Clay porosity

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LeoFox
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Wed Jun 30, 2021 12:50 pm

Recently tested the porosity of early 70s hong ni and kobiwako.

Essentially no change for 70s Hong ni. I tested this 3 times.

Kobiwako shifted only about 0.04 g!! This is after months of disuse followed by hours long session with boiling water. This clay does not seem to be that porous despite having a marked impact on the tea.
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Baisao
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Sat Jul 03, 2021 3:34 am

I’ve long suspected that the porosity of clay is only part of the reason for the noted effects. I’ve used “porous” loosely to refer both to the porous nature of a clay and its texture. It seems that that the approximation works well enough for us but it has led to some confusion over what is actually causing the effects.

I can think of a handful of reasons that the so-called muting effect is occurring. One or more of the following may be at play:

* porosity (duh)
* texture
* ion exchange
* chemical processes

There are bound to be more but these come to mind as possibilities. Note that the first two are essentially describing an increase in surface area.
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Baisao
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Wed Jul 14, 2021 12:40 pm

Great job with the study. A myth has been busted but questions regarding the role of surface chemistry remain.
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LeoFox
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Wed Jul 14, 2021 1:29 pm

Baisao wrote:
Wed Jul 14, 2021 12:40 pm
Great job with the study. A myth has been busted but questions regarding the role of surface chemistry remain.
Thanks. Unfortunately, I don't have more pots with me and I don't plan on getting more, so the sampling is limited:

viewtopic.php?p=37062#p37062
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Youzi
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Wed Jul 21, 2021 3:21 am

@LeoFox
How did you do your porosity measurements? And what equipment did you use to measure it?

Also, how did you evaluate the effect of the clay and separate it from the effect of the teapot?
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LeoFox
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Wed Jul 21, 2021 5:48 am

Youzi wrote:
Wed Jul 21, 2021 3:21 am
LeoFox
How did you do your porosity measurements? And what equipment did you use to measure it?

Also, how did you evaluate the effect of the clay and separate it from the effect of the teapot?
I explain how I measured porosity in my first two posts.


I'm not sure what you mean by "effect". if you mean impact on tea, I am simply reporting on my subjective experience when using the teapot in comparison to porcelain gaiwan. On occasion, I did do something like brew tea in gaiwan and incubate tea in the different teapots and compare side by side. I found however this rarely reflected how the pot actually brewed tea so i stopped doing it. The effects I am reporting are generally very obvious.
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Youzi
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Wed Jul 21, 2021 5:55 am

LeoFox wrote:
Wed Jul 21, 2021 5:48 am
Youzi wrote:
Wed Jul 21, 2021 3:21 am
LeoFox
How did you do your porosity measurements? And what equipment did you use to measure it?

Also, how did you evaluate the effect of the clay and separate it from the effect of the teapot?
I explain how I measured porosity in my first two posts.

I'm not sure what you mean by "effect". if you mean impact on tea, I am simply reporting on my subjective experience when using the teapot in comparison to porcelain gaiwan. On occasion, I did do something like brew tea in gaiwan and incubate tea in the different teapots and compare side by side. I found however this rarely reflected how the pot actually brewed tea so i stopped doing it. The effects I am reporting are generally very obvious.
then how do you know that what you are sensing is the result / effect caused by the clay and not the teapot? Did you do the tests side by side with the gaiwan? And did you also make sure that the concentration of the two brew were the same, and same temperature and the same cup was used for sampling? (if you don't have a brix meter, then you can do it by making sure the two teas are the same color, you need two, same glass cups for that)

by measuring porosity I meant that did you use a 0.01 scale? And to my understanding, to saturate the teapot you did a couple sessions with it continuously, then measure the weight right after the session, but you rinsed with boiling water, to dry the pot?
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LeoFox
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Wed Jul 21, 2021 6:10 am

Youzi wrote:
Wed Jul 21, 2021 5:55 am
LeoFox wrote:
Wed Jul 21, 2021 5:48 am
Youzi wrote:
Wed Jul 21, 2021 3:21 am
LeoFox
How did you do your porosity measurements? And what equipment did you use to measure it?

Also, how did you evaluate the effect of the clay and separate it from the effect of the teapot?
I explain how I measured porosity in my first two posts.

I'm not sure what you mean by "effect". if you mean impact on tea, I am simply reporting on my subjective experience when using the teapot in comparison to porcelain gaiwan. On occasion, I did do something like brew tea in gaiwan and incubate tea in the different teapots and compare side by side. I found however this rarely reflected how the pot actually brewed tea so i stopped doing it. The effects I am reporting are generally very obvious.
then how do you know that what you are sensing is the result / effect caused by the clay and not the teapot? Did you do the tests side by side with the gaiwan? And did you also make sure that the concentration of the two brew were the same, and same temperature and the same cup was used for sampling? (if you don't have a brix meter, then you can do it by making sure the two teas are the same color, you need two, same glass cups for that)

