Tag Archives: workshop in taku

Processing Clay

I was lucky enough to find some easily accessible clay the other day on a morning bike ride. I’ve been spending some time processing it and thought I’d share. Here’s the hill and the pictures of the bagged clay:

 

After bringing it home, I transferred it to large jars and added water, then mixed violently with a drill mixer to break it all up.  After skimming off the junk that floats up, I mix it up a few times a day for about 3 days. Once it is mostly made into a slurry I start sieving it into another container. Whatever doesn’t pass the sieve goes back in the jar to get mixed again, and it eventually (mostly) all breaks down.

Since I have no space for a large clay drying platform, I’ve decided to try these pantlegs tied off, filled, and left to hang. Seems to be working so far, and I’m hoping to get a nice uniform sausage of clay with no dry edges. I tried a few methods to close the bottom. First, I tried sandwiching the pantleg between two pieces of wood and using screws to tighten them together. This worked, but left sharp screw ends, and when I dropped one full leg, the wood snapped and it opened up, spilling the clay.  Plywood might prevent this. Being too lazy to get out the saw and cut more wood, I decided to split what I had into thinner pieces and wire them together to bind the folded over leg end. I tied them with wire and it seems to be working just dandy. Later, when I have time, I’ll try  finding some sort of non rusting clamp device that can be applied and removed easily and quickly.

Once the legs were filled, tying them off was tricky because a leg full of clay slurry is FRICKIN HEAVY!!! First I tried rolling it down over the rope and tying, which works fine but is kind of tricky and if you don’t do it tightly, it unwinds and makes a mess. I found the best way was to twist the end and bend it over a stick, then bind it with rope. This way, you can use the stick as a handle to carry the leg which is very nice, and the stick can be used to hand the bag. The rope used to bind the end can also serve as a hanger. I hung up 12 of these yesterday, and am now waiting for them to firm up. I’m curious to see how long it will take.

Firing for anyone

In Japan, people often visit pottery studios for a short pottery experience, either painting something or making something small to be glazed and fired later by the studio owner or a craftsman. This has always seemed so limited to me, and the inevitable comment, “Oh, you are so lucky, I wish I could do this every day!” always prompts my response: “Yes, me too!”. Most people just don’t have any idea what goes into a finished pot. Turning it on the wheel is maybe 10% of the overall process, much less if you gather materials yourself and/or wood fire  your work. And customers rarely see the failures, or all the polishing that goes into a piece and assume the potter just opens  the kiln door to a batch of warm, super looking, ready to sell pots.

Finding a way for people to experience more of pottery making is a challenge, because of the time it takes drying, bisqueing, firing, and waiting to cool down. Raku firing abbreviates this a lot, but still requires a lot of specialized equipment in most cases. Shichirin fired pottery, for me, is a good way for anyone to have a firing experience, including the excitement of the fire, the engagement with the work, the post fire polishing and critiquing, and even the failures and serendipitous successes.

Lately I’ve been working on a firing method that is accessible to everyone, with items available at most home centers. I got this idea years ago when a Japanese potter named Yoshida (don’t remember his first name) made a splash by introducing “Shichirin Togei”, which used a  small Japanese BBQ, called a shichirin, to fire small objects. This developed into a book called Minigama, which I never read, but outlines the construction of small handbuilt kilns from fireclay and fired with wood, charcoal, and forced air. I think the book is out of print now.

I liked the idea of shichirin togei, but thought the open shichirin was maybe not so efficient at getting up to temp, so I added another one on top, like a clamshell, with both shichirin wadded together with a coil of clay. The bottom damper is the air port, and the top damper is the chimney opening and stoke hole.

You start by packing some charcoal into the bottom of the chamber, around a stilt on which the pot will sit. Then place the pot on the stilt and continue covering with charcoal. Then place a coil of soft clay around the mouth of the shichirin, and overturn the second shichirin over it.

Now that that is done, time for the fun to start! Use a hand torch to light charcoal, then use a hair dryer to get things burning hot.

Now just wait for things to heat up, it will take a few minutes, after which flames will start to emerge from the top damper hole.

