Bonsai pot myth?

Joanie

If it works, it works. Now I'm trying to find a site or two that discusses Japanese clay bodies used for bonsai pots. Does anyone have a reference?

Inquiring minds want to know....

Joanie

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HB Smith

When the roots grow in a glazed interior, they tend to just circle the pot over and over. When the interior is rough, they tend to get more ramified, with the result being a more highly branched root structure. That's all there is to this.

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Sincerely,
Howard

www.BonsaiSmiths.net

Repotter

I have seen roots form circles in unglazed pots as well. So I don't think that has any bearing on it.

Any tree that has an aggressive root system if left long enough without repotting will circle the pot. Ficus is one example.

Hec

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The original Four Seasons Bonsai Club of Michigan.
Guest master Pedro Morales visit was a huge success.
Tellys Greenhouse, 3301 John R road, Troy Mi. 48083

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Vance Wood

What ever side of this argument you come down on there is one thing I can say with certinty, if you use glaze pots they better be the highest fired pots available or they crack over the winter if you leave a tree in them. There are few affordable glazed pots. The good ones are expensive and the cheap ones are expensive----in that they will not survive more than a year or two outdoors 365, and you will be replacing them.

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The only finished bonsai is a dead one; me 1992 MABA Des Moines Iowa

Repotter

Yes Vance, thats why I use glazed for indoor most always and unglazed for my outdoor trees.

__________________
http://www.tellys.com

http://www.Fourseasonsbonsai.com
The original Four Seasons Bonsai Club of Michigan.
Guest master Pedro Morales visit was a huge success.
Tellys Greenhouse, 3301 John R road, Troy Mi. 48083

Four Seasons Bonsai Club meetings monthly.
Troy, Michigan

"Anything is possible when you don't know what you are doing"................someone famous I think.

Joanie

I can't speak to the glazed/unglazed as it applies to pots cracking in winter temperatures, but the idea that glazed cracks and unglazed doesn't is counter to most potters wisdom. However, I did find a few references to the surface water being able to escape from unsealed concrete which seemed to imply that the surface of the concrete would last longer in winter temps if the pores on the outside were left unsealed. They were talking about surface problems more than the cracking of the entire wall, however.

The cracking of pots in the winter would have more to do with what's inside of the pots, right? It would be the expansion, from freezing, of the soil and root mass. So surface water would not be a factor, instead it would be the strength of the clay wall.

Maybe the pots that you have had problems with, Vance, were made of cheaper clay than the unglazed ones? Were they of the same quality, or from the same potter? Most potters use the same clay for their glazed and their unglazed pots, so a side by side would be the best way to find out. I can't think of any reason why a glazed pot should crack, and an unglazed pot of the same clay, doesn't.

Joanie

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Vance Wood

I think that's what I said, they were not the best quality, they were in fact Chinese. However they were all made by the same maker, and the unglazed pots purchased at the same time were identicle excepty they were not glazed. The unglazed pots have held up fine. I was however promised that the glaze pots would hold up and they did not. Despite what some potters may tell you, I can tell you from experience that the glazed pots, if they are not really fine quality with break.

I have to add this as well, I would not purchase a pot glazed on the inside I think it hinders the ability of the plant to breath, can I prove it?----No, can you or anyone else prove that it doesn't? NO! But what is happen here is not the action of temperature by itself it is the action of water.

For those of you who may have forgotten some of your High School Chemistry water is a very interesting compound. It cannot be compressed, no matter what you put water into and what kind of force is applied to it, it cannot be compressed into something smaller. Any force applied to it will be transfered to what ever is compressing it or what ever is containing it.

Either way, when something gives it will be the container or the compressor but not the water. Another cute feature of water is what happens when it freezes. It expands and causes what ever it is in to expand with it unless, there is some room for that expansion, or some flexibility. That's why things heave out of the ground over the winter, and that is why I believe that external glazed pots will break. The internal terracotta will expand, the glaze will not, the glaze cracks and when the pot tries to contract the glaze prevents it from doing so and the pot breaks.


In that one feature lies the problem and probably suggests the theory that unglazed pots do absorb a little moisture. When that moisture expands it causes the unequal surface of the glaze to expand but being brittle (the glaze)it cracks instead. Can I prove this? ----No. But I do know I will not buy glazed pots for outside trees unless it is a tree that absolutely needs a glaze then I will pay the big bucks for it.

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The only finished bonsai is a dead one; me 1992 MABA Des Moines Iowa

RonMartin(deceased)

My ohm meter experiment way back in #7 of this thread seems to prove you right Vance.

Joanie

Vance, to really understand what you are saying, I need to understand what you all mean by "cracking". Do you mean big, long cracks all the way through the pot? Or do you mean fine, cobweb like cracks in the glaze?

I guess this is what I am struggling with... if you mean fine, cobweb like cracks on the glaze, I agree with you. The expansion and contraction of glaze is quite different than that of fired clay. The glaze will not expand nor contract in the same way, and it CAN POSSIBLY cause these cobweb cracks. Potters call this "crackle" and they use it for decorative purposes. How they make a crackle in their glaze is by using the same forces you are talking about... mismatching the shrinking of the glaze with the shrinking of the clay wall. Of course, they are using the heating of the kiln for their temperature changes, not the freezing of a Michigan winter!

If it's long, full cracks that go all the way through the pot, then it is the clay body that is at fault, not the glaze. A cheaper, and less strong, clay body would crack whether it had glaze on it or not. In fact, if the clay body truly is holding onto water, then glaze should help the problem because it would seal at least one surface of the pot. I think that when you buy export glazed pots, you are buying pots made with cheaper clay rather than good clay, because the expense goes into the glaze and the second firing required for glazing. Also, the glaze MAY fire at a lower temperature than the clay should mature at. So it is poor manufacturing practice, NOT the glaze itself.

If you bought a good pot from Dale, let's say, who uses excellent clay and most likely uses the same clay for his glazed and unglazed pots, then the glazed pot you bought from Dale would not crack in the winter. Or, if it did, it would crack whether or not it had glaze on it.

Like many discussions here, that is a subtle difference... but if people start saying that "glazed pots crack in winter and unglazed don't", they will hurt the sale of glazed pots from potters who make a good product, and whose product will not crack. It's the underlying problems that cause the cracks, not the glaze itself.

Hope I am communicating better today, because I don't want to fight with anyone, but I sure do want to be clear when we talk about products that people depend on for their livelihood!

Joanie

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