Craftsmanship is about understanding the materials. [Listening to the voice of the clay. Sakusuke Kiln Column]

May 31, 2025

Seto City in Aichi Prefecture is a pottery production center with a history of over 1,000 years.
The reason is that "Frogme" is the best clay for pottery. This comes from the fact that a type of soil called "gairome" is extracted here.

Why is frog eye suitable for pottery?
Its main feature is its plasticity, which allows it to retain its shape like a shape-memory alloy, making it very easy to throw on a potter's wheel. It turns pure white when fired and is highly fire-resistant. If it is refined and the clay content is mixed with feldspar and silica, it can even be used to make porcelain clay.

It is truly a clay that was born for pottery. Thanks to this clay, pottery has been produced in Seto for over a thousand years. However, frogeye is a natural resource that is dug from the mountains, and as it is dug up, it disappears.

I would like more people to know about this and become more interested in it.
We spoke to people involved in the ceramic raw materials industry and potteries who work with clay in Seto.

*If you would like to know more about frog eyes, please click here .

This time we will introduce Sakusuke Kiln, a pottery manufacturer in the Akazu district of Seto City that has been in business since the Edo period. In order to preserve the traditional colors of Oribe and Kiseto ware, the clay is made from Gairome clay, and the glaze is made from natural ingredients based on natural ash.

The workshop, where the eye-catching "Akatsu tiles" that were once made in Akaatsu, is a space where you can see the original experience of making things that make use of Seto's clay. We spoke to Keishi Kato, the sixth generation head of the family and a holder of Aichi Prefecture's Intangible Cultural Property, about clay making and understanding materials in crafts.

What is Sakusuke Kiln?

Sakusuke Kiln is located in Akazu Town, in the eastern part of Seto City. Akazu Town was an independent village called Akazu Village until it was merged into the then Seto Town in 1929.

The present-day Akazu Town was apparently a bustling downtown area at the time, and is an area within Seto that is densely packed with kilns and pottery wholesalers. Even today, it has a different atmosphere from Seto's central city area, and the surrounding area itself feels like a pottery village.

In Akazu, Akazu ware, a type of Seto ware, is designated as a traditional craft.
Its origins date back to the Sue ware of the Nara period (around 700), and it is said that the full-scale technique of applying glaze was first used in Japan during the Kamakura period.

There are seven types of traditional glazes: Oribe glaze, Kiseto glaze, Shino glaze, Koseto glaze, Kaiyu glaze, Onofukai glaze, and Iron glaze. In addition, there are 12 decorative techniques, including spatula carving, flower printing, kushime (comb pattern), and Mishimade (hand-painted).

Among all of Akazu, Sakusuke Kiln stands out for its stately appearance. Descending from Toshiro, known as the founder of pottery in Seto, the family was founded by Kagemoto, the younger brother of Kato Riemon (the first Karasaburo), who served as the official supplier of Oniyaki ware to the Owari domain throughout the Edo period . During the Edo period, the family took the name Kato Sakusuke, and has continued to operate under the name Sakusuke Kiln to this day.

In this workshop, you can see the original landscape of craftsmanship that makes use of Seto's soil. The workshop is surrounded by buildings on all sides, and the wind is kept out so that the pottery can dry slowly. The courtyard is covered with grass, so that the pottery can survive even if it falls off while drying in the sun.

Around it are rows of raw clay storage areas and clay-making equipment. There is also a moro (workshop) where glazes are stored, and it is here that the clay-making process is completed.

The kilns are located in a building across from the site, and there are several gas kilns, coal kilns, and wood-fired kilns. The workshop is like a museum. You won't find another workshop in Seto that still retains so many traditional elements.

Keiichi Kato, the sixth generation head of Sakusuke Kiln , is a registered intangible cultural property holder of Aichi Prefecture ( Pottery (Kiseto and Oribe ).
His works are made with traditional Oribe glaze and Kiseto pottery. Oribe is characterized by its deepest green color , which was also loved by Kitaoji Rosanjin . It is said that the key to Kiseto is the balance between the matte pale yellow and the green aluminium .