This flame should continue to grow and get jumpy, making noise as unburnt gases from inside the chamber exit and combust when they meet more oxygen.  Keep slowly adding pieces of charcoal from the top stoke hole (damper), keep that flame extended. As it gets nice and hot, you’ll be able to tell how the kiln breathes every time you put in a piece of charcoal, and you’ll get a sense of when to stoke.

The first firing might take about 45 minutes, because of the time to heat everything up. From the second firing, 30 minutes seems to be enough to fire the clay. If you have time, you can go longer, and ash from the charcoal will leave more green ‘glaze’ on the surface of the pot.

2016-03-20 Glaze tests 釉薬の実験

Fired with cones 6,7,8 on top and bottom shelves. Pyrometer at middle shelf, didn’t display over 1215C.
Hotter on bottom than top. By cone, looks like cone 9+ on the bottom, cone 9 at the middle, and cone 8+ at the top.

Reduction strong at top shelf, weaker at middle and bottom.

棚三段、上、中、下。 オートンコーン6,7,8 使用、上:下置。温度計は中に。焼成中の温度計は1215Cを超えずが、上は8番コーンは曲がって、ヘタレ。下は8番フラット。 実際の温度は下:9+、ちゅう:9、上:8+ とみていいでしょう。
上は還元効いているようだが、中:下は中性気味。

Unloading:

Bottom shelf, front. Mid shelf, rear left. Top shelf, rear right.
Bottom shelf, front. Mid shelf, rear left. Top shelf, rear right.
Top shelf
Top shelf
Mid shelf
Mid shelf
Bottom shelf
Bottom shelf
Bottom cones
Bottom cones
Top cones
Top cones

 

Clay : Ash Blends  (Lft, to Rt.:  Bott.,Mid.,Top)

Taku shiro 90 : Dobai 10
Taku shiro 90 : Dobai 10
Taku shiro 80 : Dobai 20
Taku shiro 80 : Dobai 20
Taku shiro 70 : Dobai 30
Taku shiro 70 : Dobai 30
Taku shiro 60 : Dobai 40
Taku shiro 60 : Dobai 40

 

Stone : Ash Blends    (Lft, to Rt.:  Bott.,Mid.,Top)

Sandstone 90 : Dobai 10
Sandstone 90 : Dobai 10
Sandstone 80 : Dobai 20
Sandstone 80 : Dobai 20
Sandstone 70 : Dobai 30
Sandstone 70 : Dobai 30
Sandstone 60 : Dobai 40
Sandstone 60 : Dobai 40

 

Clay : Ash total, plus 280g Shirakawa

Clay:Ash total +280g toseki
Clay:Ash total +280g toseki

 

Stone : Ash total, plus 280g Shirakawa

Stone:Ash total + 280g toseki
Stone:Ash total + 280g toseki

 

Everything dumped together: Stone:Clay:Ash:Shirakawa

Clay:Stone:Ash:Toseki total
Clay:Stone:Ash:Toseki total

 

Stone:Ash 70:30 from top shelf (cone 8+) in the sunlight:

Stone:Ash 70:30 @ cone 8 1/2
Stone:Ash 70:30 @ cone 8 1/2

IMG_3681

Hunting white clay (not elephants)

There is an old story around here about Nakazato Muan (12th Generation Nakazato Tarouemon, Living National Treasure) finding a really great white clay seam in the Azambaru area of Taku.  Here it is in Japanese for those of you who can read it:

中里窯は昭和二十一年に石炭使用の角窯を薪用に改造して二十五年まで焼いた。
土は主に多久高麗古窯址近くの多久市北多久の荕(あざん)原(ばる)白土を胎土とした。
この土を見つけた時のエピソードが残っている。
掘り出した土を叺(かます)に詰めて荷車で重利が梶をとり、多久駅まで運ぶ途中下り坂に差し掛かった。
後押ししていた無庵は、下り坂でも押しまくった。はずみのついた車に重利はあわてて梶棒から飛びのいた。
車はそのまま道脇の田圃に突っ込み、荷車は壊れてしまった。
重利が驚いて怒鳴ると無庵は,
「この土で何を作ろうかと考えていたので下り坂に気付かなかった」と重利に謝った。
「親父が俺に謝ったのはあの時がはじめてだった」と重利はいう。

For those of you whose Japanese is a bit rusty, it goes like this:

In the year Showa 21 (1946), the Nakazato kiln was converted from a coal burning kiln to a wood burning kiln, and it was fired until Showa 25 (1950). During this time, Muan mostly used a white clay from the Azanbaru area of Taku.  There is a story, told by his son Shigetoshi, from the day they discovered this clay seam (Nakazato Shigetoshi passed away in 2015, at the age of 85, so he was probably around 16 years old at the time of this story).
So they have all this clay loaded onto a cart, which Shigetoshi is pulling and his father Muan is pushing, to Taku train station.
On the way, they reach a downward slope, and without noticing, Muan keeps pushing  down the slope, and they almost run into a car speeding down the road. Shigetoshi ends up diving to avoid the car, the car ends up in a rice field, and their cart ends up broken.  When Shigetoshi gets angry and starts yelling, Muan says “I was so busy thinking about what I was going to make with this clay, I didn’t notice the slope.”,  apologizing to Shigetoshi.
“That was the first time my father ever apologized to me.”, Shigetoshi commented.

So why, you say, are you telling me all of this? Well, the fabled white clay seam has been looked for now by other potters for decades with no luck, but due to a fortuitous event a few months ago (and several years of looking), I believe I have found it again. Here are some pictures from our excursion out to dig some sample material for testing.

This looks promising, with the moss scraped away.
This looks promising, with the moss scraped away.

 

Making some progress, this small hole yielded over 100kg of clay.
Making some progress, this small hole yielded over 100kg of clay.

 

Two partners today, one is my mentor, in the foreground, the other a friend and fellow artist.
Two partners today, one is my mentor, in the foreground, the other a friend and fellow artist.

 

Under better lighting. Isn't it gorgeous?
Under better lighting. Isn’t it gorgeous?

 

Oh, and lastly, here’s a picture of one of Nakazato Muan’s coil and paddle built jars. This one is made from white clay from the clay seam pictured above. My firing tests have almost the same color as the unglazed bottom section of this jar (although it is hard to see from this dark picture).

IMG_3605

Gas Firing 2016.02.20 Comments and Notes

This firing of the kiln went too long, resulting in Orton cone 11 flat.  Ideally, it would be cone 11 touching, then sagging a bit.

Upon unloading the kiln this morning, one thing was immediately apparent: the right side was far more reduced than the left. Yellower glazes and more slumping. Even on the left side there was some slumping, because of the excessive temp., and because of the clay which contained some low temp high iron clay to help seal the ware against leakage.

Left side, sagging only slightly, white surface.
Left side, sagging only slightly, white surface.
Right side sagging badly, white glaze turned yellow.
Right side sagging badly, white glaze turned yellow.

Chosen Karatsu came out pretty good, but the white was on too heavy, running down the pots too much.  It still came out looking ok because of the clay.

Most of the teabowls warped or sagged, so I only get to keep 2 or 3 of the 15. This is why teabowls are expensive, kids…IMG_3399 IMG_3398

All in all, not a bad firing, but need to adjust clay bodies, and pay closer attention to cones. Also, figure out the over reduction on the right side. It might be that one burner that sounds a bit off.

Kakewake CG bowls
Kakewake CG bowls
guinomi, need more sand in the clay
guinomi, need more sand in the clay
crystals, only grew on the right side, where reduction was strongest.
crystals, only grew on the right side, where reduction was strongest.
cylindrical tea bowls
cylindrical tea bowls
yunomi
yunomi
shells on feet
shells on feet

IMG_3437

saggared and much improved.
saggared and much improved.
porcelain, saggared
porcelain, saggared

IMG_3464 IMG_3463 IMG_3462 IMG_3460 IMG_3459

 

2015 Christmas Firing

was a real nail biter.  At 4am, 10 hours into the firing, I realized that I had not gauged my propane reserves properly, when I looked at the tanks and realized that they were only about 1/5 full and covered with a thick layer of ice. I immediately put the water hose on them to melt the ice and keep them from freezing again, then I chewed my nails until 8:30 am when I could finally call the gas company for fresh tanks. They arrived just after 9am, and good thing to because I only had about 2 inches of fuel left in the tanks at that point.

The firing ran a total of about 18 hours, which is fairly normal for this type of firing, and most things came out ok, with a few exceptions: