Clay pot for dancong - topic expanded to types of mud clays

[the_economist]

I meant something more along the lines of using loose earth/soil mixed with water and coloring rather than mined rocks that have been ground up and processed which is what real yixing pots should be made of.

[entropyembrace]

I meant something more along the lines of using loose earth/soil mixed with water and coloring rather than mined rocks that have been ground up and processed which is what real yixing pots should be made of.

You can't make a tea pot out of loose earth/soil mixed with water and coloring. If you tried to use actual mud to make any pottery, even if it did have a fairly high clay content, it would be impossible to shape.

To use clay from a marginal source like you're describing you need to purify it by separating it from the sand and humus, at which point it would have higher purity than the clay real yixing pots should be made of (which has high levels of iron oxide in addition to the clay minerals).

The "coloring" added to purified clay extracted from a marginal source would be iron oxide. The clay real yixing pots are made of is contaminated with the same iron oxide. The reason these oxides are added to the clay extracted from marginal sources is because at that point in processing they have higher purity than the "rock clay" and need the metal oxide impurities added back in to get the same colour.

So from what you've said it seems "rock clay" is mined from sedimentary clay deposits which have low levels of non-clay minerals other than the high concentration of iron oxide characteristic of yixing clay. This clay can be ground and mixed with water without undergoing purification to produce usable clay.

"Mud" is really pure clay extracted from a marginal source which then has iron oxide added to achieve something similar to the natural yixing clay. There's no reason to think that this clay is dangerous, that practice is common all over the world, and has a long history. You can even do it yourself if you want there's a simple tutorial here: http://practicalprimitive.com/skillofth ... gclay.html there's a series on youtube about it here: https://www.youtube.com/playlist?list=P ... 6C4380EC25 and if you want to make red clay you add iron oxide in the mixing step getting the exact recipe that will work isn't so easy, but you should get the idea.

[blairswhitaker]

haha some of these yixing posts are hilarious to me, yixing people sometimes have the strangest idea of what "clay" is. a basic organic chemistry class and an earth science class could go a loooong way for most of them.

[entropyembrace]

haha some of these yixing posts are hilarious to me, yixing people sometimes have the strangest idea of what "clay" is. a basic organic chemistry class and an earth science class could go a loooong way for most of them.

To be fair I think a lot of the yixing terminology is very confusing, and is maybe suffering from translation problems. It's easy to see how people get the wrong idea about where clay comes from and how it's processed to be usable, especially if they haven't had the chance to see potters mixing and preparing clay before.

[the_economist]

Definitely not a potter, and definitely not claiming any expertise on this. But I think Yixing potters distinguish between clays from sedimentary rocks and clay deposits in the soil (I suppose this is what gets translated as 'rock clay' and 'mud clay'), and I would think there are differences in quality there even if the clay deposits are chemically similar.

As for this particular pot, it is black, and appears not to be very high fired although since I'm not an expert I obviously can't be sure. Either way, I doubt it is due to iron oxide, probably some other dye.

My main point was that this pot doesn't seem to be Yixing nor Chaozhou clay. I'll just end my part in this by saying I wouldn't use that pot for brewing because too many factors are suspect here.

[entropyembrace]

Definitely not a potter, and definitely not claiming any expertise on this. But I think Yixing potters distinguish between clays from sedimentary rocks and clay deposits in the soil (I suppose this is what gets translated as 'rock clay' and 'mud clay'), and I would think there are differences in quality there even if the clay deposits are chemically similar.

As for this particular pot, it is black, and appears not to be very high fired although since I'm not an expert I obviously can't be sure. Either way, I doubt it is due to iron oxide, probably some other dye.

My main point was that this pot doesn't seem to be Yixing nor Chaozhou clay. I'll just end my part in this by saying I wouldn't use that pot for brewing because too many factors are suspect here.

I'm not an expert or potter either, though two of my aunts, are so I've had an over-the-shoulder perspective of it, and dabbled in pottery a bit

I think probably what makes yixing special is that there are deposits of clay sediments there which are usable without mixing in minerals from other sources, and the impurities in those deposits are good for making tea pots

My main point was just because a clay is mined from new sediments (rather than old ones like the yixing "rock" clay) or requires minerals from other sources mixed in doesn't necessarily make the clay bad or dangerous

I'd guess the black colour is iron oxide, that's by far the most common additive to make clay darker, and it's what makes most naturally dark clays have their colour too.

As for the pot itself, that dark v shaped stain seems really weird to me still, and how shiny the outside is compared to inside? Except that the v shaped stain on the inside looks like the outside.

it could just be slip or something harmless like that, but I'm not sure.

[the_economist]

I think you're probably right, it could be some iron oxide compound giving it its color, although it certainly does not look like the type of black clay produced by the older Yixing factories made from blending clay with iron oxide.

I'm not worried about iron oxide or other specific chemicals which may or may not be present, I'm more worried about its apparent low firing and completely unknown provenance of what clay it is. There could be anything in that clay.

[chrl42]

For those who dredge up a science class on Yixing pottery or tea in general are really interesting but I'd appreciate.

It's the tea itself are generally similar in compounds from $2 to $20000, and what fills in between the gap? call it wine or other artistic wares..$2 Yixing pot and $200000 Yixing pot will be similar in compounds if you talk about science class..since they are all clay.

In China, the collector culture is similar to what is seemed in the west as 'art'. Call it a stradivarius or a toy violin..they are both just woods. Be it Xinjiang jade or kyara. Most of jades or kyara on the market are fakes...are there difference? are there?

Beginners would be interested to hear about how tea can help diet or reduce blood pressure, or how Mozart can make you sleep or Da vinci is scientist. But for those who've been doing longer just know there are better ways to lose weight or lower the blood pressure than tea, or hypnotic without listening to music and so on. Reading papers, when would we see the summit of Lao Ban Zhang..or win to blind test?


And from hearing, black color on Yixing are usually done with manganese oxide powder plus cobalt oxide powder. In earlier time, they made with the reduction method (chocking out of oxygen).

[mganz42]

Entropyembrace, it's kind of hard to tell from my photos (sorry about that), but the inside is equally shiny as the outside. I had to use a different camera for the inside because for some reason the first camera wouldn't focus on it properly. Idk if that makes a difference. I'm so inexperienced when it comes to clay

[mganz42]

Also, the_economist, how can you tell that the clay was low fired, and how does that adversely affect the pot? The pot has a bright ringing sound when I knock the lid against the body, I've read that for some clays that indicates a high firing?

[chrl42]

how can you tell that the clay was low fired?

claywares tend to have lower temp to fire than sandwares.

Also, adding oxide powders lower the temp of firing, in high temp it could lead the pots to be cracked in the kilns.

[entropyembrace]

how can you tell that the clay was low fired?

claywares tend to have lower temp to fire than sandwares.

Also, adding oxide powders lower the temp of firing, in high temp it could lead the pots to be cracked in the kilns.

This is true, but keep in mind traditional yixing clay like zhuni has metal oxides that's why zhuni is fired at 1050C and traditional hard paste porcelain that is pure kaolin and alabaster is fired at 1400C, or modern hard-paste that's kaolin, feldspar, and quartz at 1200C

For those who dredge up a science class on Yixing pottery or tea in general are really interesting but I'd appreciate.

It's the tea itself are generally similar in compounds from $2 to $20000, and what fills in between the gap? call it wine or other artistic wares..$2 Yixing pot and $200000 Yixing pot will be similar in compounds if you talk about science class..since they are all clay.

Similar, but not the same, yixing clay is supposed to be hard to work with poor plasticity. If you're mixing imitation yixing probably most people make a mix that's a bit more plastic, can be fired at lower temp ect...to make it easier to use. But then this clay is scientifically different from the traditional yixing clay Probably if you have a sample of high quality natural yixing clay and have the tools to analyse it in detail you could make an imitation mix that is very accurate...but why go through all that trouble to get clay that cracks on the wheel and needs to be carefully hand shaped from slabs when yixing collectors won't spend big money on it if they know what you did?

Though also interesting question...since you can put cheap wine in a nice bottle and talk it up and most people will think it is really an expensive wine when they taste it....so are the expensive things really different, or we just think they are because we're told so?

[chrl42]

how can you tell that the clay was low fired?

claywares tend to have lower temp to fire than sandwares.

Also, adding oxide powders lower the temp of firing, in high temp it could lead the pots to be cracked in the kilns.

This is true, but keep in mind traditional yixing clay like zhuni has metal oxides that's why zhuni is fired at 1050C and traditional hard paste porcelain that is pure kaolin and alabaster is fired at 1400C, or modern hard-paste that's kaolin, feldspar, and quartz at 1200C

I don't think this is that.

In that logic, any Yixing clay contains iron oxides, not just Zhuni. Iron oxides are what basically makes Yixing clay's color.

Zhuni is low-firing is due to its mud-like texture. While normal Yixing clay is basically ore, stone..Zhuni clay is somewhat like mud..high in clay content. (as opposed to sand content). There is a data that old Zhuni contains more alumina content, that data was talking about higher the alumina higher temp the firing. Modern Zhuni like Xiaomeiyao cannot be fired over 1100c, due to too much shrinkage. That data explained less alumina led to higher shrinkage.

Oxide powder-duped clays' easily breakage in the kilns might be due to its mixture composition or others. It's normally iron-rich clays are more resistant to heat (like Jian wares or Bizen).

[Tead Off]

I meant something more along the lines of using loose earth/soil mixed with water and coloring rather than mined rocks that have been ground up and processed which is what real yixing pots should be made of.

You can't make a tea pot out of loose earth/soil mixed with water and coloring. If you tried to use actual mud to make any pottery, even if it did have a fairly high clay content, it would be impossible to shape.

In Yixing parlance, mud is not mud by the western definition. The distinction between softer clay, which is called mud, is usually found in shallower ground, and rock, usually mined deeper, hard like rock, and the need to prepare the rock through a process of softening and curing the clay through proprietary formulas and processes that were held in secret by the various workshops. The outcome of using these two clays is not the same even though you would normally call the clay zhuni or zini or zisha, etc. I'm sure if you did a mineral analysis there would be differences in the clays. Also, the firing, and particle size of the clay, will play a role in how the teapot brews a tea.

In this case, I believe the economist is pointing out that this clay may not even be a Yixing clay, whether mud or rock (using my definition), because of the look of the clay. Hence, his 'beware' statement.

[the_economist]

Also, the_economist, how can you tell that the clay was low fired, and how does that adversely affect the pot? The pot has a bright ringing sound when I knock the lid against the body, I've read that for some clays that indicates a high firing?

I was just guessing based on what the insides looked like from the photos. Even if it is high fired, it doesn't seem like an Yixing or Chaozhou pot.