Tag Archives: ceramics

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.

Fall firing 2016

Open comments and notes

Front came out beautifully, mid stack as well, rear a little cool. Very top of front, mid, and rear were cold. Shelf config caused this, I think, because of the large shelves being close together, creating strata in the heat gradient. The very front shelf with guinomi and chawan was the main culprit, blocking the flame from rising, and directing it under the large shelves placed midway up the front stack. 

In the future I need to stagger the shelf levels during stacking, to allow the flame to travel upward.  Also, block some of the floor level flue channels at the rear of the chamber. Make sure upper flues are fully open. 

Front cones are 9, 10, 11, 12 Orton. 



Shinot Noir

Warning: some Shino enthusiasts may find content in this post offensive and/or snarky. 

When I was in Korea this last  October, the subject of Shino came up. Shino, like Raku, Chawan, and Geisha, tends to have a different set of meanings and expectations, depending on who you are talking to (usually Japanese vs non-Japanese).

Most Shino enthusiasts in Japan get their pantaloons in a twist when they see this smooth orange, white, or carbon trapping glaze that most Americans call Shino. “Sore wa Shino janai” is a  common thing to hear when showing off your American Shino to a Japanese Shino lover.

In Japan, Shino is a combination of clay, glaze, and firing method. The definition is somewhat cramped , and leaves little wiggle room. Same with Raku, Chawan, and Geisha. There is all this history and tradition hanging on at the end of the label, foiling our attempts to  add new dimensions to the term.

Here’s the problem: The Shino purists are vastly outnumbered. Actually, I’m one of them (to a degree) but acknowledge that on the worldwide level, Shino means more  to a whole lot of world potters and enthusiasts. I really wish the word had not been co-opted by English, but it has, so oh well…

Embracing this trend, I have decided to widen the definition of Shino even further. Here are some examples:

Satin black Shino
Flowing matte white Shino
Soft blue Shino
Clear Shino
Bizen Shino
High silica Shino

Unglazed low fire Shino
Petroleum Flex Shino
 
Note:

(I do make a ‘Shino’ glaze, but do not call it Shino for fear of reprisal.)

Slab plates

This is one way I make slab plates. I posted the pictures to FB but am reposting here with descriptions of each step. You can adjust the steps if your clay is more or less forgiving than mine. 

First cut slabs and let them rest overnight to stiffen up some. These slabs are 10mm thick. 


Trim the slab with an undercut bevel, and save the trimmed edges. 


Sprinkle something on your form to prevent the clay from sticking. I use corn starch. 

Place the trimmed slab bevel side down on your form and paddle it THOROUGHLY, from center to edge, then once more evenly all over.  You can use whatever you want as a paddle, here I used a sandbag, but I usually use a wooden paddle. 


Place the trimmed edges you saved back on the paddled slab, followed by a paper towel or other cloth, and your board. Turn over the form to release the slab onto the board. 


Press the center of the slab down gently and let the edge pieces support the edge of the plate. While supporting the edge with one hand, use the other to define a concavity in the bevel with a convex tool. Anything convex and with a curve you like will work. I used a little ball here. Sometimes I use a rib, sometimes a roller, sometimes a clamshell. I like rollers and balls because they compress the edge well. 


Finish and further compress the edge with a damp (not wet) chamois or sponge. Done!

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