Category Archives: wood kiln

I have this recurring nightmare…

before every firing of the wood kiln. Actually it is four separate recurring nightmares. In the first, I am loading pots onto normal wood shelves in a fairly standard living room, for some reason not worrying that the lot of it will burn up with the entire house. BUT, for some reason, I always remove all of the lamps and light fixtures, because they and they alone can’t handle the  high temps.

In the second, we are firing the kiln as usual, and we are into the third day, just hours before finishing and I realize that I FORGOT TO LOAD THE KILN… This one is by far the worst of the dreams. The feeling of sudden panic is positively sublime. Very happy to wake up (and realize it was just a dream) after this one…

The next is not quite as bad as the previous, but still pretty unsettling.  It starts out well enough: I have just unloaded a very successful firing and am so happy with it that I decide to fire again. Because it is a dream, I miraculously have enough glazed ware to load the kiln up again in about 2 days (Normally takes me 10). I get everything loaded, and start the fire, but about a day into the firing I realize I ONLY HAVE ONE DAY WORTH OF FIREWOOD! This one also wakes me up with that icky panicky feeling.

The third is not a nightmare per se, but a recurring dream about a kiln that doesn’t exist. It is a large single chamber, with white interior, and there are shelves on the walls and in the center of the large chamber on a sort of island. The floor, walls, and island are all white and rough with kiln wash. There is no chimney, and the kiln is connected to the fire box via an elevated brick tunnel, which goes out the rear of the chamber about 2 meters, turns 90 degrees right, stretches about 8 meters, then takes another 90 degree right turn, where extends forward and turns into the firebox. From the firebox to the kiln forms a large U shape. Even more strange, the firebox is open to the sky and steps up to the flue channel, which somehow ‘sucks’ in the heat of the fire. The firebox is probably 4 meters long/deep, and the wood used is huge: entire tree trunks shoved in and stacked in a criss cross pattern, burning.  Any one have a kiln that looks like this?

Coming up to this fall firing in Oct., I feel as though everything is under control, and no particularly strong feelings of anxiety, yet the dreams continue, including 2 nights in a row now, a dream of some of my teeth falling out. Seems quite normal in the dream at least…

Postfire thoughts

Well, time to sit down with the last firing and figure out what went wrong, and what went right.

Firing and packing: Great. With this firing I figured out, FINALLY, the proper exit flue volume to use. And with it, the proper packing procedure. The kiln climbed steadily, without effort, for 45 hours and the flame in the front chamber reached front to back really nicely. It turned out to be a fairly even gradient from front to back, from cone 13 in front, to a good melted 8 in back. No sidestoking necessary.
I am going to go back to using a pyrometer for the next firing, because this firing got very reduced. I think the stoke intervals were too close, and a pyrometer may help me get a better idea of temp climb timing, and when each cycle goes into oxidation.
At one point, when we switched to stoking the 2nd chamber, the temp just started dropping. You could tell from the sound and color of the kiln. I jabbed a pyro into a peep hole and it told me right away that I was stoking to frequently. After the flame had receded into the chimney and peepholes, and the roar had died away was when the temp really started climbing in the chamber. I had been stoking when the flames receded and the kiln quieted down, but once I started waiting rather for the temp to start dropping after the rise, the kiln got back on track. This rise took longer than I imagined, sometimes up to 10 minutes. Had been stoking waaayyyyyy too much.
This firing was a watershed moment for me, regarding packing, air, and stoking. I think next time will finally be the load that makes us all smile.

Glazes: Glazed ware in the second chamber turned out really nice. Reduction was still too heavy, but we got nice surfaces. Still, I won’t aim for that in the future. Madara glazes were too yellow for my taste. The first chamber glazes were so reduced that whatever their intended color, everything turned out a semi matte green, from the excessive iron pulled from the body saturating the glaze and crystallizing. I think the stoking interval will fix this problem.

Clay body: Oops. Here is where the shit hit the fan. Too much iron, especially considering the temp and amount of reduction that happened. The clay I used for the large pieces has too much iron for that type of firing environment, which is why they almost all collapsed. Having worked with a gas kiln for so long, it is hard to get out of the mindset of adding iron rich clay to other whiter bodies in order to get a desired color. The white clays in this area have enough iron for good color in a wood kiln. I keep forgetting that, but perhaps the shock of this latest meltdown, and the subsequent pain of shelf grinding will serve to jog my memory whenever I’m mixing clay for the wood kiln.

We got this off the shelf in one piece! The attached cup sits level when you set the piece on a table, so great for sashimi and  sauce or condiments.
We got this off the shelf in one piece! The attached cup sits level when you set the piece on a table, so great for sashimi and sauce or condiments.
The Fall of Icarus
The Fall of Icarus
Arm detail
Arm detail

Spring Firing Wood

is split, stacked, and ready to go. Now all I need are some pots to fire….

the last of it. splitting done.
Douglas fir stacks next to kiln
four palettes of slender cedar and pine, two palettes of douglas fir.
the stuff that wouldn’t fit on the kiln side of the studio

Of late…

I have been busy. Just seems like there is no time for blog posts. Here are some pics of stuff going into the kiln for the upcoming firing in the new year.

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Porcelain cups. Coil built.
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Small food dishes
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Dish feet
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Casting insulating blocks for kiln doors.

This next firing will be longer than previous firings, about 3days, which means a lot more wood to prepare. Gasp. Argh.

Bummer…

This just made me sad when I saw it this morning. We had a LOT of rain over ten last 36 hours, and I think the footers sank a bit, tilting the stack forward, then dumping it. This will take some time to clean up.

** Just one quick amendment to this post: on re-reading the post and comments, I realized that I may have mislead people to believe that the stack (chimney) went over. Not so, thankfully. Just the stack of wood. No damage to the kiln other than a few scratches to the insulating top coat, and about 5 unlucky shelves that had been sitting right where the wood struck.


-Posted from iMike

Location:Taku, Saga, Japan

The First Pots: Chawan and Guinomi

Here are some of the first pots to get cleaned up after the firing last week. I’ll post more over the next few days as I get things cleaned up.

Overall the firing went well, much better than the first two certainly. I’m finally starting to get a grip on how the kiln climbs, and learning not to worry about it too much. We fired both chambers this time and it took roughly 30 hours. Cone 10 flat in front, cone 9 touching in the rear, and cone 13 almost touching in the second chamber. The second chamber is a pleasure to fire, very relaxing after stoking the front. I think I can still get more aggressive with the front, taking the temp up even more, probably somewhere around cone 12 would be good for the rice straw ash glazes.

The intention was to drop cone 6 in the rear and call it quits, but it ended up getting hotter than expected, and the ware in front ended up a little too shiny. However, the middle and rear of the setting came out just about perfectly. Temp from top to bottom was quite even. We stopped stoking the second chamber when cone 11 dropped and clammed everything up after letting some of the excess heat out. Still, when I peeked in the next morning, that second chamber was still glowing, and cone 13 was mostly down. Guess that 1250kg of insulating castable does its job well.

Most of the failures this time around were caused by bad glazing, not the firing. Rice straw ash glazes were universally too thick, and an ash glaze I whipped up hoping to be a nice runny green ended up being a crusty reddish brown. Oops.