by measuring porosity I meant that did you use a 0.01 scale? And to my understanding, to saturate the teapot you did a couple sessions with it continuously, then measure the weight right after the session, but you rinsed with boiling water, to dry the pot?
For the effect on tea, I've done several side by side and have had a lot of experience just using them across many sessions. In terms of color, I used visual. In remote of temperature, I did not measure them, but probably no more than 5C difference apart when side by side. I've also compared them completely cooled down versus hot. Some of the clay differences are more apparent when hot. But the ones I describe here are very obvious to me. In terms of trying to make it as rigorous as possible - I decided not to because I don't brew like this and it would take too much time. It wouldn't be useful for me and i suspect no matter how stringent I am about amounts and temp and Brix etc, other people may not be satisfied. So the results i report are not based on some formally validated approach with established specificity, accuracy, sensitivity, ruggedness etc. But they are what is useful at least for how I am mostly brewing the tea, which I suspect is close to how many people brew tea on here.

Yes I used a 0.01 g sensitive scale and I rinsed to dry pot. Most had very little difference and dried out 5-10 minutes - three that had significant difference were obvious and took a while to dry out. The scale I check with calibrate weights about once a month. Have not needed to do any calibration so far. It has a 100g max, which prevents me from measuring my heavier bizen.

Perhaps the ideal would be if several pots can be made with same shape and similar volume and same clay but with different firing procedures to achieve a range of porosities - and then tested side by side multiple times with one tea and by a group of experienced tea drinkers that have shown a degree of alignment. But who can and would be willing to do this other than a teapot/tea company? And if so, who can trust their report since they have a profit motive?
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Youzi
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Wed Jul 21, 2021 12:23 pm

@LeoFox
The reason you get inconsistent results is because the way you measure the water absorption introduces too many points for failures in measurements.

For example you let the surface of the pots dry completely. This will make the measurements flawed, showing higher water absorption for thinner but deeper pore structure pots (smooth surface), while the ones with shallow but wide pores (rough surface) will show basically no porosity.

If you want to measure the accessible porosity (water absorption actually).
Then you have to let the teapot surface stay wet. The way I do my measurements is that I use a non absorbing garbage tea towel. Like some tangpin ones. Which doesn't absorb water, and just wipe the wet surface of the pot, just to remove water droplets.

Also, using hot boiling water and pouring it out will evaporate most of the surface level water also skewing the result.

I tested many different ways to measure water absorption accurately and reliably. And the best way I found is:

Measure dry weight ( a couple day is enough for pots to get completely dry)

Fill the pot with distilled water
Let it sit there for 24 hours
Pour out
Tap dry it ( to remove most excess water)
Measure the weight
Then wipe with a non absorbent or wet cloth, to get more accurate results
Measure again

So you'll have
Dry weight
Saturated (tapped) weight
Saturated (wiped) weight

By the formula you mentioned you can get the water absorption amount and %.
If you give me those numbers I can give you the estimated accessible porosity % too.
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LeoFox
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Wed Jul 21, 2021 12:29 pm

When you say my results are inconsistent, you mean inconsistent with the hypothesis that porosity scales with rounding?

So you are saying with your wet pot method, you find good correlation with muting?

I will try it with 2 pots- one I know is muting and one that is not

I will use modern zini (neutral) and my reduction mumyoi (rounding). Incubation has just started. They have about the same volumes and are close in mass.

Excited to see if this method works. My criticism is that it doesnt seem to mimic real world brewing conditions, but if it somehow matches my rounding experience, then great. Seems easy enough to do.
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Youzi
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Wed Jul 21, 2021 1:10 pm

LeoFox wrote:
Wed Jul 21, 2021 12:29 pm
When you say my results are inconsistent, you mean inconsistent with the hypothesis that porosity scales with rounding?

So you are saying with your wet pot method, you find good correlation with muting?

I will try it with 2 pots- one I know is muting and one that is not

I will use modern zini (neutral) and my reduction mumyoi (rounding). Incubation has just started. They have about the same volumes and are close in mass.

Excited to see if this method works. My criticism is that it doesnt seem to mimic real world brewing conditions, but if it somehow matches my rounding experience, then great. Seems easy enough to do.
I mean your water absorption measurements are inconsistent, because they negatively effect shallow more porous pots, compared to thin but deep porous pots.

It depends, when you did the pour from the gdb into the pots and let it sit method what differences you found. Tbh, I’ve been researching and studying this topic for the past two years mostly. Together with other teapot properties and their effects on tea.

However I don’t think you’ll find the results to correlate with your senses during brewing, because the effect is too minimal and other properties like the heat curve of the teapot effect the brew much more significantly. That’s why I’d strongly suggest you to separate the complete teapot effect and the effect of the clay. Because so far from the research I’ve done (modern yixing pots) the clay effects weren’t too big, however they were inline with my porosity measurements. More porous pots “muting” more, less porous pots “muting” less.

However during brewing these effects weren’t consistent with they teapot’s effect. Unless the pot was really porous then the effect could be noticed.
So far based on the tests I did, peak heat and the cool down curve of the pots had a much bigger effect.

