Clay porosity

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Youzi
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Thu Jul 22, 2021 1:03 pm

LeoFox wrote:
Thu Jul 22, 2021 10:59 am
Thanks I just did it. I will report the findings a bit later. A very busy day


Okay:

Image


Based on this, the modern zini is more "porous" than reduction mumyoi.

However, reduction mumyoi is much more rounding.

I feel the difference here is possibly more reflective of surface area differences - and surface tension. Both are within 5 ml of volume but zini is flatter and mumyoi is a bit more round.
If you want to evaluate the clay effect, then brewing tea isn’t really helping you. Try comparing them with the (make a lot of tea in a Gaiwan, collect in GDB then separate into the teapots [filled fully], let them sit there for an hour, make sure they are the same temp, then taste from same kind of cups) method.

This will tell you the actual effect of the clay on tea, minus the aroma part.

Anything else is caused not by the clay, but other properties of the teapot. Usually the thermal properties.

In this case porosity means more, than the usual terminology, it means the amount of water the clay can capture. Most teapots (yixings certainly) are impervious to water.
So it’s better to think of them as hills and valleys or mountains and valleys.

Btw, I calculated for you and the estimated Apparent Porosity of your two pots respectively are:

Zini: 0.82% (+/- 0.2%)
Japanese pot: 0.20% (+/- 0.2%)
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Youzi
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Thu Jul 22, 2021 1:41 pm

Okay, so on the first picture you can see my poor illustration of an emptied teapot where the water is trapped in the pores, but there is still some excess water left too, which could be “tapped out” or wiped away.

On the second picture you can see a teapot full with water, the pores saturated.

And on the third picture saturated unsintered clay vs a sintered clay pot saturated with water.

On the first two pictures you can also see smaller particles, which are referred to as the “double pore” structure.
Attachments
Illustration of a teapot after it’s emptied, water trapped in the pores, and pools of water on the “surface”
Illustration of a teapot after it’s emptied, water trapped in the pores, and pools of water on the “surface”
9ACF9867-288C-4C0B-A57D-3C18002701D1.jpeg (158.4 KiB) Viewed 4113 times
Better Illustration of a teapot filled with water
Better Illustration of a teapot filled with water
24DDB132-99A1-46FA-A743-EA5A21CDE37E.jpeg (148.1 KiB) Viewed 4113 times
Left side Un-sintered clay, right side Sintered clay in teapot.
Left side Un-sintered clay, right side Sintered clay in teapot.
7A8916A5-E6BB-48AE-995F-20AE20D65C6A.jpeg (391.51 KiB) Viewed 4119 times
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LeoFox
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Thu Jul 22, 2021 3:47 pm

Thanks for the illustration. Based on the discussions here and in the yixing thread, it seems this topic is quite complex- we are generally talking about open surface irregularities that result in different degrees of water absorption. As steanze aptly noted, the architecture of these irregularities may play a critical role. And if we are to assume a catalytic role of clay, as hypothesized by .m., the density and distribution of catalytic sites will be important. So for example for my carbonized mumyoi, even with lower surface irregularity, all available surface may be quite active given the deep rice husk ash reduction firing.

As for the methods, I find there are pros and cons with both wet surface (youzi method) and heat dried surface (my method)

The pros of youzi method is that it addresses the shallower irregularities on the clay that may capture water. The con is that this method has a lot of room for variability: what if I didnt tap it enough times? What if I didn't wick it right. Additionally, the youzi method may be dependent on water tension effects that would be impacted by the hydrophobicity of the surface in addition to surface irregularities.

The pro of my method is that it is pretty repeatable and it is an attempt to reflect what happens after a typical tea session. The con is that it does not address the water captured in the shallower more open irregularities.

Ultimately, however, both methods fail in terms of predictive value for impact on tea as brewed normally. Whether this means that neither of these methods are fit for purpose or simply that porosity in general should not be considered the most critical attribute for impact on tea - that remains an open question.
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Youzi
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Thu Jul 22, 2021 5:12 pm

I find the problem with your method is that it shows thing's after the fact. We want to know what happens during brewing.

Basically what gets trapped in the clay. You could think of it as a filter. Based on the size of the valleyes different things and amount of those things could be trapped.

