Puuurple clay, puuurple clay~

[NaoTK]

Hey all,

I am obsessed with replicating authentic Japanese and Chinese clay bodies, such as Yixing purple clay and Tokoname clay. This thread is capturing my progress and I welcome your input.

The qualities of a good Asian clay body as I see it are:

1. High smoothness and burnish capability. So this means little or no grog and sand
2. Depth of color and subtle variation. This means no artificial oxides or colorants, only natural clay sources for color
3. High maturation temp and low porosity (cone 8-10)
4. Good color response in flame
5. Low shrinkage and warp, glaze fit
6. Good throwing qualities

It was rather challenging to hit all those points. I began with a number of American and Canadian raw clay materials and just iterated for 2 years.

2018-2019: I developed a number of different recipes


2020 July candidate: 20" oval. This clay has the best working properties with moderate color response. I didn't burnish this one but I will make another and it should take a high shine and remove the roughness (August/sept)


2019 candidate with high boron content. This one has the worst working properties but best color. It shrinks terribly and cannot be thrown.


Unburnished 2020 candidate


Still fine tuning the recipes. I will do another run for August with burnishing and also some more slab forms. stay posted!

 

[Pitoon]

@sorce this thread is for you......

 

[penumbra]

Outstanding. I can appreciate all the work going into your testing. I have had clays custom blended in the past but I can't see I will do it again. Blending my own? Too much work for me.
I have used clay from 5 different companies and if they don't have what I am looking for, I'll settle for what they have. I really do appreciate what you are doing though. Almost no one but a potter can understand the work involved in choosing a clay that fits your requirements for bonsai pots. As an example, one company I buy from must have over 60 clays yet only 3 are suitable for me.
Again, I am in awe over what you are doing.

 

[sorce]

@sorce this thread is for you......

This level of persuit is beyond me! Going down the "rabbit hole", but also mating with each rabbit in it, and doing the genome study of the lot afterward!

Respect.

I would like to "pick it apart" if this is ok with @NaoTK .

Sorce

 

[sorce]

As an example, one company I buy from must have over 60 clays yet only 3 are suitable for me.

Knowing you know this makes me know I will surely own one of your pots someday, hopefully soon. Even if I have to steal it, rather, pry it from @Carol 83 cold dead hands! Lol!

They certainly do not cater to the Bonsai Pot Potter.

Sorce

 

[NaoTK]

Outstanding. I can appreciate all the work going into your testing.

Thank you, I'm glad there are folks out there who understand. Like you I probably tried most commercial clay bodies out there before saying "screw it."

 

[sorce]

My friend, I must be honest, the first time I saw that blue and red pot I was like "bullshit", so I must ask for your forgiveness there. Skeptical shouldn't turn into rudeness. It was only after I saw this clay body work, that I realized I wasn't informed enough to call BS, even if in my own head.

It doesn't matter in the slightest at all what potters I have Respect for, but you have entered this small list.

People, especially Bonsai people who sincerely care about their trees, should be aware of the feat this is.
I feel it's nothing short of seeing the mountain, having the asthma, and continuing to the peak successfully. Many, including myself, will stop at the sight of the mountain, giving up well before considering breathing.

I can't commend the effort enough.

To keep thoughts concise...

Morce

 

[Carol 83]

pry it from @Carol 83 cold dead hands

I dare you to try.

 

[sorce]

1. High smoothness and burnish capability. So this means little or no grog and sand
2. Depth of color and subtle variation. This means no artificial oxides or colorants, only natural clay sources for color
3. High maturation temp and low porosity (cone 8-10)
4. Good color response in flame
5. Low shrinkage and warp, glaze fit
6. Good throwing qualities

1. I understand the burnishing process, to pack down the sand and grog particles, so you "should?" Be able to get a shine with sand and grog.
This is confusing to me, because I don't "see" a 20inch pot being even possible without sand or grog. This is beyond my climb! Thoughts?

2. Define artificial? As the "chemical" argument has been going, I don't see any oxides or colorants (besides encapsulated Mason stains?) As "artificial". Though I understand the integrity of

only natural clay sources for color

I'm not "against" additives of these colors. Should I be?
Also, I feel like these additions, give "depth of color and subtle variation", quite specifically.

Do note the use of "feel like" as "feel like", not as "I know". (That's for others, I believe you know this)

That's all for the numbers, but for some further "semantic" mentions....

It shrinks terribly and cannot be thrown.

Does "terribly" mean "greatly" here?

Or terribly like, no matter what kind of attempts to dry slow and evenly, it is truely terrible and always fails?

Do you measure shrinkages?

I guess there is a ....

