Tag Archives: guinomi

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. 



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!

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:

Fall 2015

has been busy.

I’ve gotten pretty far behind keeping up with the blog, falling into the bad habit of making small posts to Facebook. One of my areas of increased effort over the next year will be to work more on maintaining the blog, and getting it more integrated with other forms of social media. Trying to keep track of them all is like trying to herd cats.
I had made one promise to show before/after pictures for a couple of pieces, the first of which is the slab/paddle built sake chiller w/ feet and lugs:

IMG_2176
raw unglazed
IMG_2513
Fired piece, Chosen Karatsu style glaze. Matchbook for scale.
IMG_2518
Underside detail. Fired on shells, feet not touching the shelf.
IMG_2516
Glaze detail

 

The other thing I’ve been working on since early this year is getting a usable kohiki/clear glaze combination, because for some reason a lot of customers have been requesting white work. They have also been requesting black, so I’ve been working on getting a reliable semi matte black glaze. Mission not quite accomplished, but I feel I’m most of the way there. Here is the kohiki I’ve come up with and I am happy with it:

Kohiki cups. Cup on the left is unused. Middle has been used a bit, and right has been used a lot. The patina is beautiful in my opinion, and the fineness of the crackle is something I’ve been wanting for a long time in my work.
Various guinomi from 2015, mostly from the fall firing. Guinomi make great gyokuro drinking cups.
Various guinomi from 2015, mostly from the fall firing. Guinomi make great gyokuro drinking cups.
Seabirds on white.
Seabirds on white.
The other thing I have started doing is Japanese kana inspired brushwork
The other thing I have started doing is Japanese kana inspired brushwork, except with English. This cup is decorated with vertical English writing, a Goethe quote I like: “Whatever you can do, or think you can, begin it. Boldness has genius, power, and magic in it.” One of the other said: “Don’t be a dick.” These were more popular than I had anticipated and are currently sold out. Definitely making more!

Here are some of the pieces with the new black glaze. It seems to look best thin, and as with most glazes looks nicer over interesting wild clays rather than processed clays.

Type 1 semi matte black Katakuchi with black lacquer repairs.
Type 1 semi matte black Katakuchi with black lacquer repairs.
Type 1 semi matte black dish.
Type 1 semi matte black dish.
Semi mmatte type 2: two black glazes layered
matte type 2: two black glazes layered, makes a fatter glaze surface.