In my method only the tapping is variable. If you wipe the surface, you get to the same result repeatedly. Also, based on the variance between the tapped and the wiped measurements, you can get an indication of the roughness of the surface.

Based on my illustrations, you can imagine what I'm talking about.

So my method is a better approximation of what happens during brewing.

Reading all the convos though what I'm thinking that the actual fault is my method is not that the surface is wet, but that the teapot is fully saturated. Which exaggerates the porosity of pots with thin, but deep cavities. However you don't brew tea for 24 hours.

So I think that your timeframe or Victoria's timeframe is better, and actually we shouldn't fully saturate teapots.

So I think what a good middle ground would be between the two methods is:

Fill the teapot with boiling distilled water.
Let the water sit in the pot for 2 hours (about the max length of a session)
And then do my tapped and wiped measurements.

I feel like this might be the most realistic, but controlled and repeatable way to measure the water absorption and thus the porosity of a pot.


Edit:

I'm also thinking if reduction fired, or at least certainly Ash fired teapots should be removed completely from the discussion, because they seem to have weird effects, that skew the data.
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LeoFox
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Thu Jul 22, 2021 5:40 pm

Maybe let's just drink some nice tea :D

I ❤ my reduction pot by the way hahahahaha

There is also another method on wiki:
Imbibition Water saturation method (pore volume = total volume of water − volume of water left after soaking).
Ultimately, the reviewers would probably force us to to use multiple orthogonal methods to shine light on the situation.
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Baisao
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Thu Jul 22, 2021 8:20 pm

Youzi wrote:
Thu Jul 22, 2021 5:12 pm
I'm also thinking if reduction fired, or at least certainly Ash fired teapots should be removed completely from the discussion, because they seem to have weird effects, that skew the data.
Is it the ash glazing or the reduction that you object to?
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LeoFox
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Thu Jul 22, 2021 8:39 pm

Baisao wrote:
Thu Jul 22, 2021 8:20 pm
Youzi wrote:
Thu Jul 22, 2021 5:12 pm
I'm also thinking if reduction fired, or at least certainly Ash fired teapots should be removed completely from the discussion, because they seem to have weird effects, that skew the data.
Is it the ash glazing or the reduction that you object to?
When I first got the reduction mumyoi pot, someone told that it would be great for roasted oolong - so I tried a dong ding.

Sucked the life right out of the tea! And yet it works wonders on a lot of greens! Go figure
.m.
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Thu Jul 22, 2021 9:59 pm

LeoFox wrote:
Thu Jul 22, 2021 8:39 pm
Baisao wrote:
Thu Jul 22, 2021 8:20 pm
Youzi wrote:
Thu Jul 22, 2021 5:12 pm
I'm also thinking if reduction fired, or at least certainly Ash fired teapots should be removed completely from the discussion, because they seem to have weird effects, that skew the data.
Is it the ash glazing or the reduction that you object to?
When I first got the reduction mumyoi pot, someone told that it would be great for roasted oolong - so I tried a dong ding.

Sucked the life right out of the tea! And yet it works wonders on a lot of greens! Go figure
I have a reduction nosaka. It has a strong smoothening effect on teas. I rarely use it, maybe because i rarely drink greens. I suspect reduction firing makes pot more reactive, although i'm not sure why the black iron oxide Fe3O4 in the clay would be more reactive than the red iron oxide Fe2O3.
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LeoFox
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Thu Jul 22, 2021 10:43 pm

.m. wrote:
Thu Jul 22, 2021 9:59 pm
LeoFox wrote:
Thu Jul 22, 2021 8:39 pm
Baisao wrote:
Thu Jul 22, 2021 8:20 pm


Is it the ash glazing or the reduction that you object to?
When I first got the reduction mumyoi pot, someone told that it would be great for roasted oolong - so I tried a dong ding.

Sucked the life right out of the tea! And yet it works wonders on a lot of greens! Go figure
I have a reduction nosaka. It has a strong smoothening effect on teas. I rarely use it, maybe because i rarely drink greens. I suspect reduction firing makes pot more reactive, although i'm not sure why the black iron oxide Fe3O4 in the clay would be more reactive than the red iron oxide Fe2O3.
Not sure about Fe2O3 vs Fe3O4 but I heard there have been studies linking iron content in certain foods with distinct aftertaste. For example ferrous ion (+2) in wine and fishiness:


https://pubmed.ncbi.nlm.nih.gov/19708656/

Moreover, the intensity of fishy aftertaste was increased by the addition of ferrous ion in model wine and suppressed by the chelation of ferrous ion in red wine. Third, potent volatile compounds of fishy aftertaste, such as hexanal, heptanal, 1-octen-3-one, (E,Z)-2,4-heptadienal, nonanal, and decanal, were determined by gas chromatography-olfactometry and gas chromatography-mass spectrometry in dried scallop soaked in red wine. 
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Youzi
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Fri Jul 23, 2021 2:07 am

Baisao wrote:
Thu Jul 22, 2021 8:20 pm
Youzi wrote:
Thu Jul 22, 2021 5:12 pm
I'm also thinking if reduction fired, or at least certainly Ash fired teapots should be removed completely from the discussion, because they seem to have weird effects, that skew the data.
Is it the ash glazing or the reduction that you object to?
Reduction (ash fired) teapots aren't glazed. I'm talking about the way most reduction fired teapots are made in Japan / china.

The reason is, because it seems many people report different effects than what might be expected of the same clay, when it's reduction ( ash) fired .

So it seems that the effect in that case is more related the way they were fired than what clay are they made of, and what are the properties of that clay.
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LeoFox
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Fri Jul 23, 2021 5:16 am

Youzi wrote:
Fri Jul 23, 2021 2:07 am
Baisao wrote:
Thu Jul 22, 2021 8:20 pm
Youzi wrote:
Thu Jul 22, 2021 5:12 pm
I'm also thinking if reduction fired, or at least certainly Ash fired teapots should be removed completely from the discussion, because they seem to have weird effects, that skew the data.
Is it the ash glazing or the reduction that you object to?
Reduction (ash fired) teapots aren't glazed. I'm talking about the way most reduction fired teapots are made in Japan / china.

The reason is, because it seems many people report different effects than what might be expected of the same clay, when it's reduction ( ash) fired .

So it seems that the effect in that case is more related the way they were fired than what clay are they made of, and what are the properties of that clay.
I think this point needs to be mentioned carefully in the porosity report. If you want this to be an outlier, it needs to have adequate data and justification to support that it should an outlier. In this case, I believe it is possible that a reduction pot has very dense concentration of active sites. If that is true, then degree of reduction may matter. Hojo for example claims that his latest batch of reduction nosaka behaves very close to porcelain - while carbonized reduction pot has the stronger rounding effect.

To simply dismiss a class of pots many people love to use because a few instances doesnt fit a theory would probably be unacceptable.

In some ways, by making this point, it also highlights that many other aspects of the pot can have a stronger impact than information on "porosity". Here. It is reduction firing. Then I have also found that wood firing can have very interesting effects. Also, from hearsay, I've heard that kaolonite rich white clays also are very different - and super muting even if with minimal porosity.
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Youzi
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Fri Jul 23, 2021 5:50 am

LeoFox wrote:
Fri Jul 23, 2021 5:16 am
Youzi wrote:
Fri Jul 23, 2021 2:07 am
Baisao wrote:
Thu Jul 22, 2021 8:20 pm


Is it the ash glazing or the reduction that you object to?
Reduction (ash fired) teapots aren't glazed. I'm talking about the way most reduction fired teapots are made in Japan / china.

The reason is, because it seems many people report different effects than what might be expected of the same clay, when it's reduction ( ash) fired .

So it seems that the effect in that case is more related the way they were fired than what clay are they made of, and what are the properties of that clay.
I think this point needs to be mentioned carefully in the porosity report. If you want this to be an outlier, it needs to have adequate data and justification to support that it should an outlier. In this case, I believe it is possible that a reduction pot has very dense concentration of active sites. If that is true, then degree of reduction may matter. Hojo for example claims that his latest batch of reduction nosaka behaves very close to porcelain - while carbonized reduction pot has the stronger rounding effect.

To simply dismiss a class of pots many people love to use because a few instances doesnt fit a theory would probably be unacceptable.