5. I don't believe warpage has to do with clay body, as much as it has to do with how the clay body is treated. Thoughts?
(I'm poking holes in my theory about that already)

One last thing I would like to get your input on if you will...
I carbon cored my iron rich bodies my last firing, so I did some research and got to thinking....
There really is no way to avoid carbon coring in a woodfired kiln, unless everything is bisqued, which I don't believe happens.
And from my limited observations, it seems this color variation and reduced bodies are part of what makes some pots so visually appealing.

Is it possible that with all the hoops that a bonsai Potter goes through to make a quality product, are we allowed this "out" of having carbon cored bodies?

I have tested things to 0% absorption that are black inside.

So is it sensible to think the weakness of the carbon coring is only apparent, or susceptible to root strength, and/or, the freezing of things inside the pot? Since water will not enter the body itself?

Appreciate the Conversation!
Greatly!

Sorce

 

[NaoTK]

I feel it's nothing short of seeing the mountain, having the asthma, and continuing to the peak successfully. Many, including myself, will stop at the sight of the mountain, giving up well before considering breathing.

Thank you Sorce. This means a lot.
When you're climbing a mountain its hard to tell how close you are to the summit. I may only be half way up that mountain but your words will help me the rest of the way

 

[penumbra]

I'm not "against" additives of these colors. Should I be?
Also, I feel like these additions, give "depth of color and subtle variation", quite specifically.

I am quite found of using natural oxides and carbonates for color. Honestly, even though I sometimes go to great lengths with my glazes, I prefer naked clay.

 

[sorce]

Thank you Sorce. This means a lot.
When you're climbing a mountain its hard to tell how close you are to the summit. I may only be half way up that mountain but your words will help me the rest of the way

I can not take complete credit for this.

I would love to see us all achieve our peaks.

Sorce

 

[NaoTK]

@sorce

I have been dying to have this conversation for years!

1. I understand the burnishing process, to pack down the sand and grog particles, so you "should?" Be able to get a shine with sand and grog.
This is confusing to me, because I don't "see" a 20inch pot being even possible without sand or grog. This is beyond my climb! Thoughts?
The problem is, and you know this, when the pot is fired the fine clay shrinks and the rough particles start to protrude, so you sort of have to exclude the fillers. When you exclude fillers, the clay will now dry and fire unevenly leading to stress and cracks. You can combat this by tuning the silica and ball clay content to enable large forms. Most stress originates in uneven drying imo. Remember most asian pots are molded which helps enable larger forms.

The asian clays also contain grogs and sands, but they are finer. So I have experimented with finer mesh silica sand and grogs. You get the bet of both worlds.

2. Define artificial? As the "chemical" argument has been going, I don't see any oxides or colorants (besides encapsulated Mason stains?) As "artificial". Though I understand the integrity of
I'm not "against" additives of these colors. Should I be?
Also, I feel like these additions, give "depth of color and subtle variation", quite specifically.
Do note the use of "feel like" as "feel like", not as "I know". (That's for others, I believe you know this)
That's all for the numbers, but for some further "semantic" mentions....
In natural iron-bearing clays, the iron is "bound" to silicon over eons of time, along with impurities that give the purple, yellow, brown colors (B, Mn, Ti etc.) It will melt differently from free iron oxide added in later. So it may look the same chemically on paper, but it sure doesn't behave the same way.

Does "terribly" mean "greatly" here?
Or terribly like, no matter what kind of attempts to dry slow and evenly, it is truely terrible and always fails?
I meant it shrinks a shit load, which is 4 metric crap tons. During both drying and firing. As you know it then needs to be dried super slowly. If you keep plasticizers (bentonite, veegum) out of the mix, you wont be able to throw it, but it will dry more evenly.

Do you measure shrinkages?
Yes, I keep detailed notes on shrinkage at different cones and atmospheres. I then tune the silica content so it matures at the right cone and has lower shrinkage.


5. I don't believe warpage has to do with clay body, as much as it has to do with how the clay body is treated. Thoughts?
(I'm poking holes in my theory about that already)
Yeah, its all about memory and stress in the clay. You may have thrown a perfect circle now but then the stress comes into play when fired. But I meant the qualities of a clay can also contribute to the warping, if the maturation temp is inappropriate or its overloaded in oxides which is a flux. You know its just getting the absorption to bottom out at just the right temp.

