Very Large Handbuilt Pots..possible??

bnsaijim

Actually I believe Al was referring to the price of the kiln itself.

I snagged mine for $400 used. Deals are out there...

Electric kilns are actually more efficient to run than fossil- feuled versions. Especially if you are firing at cone 6 rather than 10... faster to the desired temps, quicker firing times...

While you get less happy accidents, you get less accidents in general.

Pots are just as sturdy and durable. Both "worlds" are equally viable...

If you fire frequently, the money you save on firing fees pays for the kiln in not time at all.

Jim,

TX

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Jay

Hi again, just an update on the pot thing. I have updated the other thread on my progress but wanted to ask another question of the knowledgeable on the future 'large' pot. I have visited the person in charge of the kiln. I had thought the kiln was fired to cone 6, but have learned that it is only fired to cone 5. Will this be a problem with my pots??

Also found out how they determine the cost of the kiln fires. They measure the pot to get a cubic inch measure on a 15x12x3 pot that is 540 cubic inches then times by a factor of .01. So each of the two kiln fireing will be $5.40 or a total of $10.80 for a finished piece. How does this compare to what you know?

On smaller pots the cost can be combined. There is a minimum charge of $5.00 (for two fires) so on smaller pots I submit a few at a time.

__________________
A Bonsai student living with his trees at N 44.37 W 77.49...
Think before you act... then think again... no good comes from rushing

bnsaijim

My "hacker" answer...

Whether you are talking about "O6" and "O5" or 5 and 6 you are not looking at a huge difference in temperatures- like 50 - 60 degrees.

Froma practical standpoint, think of it as bettter than terra cotta which is usually at cone 3-4 but not quite as good as a cheap chinese pot which is probably in the ceramic range of about cone 6. True stoneware, considered the best, is cone 10, i.e., Sara Raynor, Mike Hagedorn, most Tokaname pots...

Ceramics for decorative purposes are often fired at cone 4.

We use some low fire stuff here in Texas- we don't get freezes. It does have a limitted life span due to water absorption and the elements. After three or four years it just starts to crack, chip and degrade...

Your climate has more temperature extremes so I would expect more problems- Cracking from freezing, shorter life spans due to temp swings...

Sincerely,

jim stone
TX

Jay

Jim, thanks for the input. I guess I would be well served to use these pots for Tropicals or for trees wintered in my unheated garage.
If I am correct, the clay is the same but the temp of the kiln is what makes the pots 'harder'. If I was to convince the center to fire once at cone 9 or 10, would it be good enough for the first fire, or do both the initial fire and the glaze fire have to be at cone 10 to get the hardness required??

__________________
A Bonsai student living with his trees at N 44.37 W 77.49...
Think before you act... then think again... no good comes from rushing

bonsaial1

Most pots that are fired to Stoneware, or 75% vitrifacation, are unglazed. If you want to fire to the high temps of 9 and 10, you will need high fire clay and high fire glazes. Cone 10 on reg clay will sometimes explode , and the glazes will fry right off. High fire clay will have more kaolin in it, which by itself is the basis for porcelin. The low fire clay have more impurities in them, since most come right from the ground, hence they explode at the cone 10 temps. If you find someone with a gas kiln, you can fire in a reducing atmosphere, and acheive cone 7/8 with no problem. The pot should last for decades at the level of fire.

Bonsaial

Jay

Thanks Al, this learning stuff is fun... and educational may I add. If my old brain is correct, you are saying that I will not be able to fire the electric kiln (safely) to cone 9 or 10. If I do I need a different clay base and probably different glazes. I will stick with my cone 5 efforts. Is there any difference, other than visual, in glaze and unglaze pots. In particular at this cone 5 level?

__________________
A Bonsai student living with his trees at N 44.37 W 77.49...
Think before you act... then think again... no good comes from rushing

bnsaijim

There would be a color difference...

:^)

If all materials are handled in a manner consistent with their intended use- i.e., if you use all cone 5 materials and fire at that level, all should work out fine.

Clays and glazes behave differently at different temperatures.

There are the differences in strength and durability, as already discussed due to the conversion of ingredients to crystalline states.

If used at other than their prescribed cone, glazes will behave differently- texture, running, opacity... Both clays and glazes will change color.

Going down- the materials would not get hot enough to melt. I think if you used cone 5 materials at cone 9-10 you'd have a wonderful nebari for bonsai sculpture...

(Which I happen to like!)

Jim
TX