In some ways, by making this point, it also highlights that many other aspects of the pot can have a stronger impact than information on "porosity". Here. It is reduction firing. Then I have also found that wood firing can have very interesting effects. Also, from hearsay, I've heard that kaolonite rich white clays also are very different - and super muting even if with minimal porosity.
I don't think you got what I meant. I just said that they should be treated separately in another category compared to oxidation fired teapots.
- Porostiy
- clay composition
- and ways of firing
- and the effect of these tea should be studied separately in their own realm

if you lump them all together and measure everything at the same time you can't get anywhere or make meaningful correlations.

Studying the whole system together makes sense, but then making claims how parts of that system does separately have an effect on the whole picture without properly studying that part alone just leads to wrong conclusions and false theories, they way all the teapot magic hearsay developed through the centuries. People noticed certain effects teapots causing to their teas, then making random theories as to why, without actually testing if those theories are the actual reason the teapot behaves that way.
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LeoFox
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Fri Jul 23, 2021 6:10 am

I agree that these things should ultimately be disentangled from each other. I also think that from a consumer point of view, the holistic effect needs to be considered.

Here is thing many people don't know about pharmaceutical development. The exact way a drug works - that is - its actual mechanism of action - often is not considered essential compared to the drug's apparent efficacy and safety profile as displayed in human trials. I think part of this reason is that thinking that as long as it works, and we have some understanding of the conditions in which this can keep working, then that is good enough. Whether this is a good approach is controversial but it is practical.

For teapots perhaps most consumers just want to know overall if it is going to have a certain desired effect. Can "porosity" on its own be used as a predictive marker when it's all tangled up in processing and composition etc?

I hear this a lot: "that's a porous pot. It's gonna mute your tea"

I think from this great discussion we've had, we can at least say we shouldn't state that anymore.
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Youzi
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Fri Jul 23, 2021 6:28 am

LeoFox wrote:
Fri Jul 23, 2021 6:10 am
I agree that these things should ultimately be disentangled from each other. I also think that from a consumer point of view, the holistic effect needs to be considered.

Here is thing many people don't know about pharmaceutical development. The exact way a drug works - that is - its actual mechanism of action - often is not considered essential compared to the drug's apparent efficacy and safety profile as displayed in human trials. I think part of this reason is that thinking that as long as it works, and we have some understanding of the conditions in which this can keep working, then that is good enough. Whether this is a good approach is controversial but it is practical.

For teapots perhaps most consumers just want to know overall if it is going to have a certain desired effect. Can "porosity" on its own be used as a predictive marker when it's all tangled up in processing and composition etc?

I hear this a lot: "that's a porous pot. It's gonna mute your tea"

I think from this great discussion we've had, we can at least say we shouldn't state that anymore.
I feel like we are talking about the same thing but we are just misunderstanding each other :D

"The Teapot Chooses the Tea" - is probably the best advice that can currently given to a consumer, so that they try to find someone who has the same teapot and ask them what they think of it.

However if we have false theories, than that same person would just simply go, "Oh, this is Zini, so it must have medium muting, because it's more porous, therefore it'll be good for tea that needs medium muting", then they go ahead and buy that pot and it doesn't even behave like that remotely, or same thing with Zhuni, "Zhuni => not porous => works like porcelain => won't mute" and they don't consider anything else, then they waste their money, because the pot doesn't behave like that.

The above examples are just a simplified versions of all these things we talked about before.

There are/could be many theories out there as to why 100 = A + B + C + D , is "probably because A = 20, B = 30, C = 15, D = 35", but without checking each possible variable and try to "measure their value" in the equation, it's not good for anyone to jump to conclusions and then start giving it out as an advice, to lesser known or newcomers as it is a fact.

Personally I agree with you, that porosity doesn't matter that much.
But I'm more on the side of clay doesn't even really matter that much in the final effect of the teapot on tea. It has a minor role and effect, mostly on bitterness and astringency, as it was suggested / measured in the paper.
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LeoFox
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Fri Jul 23, 2021 6:42 am

That's a great post! Thank you!


I'm very happy this thread is getting more discussion like this.

I was pretty surprised my modern zini -did almost nothing to tea. I was hoping it would get rid of some shu tea stank. It does nothing. But it has great functionality. Awesome pour with no leak and big opening to put chunks in. Great.

I was also surprised how rounding my early 70s hong ni is - and how it shifts things to the aftertaste...and how after multiple sessions, it smells nothing like yancha,,it-but vaguely like roses. Or maybe I am crazy.
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