Seto City in Aichi Prefecture is a pottery production center with a history of over 1,000 years.
The reason for this is that the best clay for pottery, called "Gairome," can be 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.
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 .
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This time, we will deliver Sojuen has been in business since 1953. Using a machine called a roller machine, painting by hand, and retro silkscreen printing, this pottery maker produces 20,000 to 30,000 pieces per month, using a combination of machines and handwork.
When you make this many pieces, it's inevitable that some will be what we call "flawed" products in Seto. They may even break.
Pottery cannot be burned even at high temperatures, so failed works become industrial waste. As the supply of kaerume clay decreases, recycled clay is essential.
Representative Keiichi Ishikawa visited various raw material stores, wondering if there was anything he could do with these items, and discovered that they could be recycled.
Sojuen , a blue and white porcelain manufacturer that has been in business since 1953
Sojuen is located in the center of Seto City. The workshop appears in just a few minutes' walk from the Seto Suehirocho Shopping Arcade in the city center.
When you visit, you will see the craftsmen always working efficiently and efficiently.
In the workshop, molding is done using a roller machine. This machine can make two different shapes at once, and can mold about 500 to 1,000 pieces of one type per day.
Just place the clay block and it's done in seconds.
This is a picture of veteran artisan Katsuko Ishikawa painting the porcelain by hand, using the traditional method. She paints the porcelain swiftly as it rotates at an incredible speed.
This is a retro silkscreen printing technique. It is a very simple printing method in which holes are made in a mesh plate and ink is dropped only into the holes.
They do a lot of OEM work for major restaurants, but they also sell their own original tableware brand, the " Modern Series ."
Since the company was founded, they have been making tea bowls in particular, so they are extremely easy to hold, and when you hold them you get a very strong feeling that this is it.
We also carry this product at Hitotsuchi.
About the soil at Sojuen
Since our founding, we have been using "porcelain clay," also known as "stone clay," as our clay. In addition, we use "reinforced porcelain," which is less likely to break.
Both are purchased in sheet form from Tsuchiya and then formed into rods using a vacuum kneader.
To go into a bit more detail about the ingredients, this clay is a blend of frog's eye, white clay, feldspar, kaolin, and alumina.
These are: Gairome clay is the clay extracted from the original Gairome clay. Shiroku clay is a rough-grained grade of Gairome clay with a rough taste. Feldspar is a mineral that is widely distributed and exists in large quantities on Earth, and it helps dissolve the clay when fired at high temperatures.
Kaolin is a clay whose main component is the mineral kaolinite. It is a raw material that is rarely found in Japan. It is said to have been named after the clay mined in Kaoling, near Jingdezhen, China's largest ceramics production area, which has been used since ancient times. It has a fairly high refractory property and low iron content, so its main characteristic is that it bakes white.
Alumina is a typical ceramic material.
In the case of reinforced porcelain clay, it is said to contain a lot of alumina, which increases its strength.
The clay is blended with these ingredients, and scraps called "kude" that are produced when molding by machine are added, then kneaded in a kneading machine and adjusted to a hardness that is easy to use with a roller machine. Clay can be reused as long as it is not fired, so it is clear that clay is reused as much as possible.
Won't the frog-eye clay run out?
"I've been working on houses for 15 years, and ever since I started, people have been saying that frog-eye clay might soon disappear. Then I realized that 15 years have passed! I was talking about this with Sawada (studio point), and there was no point in just speculating, so I started going to see the sites and ask questions.
As I continued my research, I learned that if nothing was done, the current mines would close in 10 to 15 years. However, new mine developments are being promoted and measures are being taken to make areas that could not be mined possible open up. I learned that it is because of these measures that the mines are still operating today."
In this situation, we had to deal with the approximately 6 tons of waste pottery that we threw away every year.
Soil can also be recycled if separated
"I used to think that it was something that had to be thrown away. There was nothing I could do about it. But when I asked Tsuchiya in Mizunami City, Gifu Prefecture, he said, 'No, it's possible to use it if you crush it. But you'll need to sort it.'"
After hearing that story, I changed my mind.
And Ishikawa-san I thought I'd try to do what I could, little by little, and started sorting the waste pottery that I had previously thrown away all together.
The products are separated into final firing products (glazed and fired), bisque clay, and sheaths, and if these are taken to Tsuchiya, they will be turned into clay again.
"If you think about it in a nutshell, separating it means that it can be recycled. Think of it as the same as household waste. With the problem of soil becoming harder to extract, it's definitely a good thing to do.
It's easy to just throw it all together, but that just means burying it in a mine. If in the future we can no longer extract raw materials and have to rely on imports from overseas, there will be exchange rate risks. In that case, it seems more healthy to recycle what can be recycled, even if it's just the products that are produced at your own place."
Currently, they have gone a step further and are not just collecting and taking away waste pottery; they are also trying to develop products using recycled clay.
"When you try to turn white waste pottery into something whiter, you end up needing extra frog eyes. If you use a lot of precious frog eyes, I feel like that's not a very good way to recycle. But if you use black or yellow clay, you can do it without using extra frog eyes, so I've learned that this can be done, and I'm working on product development."
In addition, a project is underway to use the recycled clay to create original products such as tea bowls.
They also plan to reuse molds as much as possible.
"We use molds to make our dishes, but we can only make about 100 pieces with one mold. The reason is that there is a difference of 1 or 2 mm between the first and 100th times. For commercial use, that alone makes the bowls either too small or too big. So, in the case of tea bowls, we change molds about twice a month. For bowls with lids, it can also make it difficult to close the lids."
With over 20,000 molds manufactured per month, molds are piling up one after another. These also become industrial waste, which was a headache. However, when I asked the staff at the transport company that delivers the molds, I learned that if I just keep the molds, they will take them for recycling.
"I didn't know that before either. I finally found out after asking around and researching. I'm currently working on a product using recycled clay, and I plan to reuse the molds that I've already used."
They plan to introduce a machine called a "water iron" that requires more manual labor than a fully automatic roller machine. If commercialized, it will be the first non-white vessel in the history of Sojuen.
"I want to increase the value of white tableware."
"As someone who makes white pottery, I want to raise the value of white pottery. Recycled clay doesn't have to be white. I would like to be able to present that value. If we want to pass on frog-eye clay to future generations, we have to do a lot of things."
The vessels are naturally white.
Is that really the norm?
And what can be done to prevent this precious clay from becoming industrial waste?
I hope this will give you a little something to think about.
[Listening to the Voice of the Soil: Introduction to the Series]
Part 1: From raw soil to clay. [Listening to the voice of the soil. Column on the Kasen Mine]
Part 2: "I want to leave the soil for future generations" [Listening to the voice of the soil: Column on Seto Hongyo Kiln]
Part 3: Craftsmanship is about understanding materials. [Listening to the voice of the clay. "Sakusuke Kiln" column]
Part 4: What happens when you bake clay? [Listening to the voice of the clay. Column by Miyama Pottery Studio]
Part 5: In search of the beauty of white and blue. [Listening to the voice of the soil: Shin Kiln Column]
Part 6: Don't turn it into industrial waste. Think about recycling soil. [Listen to the voice of the soil. "Soujuen" column]
Part 7: What kind of clay is used in ceramic dolls? [Listening to the voice of the soil. Column compiled by Seto Tougeisha]
Part 8: Are the raw materials for pottery and glass harvested from the same mountain? [Listening to the voice of the soil: A column from "Jinya Marusen Ceramic Raw Materials"]
Part 9: Clay making by a long-established clay company founded about 150 years ago [Listening to the voice of the soil. Column on "Maruishi Ceramic Raw Materials"]
