and interesting part of Yixing history.
[00:16:45] Zongjun Li: Yeah, I think it's one of those really inevitable experiment that happens during the period. Not only you see that in Yixing production, but also tea production, like production of trying to artificially accelerate the aging process of pu'er. Luckily on that end we end up having shou pu'er. It's not totally garbage. I still enjoy drinking shou pu'er but it's a different tea than aged sheng.
[00:17:09] Jason Cohen: Well, everyone, that's all the time that we have for today. Thank you for joining us in this edition of Tea Technique Editorial Conversations. Please join us again for our next conversation, Firing of Zisha Clay.
