Bonsai pot myth?

Joanie

Personally, I suspect that the conductivity was more about the metallic content of the clay than the water content of the clay. Brown stoneware has metallic oxides in it, such as black iron oxide, red iron oxide, and manganese. It may have taken the water in the surface pores of the clay to allow your ohm meter to get a reading... to create a surface that the meter could read. Dry clay is exteremely non-conductive, but wet metallic based clay may not be. However, that's a different question than porosity, although it's a darned interesting experiment.

POROSITY refers to the ability of a material to absorb water. Earthenware pieces, having been fired to a lower temperature, do not fully mature, or vitrify, and as such, allow water to slowly pass through the wall of the pot. The higher the firing temperature, the less water can pass through, so earthenware fired near the 2000 degree temperature will exhibit little porosity, especially if they are glazed. Conversely, pieces fired low, such as red clay planters, fired around 1200 degrees F. will exhibit pronounced porosity. (Remember, all of this paragraph refers to earthenware--Joanie)

At the extremely high temperatures that Stoneware and Porcelain are fired, little, if any porosity is noticed, even if the pot is unglazed.

-- from Glendale College's Intro to Clay

I'll see if I can find a site that talks about clay porosity in more detail....

Joanie

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morea

Dear Joanie

Yes , You are correct !!!!

Sometimes , when the clay comes from a new load.
It always can be a bit different claybody.
So , the new pots fired at stoneware temp. are
tested on porosity .
I test it with the very thin oil you put in a oillamp to burn .
Because this is even thinner as water , and I know for sure
the pots are waterproof .
Kind regards
Morea

RonMartin(deceased)

Two things.
The pot I used was not earthenware but stoneware.
The only difference between the two readings was the water. What made the new circut between the inside of the pot and the outside of it. It wasn't there before the water was put inside the pot. And no there was no leakage. None that I found anyway.

RonMartin(deceased)

Again the same pot. High fired as most good Japanese pots are. No firing , no new clay. Same pot
The only thing that changed is the water in the pot.
Why did the conductivity change.
For the most part you can forget the clay since it is exaxtly the same in both cases.

morea

Dear Ron


Were was the pot with water standing ?
Same place for both times ?
Maybe with the second expiriment the
surroundings of the pot were hotter ?
Or moister ?

A glazed body is closed !!
A unglazed body , yes , sometimes feels cooler,
like moist , for example with rainy weather.
Even high fired super japanes stoneware.
I felt it at Gingko Awards , is the glasshouse !
The big unglazed pots of Mr. Notter's tree's
But the pots were not wet .
I can"t explane it , but it felt good !
I was not supposed to touch ,
so now I have reveiled my little secret !
Kind regards
Morea

RonMartin(deceased)

The pot was in the same place both times. Never moved. My office.
It is air-conditioned so I don't think that the temperture or even the humidity level changed any.
As I said in the beginning it was an unglazed pot. That means that the different types of glazes don't mean squat.
But again something changed

Joanie

See, Ron, I think that the conductivity has little to do with the porosity. I think that when you got the surface pores of the pot wet, you had a surface that your ohm meter could test. Dry, the ohm meter could not pick up a reading. But I think that you were testing the metallic content of the clay, that is what was actually conducting.

Let's think of it another way. Maybe we can puzzle through it. What exactly are we trying to learn? Whether the unglazed stoneware "breathes"? In order to breathe, there would have to be connections between the tiny chambers that make up the pot wall. The air molecule would have to be able to pass from one chamber to another, all the way through from one side to the other. The very best experiment would be to make a hollow ball of clay, with just a little tiny hole in it. Fire it, and then hook it up to a vacuum through a tube in the hole. We could quickly tell whether it could pull air from the outside to the inside that way. But we lack the tools to do that. (Any volunteers??)

Water is bigger than air, a little bit, but each water molecule is still pretty small. So we can assume that if water can get through, then certainly air can get through. As Morea says, she uses an oil to test her clay. She knows that if the oil penetrates her clay, then it isn't fired the way she wants it to be. However, I know that no matter how much oil the surface of Morea's clay will absorb, the oil still won't go all the way through. Why? Because she's using stoneware, and the little chambers in stoneware are not connected to each other all the way through. They are filled up with melting silica when the clay is fired. That process is called "vitrification" and the term for the clay that is fired to this degree is "vitrified". When clay has been vitrified, it simply cannot contain enough spaces in it to allow the water to penetrate all the way through. So there is no way that such clay can "breathe", because there is no pathway for the air.

If you like, I can find a website somewhere that explains the process of vitrification. The clay goes through many stages, as the quartz expands, and the silica melts. Then the quartz contracts as the clay is cooling off. But the end result is that the clay body is not able to be penetrated all the way through by water or air, as long as it has been fired to the proper temperature, or somewhere close to the right temperature.

Joanie

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RonMartin(deceased)

Nah Forget it. This is making my head hurt. Myth or not I'll go with the guys that made up the myth.
They have more than a few hundred year old trees. Most Mythbusters (a show that I am watching at the moment) can only come up with short lived things. No offense meant just a longtime observation.

Joanie

That's okay, Ron. It won't hurt anything to believe in the idea.

Joanie

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