One last thing I would like to get your input on if you will...
I carbon cored my iron rich bodies my last firing, so I did some research and got to thinking....
There really is no way to avoid carbon coring in a woodfired kiln, unless everything is bisqued, which I don't believe happens.
And from my limited observations, it seems this color variation and reduced bodies are part of what makes some pots so visually appealing.
Is it possible that with all the hoops that a bonsai Potter goes through to make a quality product, are we allowed this "out" of having carbon cored bodies?
I have tested things to 0% absorption that are black inside.
So is it sensible to think the weakness of the carbon coring is only apparent, or susceptible to root strength, and/or, the freezing of things inside the pot? Since water will not enter the body itself?
I think carbon coring is unavoidable if you fire in reduction, even if you bisque. They are definitely more brittle now, but I have carbon cored pots with absolutely no frost issues (the box I posted for example). I haven't broken a famous famous Japanese pot, but I have broken a yamaaki pot. They fire in near-oxidation. They may fire in complete oxidation with a strike. That is always an option for us. I know most tokoname potters bisque fire first.

I'm happy to discuss more anytime

 

[sorce]

They're even pretty premixed!

I dried the rest of my red river clay to make another larger batch of this clay.


Do you use machinery to mix?

I have been hand mixing and pouring them into denim legs.

Those are pretty low shrink numbers.... interesting.
I wonder what the qualities are that they seek in commercial clays that make their shrink 10-12%.

Sorce

 

[Trenthany]

1. I understand the burnishing process, to pack down the sand and grog particles, so you "should?" Be able to get a shine with sand and grog.
This is confusing to me, because I don't "see" a 20inch pot being even possible without sand or grog. This is beyond my climb! Thoughts?

2. Define artificial? As the "chemical" argument has been going, I don't see any oxides or colorants (besides encapsulated Mason stains?) As "artificial". Though I understand the integrity of

I'm not "against" additives of these colors. Should I be?
Also, I feel like these additions, give "depth of color and subtle variation", quite specifically.

Do note the use of "feel like" as "feel like", not as "I know". (That's for others, I believe you know this)

That's all for the numbers, but for some further "semantic" mentions....



Does "terribly" mean "greatly" here?

Or terribly like, no matter what kind of attempts to dry slow and evenly, it is truely terrible and always fails?

Do you measure shrinkages?

I guess there is a ....

5. I don't believe warpage has to do with clay body, as much as it has to do with how the clay body is treated. Thoughts?
(I'm poking holes in my theory about that already)

One last thing I would like to get your input on if you will...
I carbon cored my iron rich bodies my last firing, so I did some research and got to thinking....
There really is no way to avoid carbon coring in a woodfired kiln, unless everything is bisqued, which I don't believe happens.
And from my limited observations, it seems this color variation and reduced bodies are part of what makes some pots so visually appealing.

Is it possible that with all the hoops that a bonsai Potter goes through to make a quality product, are we allowed this "out" of having carbon cored bodies?

I have tested things to 0% absorption that are black inside.

So is it sensible to think the weakness of the carbon coring is only apparent, or susceptible to root strength, and/or, the freezing of things inside the pot? Since water will not enter the body itself?

Appreciate the Conversation!
Greatly!

Sorce

I’m lost at the levels y’all take pottery to but I just wanted to note that you should never ask a man, potter or not to measure their shrinkage...

 

[quietobserver]

I’m lost at the levels y’all take pottery to but I just wanted to note that you should never ask a man, potter or not to measure their shrinkage...

But the water was soo cold

 

[NaoTK]

Do you use machinery to mix?

I have been hand mixing and pouring them into denim legs.

Those are pretty low shrink numbers.... interesting.
I wonder what the qualities are that they seek in commercial clays that make their shrink 10-12%.

Sorce

Good stuff, I didn't know about that denim technique.

I am pretty low tech and small scale (50lbs at a time) so I put all my dry goods in a thick trash bag and evenly mix, then I add water and kneed the bag. No dust, no mess. I add a bit of barium carbonate to prevent salt leaching. This tends to outgas so I recommend making a slurry and adding it to the bag. The bags work out because I can label them and if they dry out I just add water.

I guess commercial clays use a lot of kaolin which have high shrinkage but good drying properties. In retrospect I should reformulate my mixes to be higher in kaolin to deal with the uneven drying issues we discussed earlier. The journey continues

 

[Anthony]

The Yi Xing clay formulas are published,

It is high fire earthenware 1180 deg.C collapses.

The body has a fine grog, so it dries well.

Fine clay slip is used as a coat over the body and a cow horn
does the burnishing. [ think terra sigillata ]

The colour is often iron oxide, so you can buy purple, red etc.
------------------------------------------------------------------
Our clays fit the Chinese range so it is easy to duplicate.
Good Day
Anthony

 

[Anthony]

!!!!!!!!!!!!!!!! BEAUTIFUL WORK !!!!!!!!!!!!!!!!!!!!!!!!!!!

 

[Bonsai Nut]

I know nothing about pottery... but I do know a few things about bad water, and how different water (from the tap) can be from location to location.

Do you test your water? If your water is hard or soft does it matter? Or are the level of minerals and salts too low to make an appreciable difference when working with ceramics?