Category Archives: clay

Let them eat cake

Here is my latest pot porn for you: freshly stamp milled, slaked, and filter pressed cakes of Izumiyama porcelain. 150kg. 

Not for the faint of heart, Izumiyama is hard to work with. It is non plastic and likes to crack during drying, impossible for slab work, and deforms easily. And it costs more than twice as much as Amakusa porcelain from Kumamoto. Most porcelain artists in Arita and Imari switched to using Amakusa porcelain long ago because it’s much easier to work with, doesn’t crack, and fires whiter. 

BUT! The beauty of Izumiyama in the wood kiln is absolutely undeniable. It fires to a soft ivory white and blushes in very subtle shades of peach. The surface is deep and translucent and vitrifies as low as around 1230C. 

Tomorrow morning first thing, Peter the Pugger will be getting a major workout!

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.

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!

Visiting the clay guy

I went to Shoukotoudo in Ureshino this morning to check out some of the new clay bodies they’ve been working on. Matsuo San, the owner, showed me some fired samples from a new body made to mimic the properties of the old Yamase clay. It looked so good I bought 135kg for testing. Really looking forward to playing with it. 

Here’s a picture of one of the machines in the factory, one ton batches!

And here is a freshly pugged batch, he was just feeding in the filter press cakes when I pulled up. 

And finally:

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:


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).