You could improve on my method if instead of water you’d use pre brewed tea. However that’ll introduces more variables that can skew your results.
The point of these are not to get real life number, but to get repeatable and steady results with the least amount of possible errors while trying to emulate real life methods, so that you can see patterns from your data.
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LeoFox
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Wed Jul 21, 2021 1:14 pm

Youzi wrote:
Wed Jul 21, 2021 1:10 pm
LeoFox wrote:
Wed Jul 21, 2021 12:29 pm
When you say my results are inconsistent, you mean inconsistent with the hypothesis that porosity scales with rounding?

So you are saying with your wet pot method, you find good correlation with muting?

I will try it with 2 pots- one I know is muting and one that is not

I will use modern zini (neutral) and my reduction mumyoi (rounding). Incubation has just started. They have about the same volumes and are close in mass.

Excited to see if this method works. My criticism is that it doesnt seem to mimic real world brewing conditions, but if it somehow matches my rounding experience, then great. Seems easy enough to do.
I mean your water absorption measurements are inconsistent, because they negatively effect shallow more porous pots, compared to thin but deep porous pots.

It depends, when you did the pour from the gdb into the pots and let it sit method what differences you found. Tbh, I’ve been researching and studying this topic for the past two years mostly. Together with other teapot properties and their effects on tea.

However I don’t think you’ll find the results to correlate with your senses during brewing, because the effect is too minimal and other properties like the heat curve of the teapot effect the brew much more significantly. That’s why I’d strongly suggest you to separate the complete teapot effect and the effect of the clay. Because so far from the research I’ve done (modern yixing pots) the clay effects weren’t too big, however they were inline with my porosity measurements. More porous pots “muting” more, less porous pots “muting” less.

However during brewing these effects weren’t consistent with they teapot’s effect. Unless the pot was really porous then the effect could be noticed.
So far based on the tests I did, peak heat and the cool down curve of the pots had a much bigger effect.

You could improve on my method if instead of water you’d use pre brewed tea. However that’ll introduces more variables that can skew your results.
The point of these are not to get real life number, but to get repeatable and steady results with the least amount of possible errors while trying to emulate real life methods, so that you can see patterns from your data.
I'll soon see how good your method is.
:twisted:
J/king

It seems you have studied this for quite some time. Are you in the teapot business?
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Youzi
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Wed Jul 21, 2021 1:48 pm

LeoFox wrote:
Wed Jul 21, 2021 1:14 pm
Youzi wrote:
Wed Jul 21, 2021 1:10 pm
LeoFox wrote:
Wed Jul 21, 2021 12:29 pm
When you say my results are inconsistent, you mean inconsistent with the hypothesis that porosity scales with rounding?

So you are saying with your wet pot method, you find good correlation with muting?

I will try it with 2 pots- one I know is muting and one that is not

I will use modern zini (neutral) and my reduction mumyoi (rounding). Incubation has just started. They have about the same volumes and are close in mass.

Excited to see if this method works. My criticism is that it doesnt seem to mimic real world brewing conditions, but if it somehow matches my rounding experience, then great. Seems easy enough to do.
I mean your water absorption measurements are inconsistent, because they negatively effect shallow more porous pots, compared to thin but deep porous pots.

It depends, when you did the pour from the gdb into the pots and let it sit method what differences you found. Tbh, I’ve been researching and studying this topic for the past two years mostly. Together with other teapot properties and their effects on tea.

However I don’t think you’ll find the results to correlate with your senses during brewing, because the effect is too minimal and other properties like the heat curve of the teapot effect the brew much more significantly. That’s why I’d strongly suggest you to separate the complete teapot effect and the effect of the clay. Because so far from the research I’ve done (modern yixing pots) the clay effects weren’t too big, however they were inline with my porosity measurements. More porous pots “muting” more, less porous pots “muting” less.

However during brewing these effects weren’t consistent with they teapot’s effect. Unless the pot was really porous then the effect could be noticed.
So far based on the tests I did, peak heat and the cool down curve of the pots had a much bigger effect.

You could improve on my method if instead of water you’d use pre brewed tea. However that’ll introduces more variables that can skew your results.
The point of these are not to get real life number, but to get repeatable and steady results with the least amount of possible errors while trying to emulate real life methods, so that you can see patterns from your data.
I'll soon see how good your method is.
:twisted:
J/king

It seems you have studied this for quite some time. Are you in the teapot business?
No, I’m in the wasting money and too much time on this stuff business. :D :D :D
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Youzi
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Thu Jul 22, 2021 10:11 am

@LeoFox
Btw, tap drying means that you hit the pot upside down against your palm, with a tea cloth in it. Not tapping the cloth on the inside of the pot.

And when you to to the second wiping step it's better to measure more than once to see how the weight changes.

Usually I do it till the weight stabilizes and the wall still feels wet to the touch.
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LeoFox
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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:
SmartSelect_20210722-134204_Sheets.jpg
SmartSelect_20210722-134204_Sheets.jpg (149.84 KiB) Viewed 100 times

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.
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