To achieve these ideal colors, it is essential to create glazes based on natural ash, as well as to pay close attention to the clay. With use, the pottery develops more character and increases in value.

" Pottery absorbs water and continues to breathe even after it is completed. For this reason, it ages with use, but we Japanese are a unique people who find beauty in this, which we call 'wabi-sabi.' If we want to cherish this, then our commitment to the clay is an essential element."

Making clay for Sakusuke Kiln

At Sakusuke Kiln, they spend about a month once a year making the basic clay known as "motodo." We were shown the first day of this precious clay making process. The base clay is, of course, Seto's treasure, "Kaerume" clay.

"I think that Kame-do is the best clay for pottery in the world. That clay has supported Seto, and I think it is as valuable as a gold mine," says Keishi.

There are three reasons for this.

"First, it's highly fire-resistant, enough to make porcelain. Second, it's white. Iron and titanium are elements that give it color when fired in a kiln, but it's free of impurities in that sense. Third, it's highly plastic, making it extremely easy to work on a potter's wheel. It's so excellent that you can even use a technique called casting to make pottery."

This is a lump of frog-eye clay. When I asked Taniguchi, a craftsman who has worked at Sakusuke Kiln for over 50 years, which part is the clay, he explained to me in a straightforward manner, "This is the clay, this is the silica sand, and the shiny, bluish part is the frog-eye clay. It's the quartz that makes it glow." However, even among those working in pottery today, I think only a handful would understand this.

"It really should be more lumpy. If it has too much clay it hardens and becomes too stiff," he said with a look of regret. Compared to the past, there seems to be less and less good quality frog-eye clay available, so they continue to make improvements in order to maintain the tradition.

This is called a toromill, and inside it are stones called boulders that are rotated electrically to grind up the soil.

The clay is poured in from above. It is hard work. When the clay is being prepared, Takumi Inoue, a Seto Sometsuke ware artist, always comes to help out.

Add water and let it run for about 30 minutes. When you pour it under the tap, the raw clay breaks down and turns into a liquid slurry that comes out with force.

Once the clay is stored in the jar, it is squeezed out with a tool called a filter press to remove excess water, and the "motodo" clay is complete. This is then used as a base for further blending for Kiseto and Oribe.

"The reason is, to put it bluntly, if you apply Oribe or Kiseto to pure white clay, it loses its flavor. It ends up being too pretty, so I want to bring out the scent of the clay a little more. So, for Oribe, I add a small amount of red clay to add color. For Kiseto, I add even more red clay and increase the amount of chamotte to give it a rougher flavor. In a way, it's quite luxurious."

Behind the scenes of unchanging pottery

At Sakusuke Kiln, in addition to making clay, we also make glazes based on natural ash. As times change dramatically, we spend a lot of time creating the foundation that many people don't even realize.

" Having watched my father do it, I've always thought that was the way it was. However, nowadays we need to cherish this kind of traditional craftsmanship. People who can do this are in a very limited environment, and even if you want to start from scratch, it's quite difficult. I'm in a position where I can do it, so I want to continue."

However, Yuko, who always supports Keiichi as his wife and manager, says, "It's difficult to stay the same as before."

"Critics have told me that I'm still making pottery in the same way as my grandfather did. But now that it's difficult to get hold of the good quality clay we used to have, I'm struggling, not like a swan. Right now I'm doing my best to master our traditional craftsmanship, and to be honest, I don't have enough time," says Keishi.

"I think crafts are about understanding materials. A sense of affinity with materials that is born out of a dialogue with nature, within the Japanese sense of values. In the West, people try to control nature to suit their own will, but Japanese crafts encourage nature to take the form it desires. I want to return to the origins of Japanese crafts and then let new branches grow from them."

Perhaps it is truly about listening to the voice of the soil.

[Listening to the Voice of the Soil: Introduction to the Series]