All posts by KaratsuPots

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.

Scoring Goodies

I made a trip out to the mountains in Minamihata yesterday with my mentor to collect materials for pots and glazes, and we stopped by an old kiln site as well.

We were able to collect a good amount of feldspathic sandstone, weathered feldspar, and the ever popular grey stuff (don’t know what its real name is).

First, here is what we collected that will become pots and glazes this year:

The lot of it
Grey stuff. This is softer than rock and can be stamp milled or pot milled easily into a fine slurry. It has a lot of iron, and I use it as a glaze ingredient, as a slip, or as a pigment for decoration.
Sandstone. This has more iron than I’d normally like, but beggars can’t be choosers. It takes the place of both feldspar additions to clay bodies as well as grog. I like it because it helps the body vitrify, but gives it texture as well.
More sandstone.
Glaze stone from near Okawachiyama. I’m not sure but I believe this is the glaze stone used in Nabeshima celadon. I look forward to testing this.
Closeup. You can see the feldspathic translucent pieces in the matrix, surrounded by the white powdery matrix. I think the white powdery part is high in silica, but again, need to test.
Found this in the same place as the Nabeshima glaze stone. This looks to be more pure feldspar. Very curious to see how it fires!

On the way to one of the collecting sites, we passed two old Karatsu kilns, Fujinokawachi and Kayanotani.  I was surprised because they are separated by no more than 70 meters or so. These were big kilns. Kayanotani was a 22 chamber climbing kiln 52 meters long! Between them, there were probably hundreds of potters working. We couldn’t really access Fujinokawachi, but we were able to walk around on the hill where Kayanotani once stood.

Access to Kayanotani. You can see the faint grassy steps up the hill, just to the left and down a bit from the tree.
Sign board standing at the entrance to the kiln site. The shard pile extends up and down the hill to the left of the sign.
The outside surfaces of some coil and paddle flasks. Fujinokawachi and Kayanotani are both known for their fine coil and paddle work.
Interiors of the same. Note the different clays used and the different patterns created from the paddling tools.
Hillside littered with shards and chunks of kiln wall and kiln furniture.
The feet of some ash glazed bowls. The clay is quite light in color, and really vitrified.
Detail of some flask lips. On the one, you can see some bubbling in the glaze because the clay body started to bloat. The coil and paddle clay bodies were quite varied, but much of it seemed to contain high amounts of organic matter
More bowls. One in a light clay body, the other much darker. Again, vitrified and hard. All of the trimmed pieces I found were trimmed with an economy of movement. There is no wasted time in the trimming here.
Detail of another foot. Gorgeous clay, and lively trimming.
Interior detail of bowl directly above. Note the beautifully folded over and compress lip of the piece stuck to the inside here, and the glaze window.
Paddled Chosen Karatsu flask. I wish I could get those blues!
Detail of flask neck.
Detail, lip.

Overglaze tests with iron pigment

Here is the original test cup (r), and one pulled from the last firing (l). The first cup was refired to cone 5, the second to cone 6. I was worried with the extra heat that the overglaze brushwork would bleed or run, but it didn’t.  
One thing I like about this overglaze deco is that it allows me a ‘second chance’ for decoration when refiring this kind of work. The other is that it allows for finer detail showing up in the final product. Underglaze iron tends to get absorbed into the glaze and/or clay body, so the finest lines become obscured or transparent.

PINCHING BALLS…

…is one of my favorite ways to make cups. 

Often, during a cycle of making new pots I’ll end up stuck. New design ideas don’t pan out, or I dont have the techinical skill to make what I want. 

Rather than sit suspended in frustration, I’ve found it is useful do something familiar for a day or two. This usually clears my mind for fresh ideas, because I don’t need to concentrate so hard on familiar processes. Even better, I have something to show for a days work. 

Pinching balls into cups and bowls was the first thing I learned from my mentor, and these things are still some of my best sellers.  The process is simple and efficient, and can be easy or difficult depending on the clay. 

Getting ready for Yakimon Matsuri

This Golden Week (4/28 – 5/6) is the 6th annual pottery festival in Karatsu. It is always fun to show and sell, but getting ready can be a pretty busy time. 

This year I want to show some new designs, items I’ve never made before and/or sizes I don’t normally make. I’ve made some pedestal platters, coffee droppers, and a style of tokkuri that was popular at a show this last fall.  The general theme will revolve around rim carving and brush decoration of shrimp, and English letters written to look like Japanese kana script. 

Many people tend to think that Japanese dishes are small and numerous, and this is not incorrect, but for home use a popular size is a bit larger, around 7-8 inches (7 sun) or even a bit larger. I find that dishes this size get the most use around our house as well. 

Here’s the damage from this afternoon:

Carved rims
Waiting to be carved
Various 24cm plates
Shrimp chopstick rests

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.