Tag Archives: Pottery

Made a dent in the wood pile today…

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.

Madara Karatsu

Madara Karatsu. Madara refers to the glaze, usually a high silica white which reacts with the clay to produce a mottled effect, with various shades of white, cream, yellow, brown, and subtle optical blues. Most modern potters use rice straw ash as the main ingredient in their madara glaze, but other types of high silica ash are sometimes used as well.

We don’t know exactly what was in these glazes traditionally, there are probably various combination of glaze ingredients and clay bodies that would yield the madara effect, and I suspect that the potters of old just used what was on hand, which would explain why some of the old kilns are known for specific types of pots. Hobashira-gama, one of the Kishidake Ko-garatsu kilns was probably the best known for its Madara Karatsu ware.

Madara Karatsu Chawan. Name: Hakuo

Hakuo is one of my favorite tea bowls, and a sort of collection of ideal Madara Karatsu traits. The glaze is not too thin, not too thick, the clay is vitrified nicely, but quite sandy so that it reacts well with the glaze. Below is another piece of a tea bowl from Hobashira-gama. This is  a shard that was given to me by a friend.

inside bottom of a tea bowl

You can see the mottling , including the blue spots, probably from ash that settled and melted in the bowl.

detail of clay/glaze interaction

There is a lot of sand in this clay body. You can see here that the glaze is not that thick. Many modern potters apply the rice straw glaze thicker, or too thick (often the case with me), resulting in a white glaze. Too thin and you end up with clear.

foot of tea bowl

When you touch this shard you can feel that it is well vitrified. It does not absorb water. There is a lot of speculation about what the body really is. Recent examination of shards like these under an electron microscope indicate that the clay body is not really clay at all, but rather powdered stone. When people talk about the technology brought to Japan by Korean potters, they always mention the climbing kiln, and glazes. Perhaps more importantly, they also brought over the technology of processing stone into a usable body for making pots. They had this technology for processing porcelain stone, but did not have a source immediately, and made pots for many years before discovering the porcelain stone deposit at Izumiyama, Arita. Suitable types of feldspathic sandstone probably served as alternative ‘clay’ bodies in the meantime.

detail of foot

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.

First Chamber Loaded

Finally! After seemingly endless days of loading, the front is finished. The large pieces in front are most refires with the exception of the large jar to the right. The big white piece in the middle isn’t a pot, it is a large piece of  Shirakawa Toseki (porcelain stone from the Shirakawa area near Arita dam). The square right behind it is a piece of sandstone that I cut in two and hollowed out to make a box.

Kiln Loading

The date for the fall firing is official! 2011/11/11. There must be some sort of astrological significance to this, be it good or bad.

Since I’ve been making a lot or work to go into the kiln for this firing, I’ve been constantly short on ware boards, so decided the best way to free some up would be to get the pots off of them by loading them into the kiln. This has the added benefit of breaking up the loading process so it is not so danged exhausting.

This afternoon saw the completion of the rear setting, all cone 6 ware give or take. E-Karatsu, Kawakujira, and Kohiki. Most everything is smaller and doesn’t have much height, so to fill in the higher spaces many of the pots were balanced on kiln posts. The added benefit to this is that if the temperature gets too high, the pots will collapse, invert around the posts and stick to them completely and utterly. Post-In-A-Cup.

The two jars are refires that had a lot of unmelted ash on the shoulders. In order to melt it, I’ve applied an ash glaze that should melt and flux the sintered ash underneath, hopefully. And, if I’m really lucky, they will slump or split in the firing, sticking to everything around them.

An odd experience

Coming home on Friday, I noticed I was behind a tanker truck which was polished stainless steel. The convex rear of the tank, coupled with the polished surface, made a very nice ‘fish eye lens’ type of mirror.
The odd part of it was: watching myself in the rear of that truck, I could see my car and all of the landscape around me rushing by, but it was as if I was watching me as someone else, or like watching myself in a movie, but in real time. It was kinda cool. I tried snapping some pictures with my phone camera, but they don’t really convey the experience.