Karatsu potter Okamoto Sakurei just ended a show in Fukuoka this weekend at Gallery Ichibankan. For those of you who haven’t heard of him, Okamoto san is a very talented artist making Karatsu style wares. He is well known throughout the country and one of the top Karatsu ceramic artists today. He will also be doing a demonstration/lecture for the Workshop in Taku 2012: The Simple Teabowl.
During my visit we had a chance to discuss his upcoming presentation, as well as some wood firing diagnostics. Here are some of the pictures from the show. The gallery used a lot of natural light from its windows, which made for a very nice display, however it was not so camera friendly.
Spend a good bit of time sorting and splitting wood for the next couple of firings today. Before the kiln was built, Craig Edwards mentioned on a couple of occasions that having the wood split and sorted makes for a much easier time firing. I understood the need for splitting, but sorting kind of stumped me. I couldn’t understand why sorting for length would help, thinking that one could estimate the volume of wood going in each stoke, more shorter pieces or less longer pieces, right?
This seems to work in theory, but when you start adding in factors like stoking under the grates vs over the grates, or doing the wooden door technique, or side stoking through a smaller hole that tilts down, then the size and length of the faggots gets pretty important pretty fast. Having to sort through a stack for the right size during the firing makes for a stressful time. Having the right size stacked in the right place so that it doesn’t need to be moved a lot really cuts down on the labor.
So, this time I culled out all of the longest wood and split it first, stacking it near the front of the kiln. Shorter fat pieces near the front as well, with thinner pieces toward the middle and rear for side stoking the front and rear chambers. Also a special section of extra long pieces for doing a wooden door type stoke to get over stalls, if they happen. Here are some pictures of the stacks, plus a little potter porn.
Who got the twisted James Taylor reference in the last post? Sorry about that, physical anthropology humor from a previous life.
Anyway, a friend came over yesterday and gave me a crash course in plaster casting. In one of his previous lives, he was a dental prosthetic technician and did casting in various materials for a living. My knowledge of plaster handling and casting jumped about tenfold in 4 hours.
We poured the mold similarly to before, with a couple of differences: he applied whipped cream consistency plaster to the backs of the originals, let it set, then turned them over and planted them in a freshly poured base, so the working side was face up. We cleaned up that surface in running water before it set completely, then applied separating agent and poured a different colored super hard type of plaster over the working surface of the originals. Then we leveled everything off with regular plaster. Mold finished.
Once completely set, I took the mold and soaked it in hot water for an hour to let it absorb as much water as possible, which helps the separating agent to work, and also keeps the plaster from absorbing liquid from the resin mix, which keeps the resin more fluid. Once the separating agent was applied to all surfaces, I put the mold together and tied it with old bicycle tire rubber, stood it up and poured in the resin. Then after letting the full mold sit for about 15 minutes, put it in a 50C bath for 30 minutes to cure the resin. This time I literally used the bath, and set the hot water temp for 55C. Much easier than a pot on the stove.
Once the curing was done, I let the mold cool, popped it open (which was easy with the proper separating agent) and out came two very nice gyubera. After trimming off the excess, and sanding them with a flap wheel and some 180 grit wet paper, they were finished. Victory! There were some small air bubbles but nothing like before, and the mold is in great condition for next time.
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.
So, in indulging my fixation, I had another try at Ido teabowls yesterday. Still not getting it somehow, but am happy with the bowls as bowls. One of the problems was the clay. Too nice, too smooth. It was recycled from some sandy stuff, but in recycling, much of the tooth was lost. I re-added sand, but not enough.
If I hurry, these might make it into the kiln for the Nov. 11 firing. Feldspar glaze, raw glazed and once fired. Who knows, perhaps some good could come of it after all…
Some other things from the last firing included teabowls, sign post caps, katakuchi, and a lot of hammer fodder. Been having problems with my Chosen karatsu lately, the ame-yu is not playing nicely like it should, and this firing for the first time ever, I ended up with pinholing in my regular madara-yu. This is usually a very dependable glaze for me so I am kind of mystified and perplexed. The only difference from the usual was the clay, so I’ll start diagnosing the problem from there.