Tag Archives: karatsu

8th Wood Firing Photo Record

This post is a photo record with comments, in order to organize and retain my thoughts and observations about the 8th firing of the wood kiln. I always think I’ll remember until the next firing, but never do. So, if you get into this, beware there are a LOT of pictures, some of which may seem redundant. There are examples of most of the pots from the firing, minus teabowls and some others which are not photographed yet.

The 8th firing was a charm overall, with many good pots, some bad, and some that will get refired. Kiln was fired in oxidation primarily. We stoked once every 30 minutes for 2 1/2 days, then once every 20 minutes the last half day.

– Front was nicely melted, nice even gradient to the rear of first chamber, E-Karatsu was about ideal. Cone 12 at hottest front down to cone 6 at coolest rear.

– Front chamber behaves like anagama. No significant temp gradient from front to back of each setting. Next firing, will pack kiln by eliminating the space between settings, leaving horizontal space for flame travel. One long setting from front to back of first chamber.

– Ame yu better at low temps. Load rear to mid chamber.

– Ao yu needs more heat, mid to front chamber.

– Large platters go midway to back of front chamber. Too much ash up front.

– Firebox wares are very nice in a three day firing. Great place for Shino, under cover to avoid ash in pots.

– Rear chamber fires fast when preheated for 3 days. Jumped from 1044C to 1344C in four stokes, a little over an hour. Care must be taken to spend more time soaking at high temp, because rear chamber high temp wares not quite mature (surface changes only), clay not melted well. Spend 3 or 4 hours firing off rear chamber, slowly, to get inside the pots.

– Rear chamber fires very evenly front to back, and top to bottom. Pick a temp to fire at and load accordingly. Don’t expect a significant gradient.

 

Keeping track of clay

As I may have mentioned before, buying the pugger/mixer was probably the best decision I made last year. It has made my life easier in so many ways. However, it has made things more difficult in one way: it is hard to keep track of all the claybodies that go into the kiln. Especially after they are made into something and drying on the shelves, it is very difficult to tell them apart.

When I fired with the gas kiln, stuff didn’t pile up all that much, because I fired frequently. Now with the wood kiln getting fired 3 times per year, things tend to stack up, and labeling is essential to avoid hideous mishaps. I try to keep types of clay consistent from wareboard to wareboard and label each board, but packing pots in the kiln to bisque them means losing the labels and taking extensive notes, because bisqued clay looks even more similar than green.

The other day, I was wishing I had a way to label the pots better, then it came to me: a labeling app on my smart phone with which to label photos in my gallery. I downloaded a free app (there are lots of different ones), and viola!, pictures taken of my bisque load shelf levels are now accurately labeled and instantly backed up to my home network, so I know I won’t lose them.

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Now if significant time passes between firings, or just unloading a bisque, I can refer to my pictures to figure out what everything is.

Salvage

Finally getting back to work after a very long hiatus, looking forward to posting to the blog much more. I spent some time this last couple of days repairing a large jar that had fallen over during a firing. It had stuck to the floor in a couple of places and when we pulled it up it took a couple of big chunks out of the pot.
I have been saving some knots from a pine board and the nuts were filled with pitch and very hard. when polished they were actually quite translucent and when oiled they shine really nicely. I never decided what they would be good for but when I saw this hole in the jar I thought one of these might be the perfect way to fix it.
I don’t have a picture of the original hole but this is the hole after I ground it out and created a gallery for the wood knot.

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Here it is lit from the inside.

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And finally with the lacquer in gold treatment.  This is a reddish gold color because it’s not actually gold, but rather a mixture of brass and mica.

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New Paddled Water Jars and Flower Vases

Here are the first of a bunch of water jars and flower vases that are going into the kiln this early fall. I really needed some practice coiling, paddling, and collaring in necks on the kickwheel and 船徳利 funadokkuri (boat flasks) are the perfect shape for it. Traditionally these were used as flasks for oil, etc. on boats. They needed to be hard to tip over, hence the wide flat bottom. Now they are mostly used for flower arrangements.

All of the water jars will have wooden lids made for them. I’ve done one or two in the past with surprising positive response from viewers/customers. The lids are fun to make, since they are a non traditional item, you can play around a bit with them. I’ll post some lids later on, if the pots make it through the firing.

3 boat flasks and one taller crane necked flask
3 boat flasks and one taller crane necked flask
water jars. any marks in the clay need to be pretty over the top, because the glaze covers them over for the most part.
water jars. any marks in the clay need to be pretty over the top, because the glaze covers them over for the most part.
lug and lip detail
lug and lip detail
more jars, a couple with 'nail heads' added, instead of lugs. You sometimes see these on tea cups and food dishes in Karatsu ware.
more jars, a couple with ‘nail heads’ added, instead of lugs. You sometimes see these on tea cups and food dishes in Karatsu ware.

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all together now... The tallest flask is about 28cm tall,dry.
all together now… The tallest flask is about 28cm tall,dry.
Karatsu meets pueblo water jar, with kneeling, bowing tea person receiving tea. This started as a lug and sort of went bananas from there. This could be one of those things where I later slap myself.
Karatsu meets pueblo water jar, with kneeling, bowing tea person receiving tea. This started as a lug and sort of went bananas from there. This could be one of those things where I later slap myself.
Tall necked vase with two pairs of tea people bowing.
Tall necked vase with two pairs of tea people bowing.
Karatsu meets pueblo water jar. sorry for the order here...
Karatsu meets pueblo water jar. sorry for the order here…
Lug detail. I really must have wanted to drink tea that day.
Lug detail. I really must have wanted to drink tea that day.
boat flask with porcelain additions. Here's the big question: Will they pop off upon drying?
boat flask with porcelain additions. Here’s the big question: Will they pop off upon drying?
tall necked flower vase with lugs, (finally some normal ones)
tall necked flower vase with lugs, (finally some normal ones)

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 Results

Ok, lots of things to say about this last firing, but with the studio show starting tomorrow I just don’t have time for a long post. Here are pictures instead, commentary and contemplation about these results will follow in a few days…