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HOME >Japanese Tea Pot > Mumyoi
Mumyoi Yaki is a traditional craft of Sado Island (佐渡島) in the Nigata prefecture (新潟県）. Sado Island used to produce huge quantity of gold. Most Japanese associate Sado Island with its gold mine. The Sado gold mine not only produces gold, but also siliver and the most importantly red clay that contains a very high percentage of natural minerals granule. A long time ago, the red clay collected from the gold mine was used as a medicinal concoction. It was applied to the wound to prevent from bleeding.
In 1819, a man by the name of Ito Kanbei (伊藤甚平) began making Raku Ware (楽焼) using the by-product of the gold mine. In 1857, the pottery in Sado Island was further developed by Ito Tomitaro (伊藤富太郎). At that time, red clay was partially used. It was mixed with other clays in order to get a specific character of Raku Yaki.
A revolution was created by the first generation of Miura Jozan（三浦常山).He developed the method using pure red clay. He studied the art of making China Yi Xing tea pots and came up with the present style of the red clay baking method. The red clay produced in Sado Island is called Mumyoi Yaki (無名異焼). Despite the Mumyoi Yaki has only a handful of artists who specializes in this craft, they have managed to achieve acclaim and recognition by obtaining 2 National Living Treasure awards; a first in the history of the making of Mumyoi Yaki tea pots was Miura Koheiji ( 三浦小平二）who is the son of 3rd generation of Miura Jozan and Ito Sekisui (伊藤赤水）
In an ordinary tea shop, you would see a number of tea pots in red color. We call it “red clay teapot” in general. However those “red-color clays” are different from what I call natural red clay (天然朱泥). Most of the red-color teapots available in the market, perhaps more than 99% are made of synthesized red clay. The red color was produced with an addition of iron particle into the clay. Those artificially made red clay are also red, and of course not harmful and very similar to the color of natural red clay, yet it doesn’t perfrom in the same way. In actual fact, it is nothing compared to the Natural Red Clay teapot but in appearance only.
It is hard for us to tell the difference between synthesized red clay and natural red clay just based on its outlook. Both artificial red clay and natural red clay contains a similar level of iron. The natural red clay contains not only a high percentage of iron, but other kinds of mineral as well. In natural red clay, the minerals exist in granule-crystal form that is made during natural re-crystallization. Thanks to the special granule structure and unique mineral composition, Sado red clay can stand very high baking temperature. Once the clay is baked at very hight temperature (1220-1230 degree C), it shurinks more than 30%, it becomes very high density, porous and gives a high insulation effect as well as high rate of reaction to the water structure.
The natural crystal has very special property. For example, diamond and charcoal is both made of carbon. But both substance carries different physico-chemical property. As it is, once mineral get crystallized, it shows big difference in melting point, hardness, shape and so on. Ground iron particle that is usually added in artificial red clay shows much lower melting point than naturally recrystallized iron granule that makes clay high temperature resistible. With higher temperature in baking, clay shrinks more than 30% that increase not only density but also the complexity of suface.
Sado red clay consist of 2 kinds of red clay.
A. Red Color Clay: Similar clay as Hon-ni(紅泥) of Yi Xing
B: Yellow Color Clay: Similar clay as Banko clay and Chu-ni(朱泥） of Yi Xing
In fact, the term "red clay" is referring to the color of clay after baking. However crude clay material does not always appear in red color. It appears in between red to yellow. The intensity of color is depending on the percentage of iron. The more iron it contains, the darker color it becomes.The photo below is showing the typical crude clay that consist of yellow and red clay. Although both clay becomes red color after baking, the property seems different. 
This photo was taken at the clay mine of Shimizu Ken located deep inside Sado mountain. It consists of red and yellow color clay.
Have you ever heard of “Sado Island” in Japan? The island belongs to the Niigata Prefecture and is located in the Japan Ocean. It is an island made from active underwater volcano and has been in existence for many years.
Sado Island is historically famous in Japan for only one reason. It is known as “The Island of Gold”. During the Edo Era, Sado Island had produced massive quantities of gold. The total length of mining tunnel leading to the gold mines to is estimated to be about 400km. It is no doubt that Sado Island keeps producing natural red clay. The gold mine was discovered on 1601. It was shut down in 1989; it produced 78 tons of Gold and 2330 tons of Silver. It was the major source of revenue for the Tokugawa government.
The mine produced not only gold and silver, but also red clay. This red clay is called Mumyoi Yaki (無名異) or Sado red clay. It is formed in a layer of 4cm in the gap of Quartz rocks. The red clay contains a lot of oxidized iron and other types of minerals.
Due to the extremely high mineral content, Sado red clay had been used as a medicinal remedy which was applied to heal wounds. In particular, it was very effective in stopping excessive bleeding. During the Edo Era (江戸時代）, Chinese medicine was sought after as Japan was not influenced by the West. At that time, Chinese medicine was called “Mumyoi”.
The particle size of Sado red clay is very fine. In addition, the baking temperature of Sado red clay is very high at around 1220-1230 degree C. With the high temperature, the clay shrinks a lot; as much as 30% or more which is similar to the character of the purple clay. As a result, the product has a very high density that gives a remarkable insulation effect and large surface area.
Mine is locked for safety. Even at the entrance, there are various kinds of clay exposed. The rocks in red color is the crude red clay.
In China, the natural red clay was used as a medicine to stop bleeding. In 1596 when a Chinese medical doctor 李時珍 re-organized the Chinese medicinebook 本草網目, he realized that there was no suitable name for this “red clay”. He had tried to think hard for its name, yet he could not get suitable name. Finally, he ended up referring to it as Mumyoi (無名異) which means “Unknown”.
Go to the Mumyoi Page Appears in 本草網目 in Chinese >>
During the Edo era, Japan was also importing the “Mumyoi Medicine” from China. As they found Sado red clay has the same properties, it was also named as Mumyoi and the clay ware made of the particular clay was called Mumyoi Yaki (無名異焼).
Beside Sado Island, there are a few more historically famous gold & silver mines in Japan.
There is an interesting fact. According to the record, Izu Gold Mine (Shizuoka Prefecture, Izu Peninsula) and Iwami Silver mine also produced red clay called “Mumyoi”. In particular, Iwami was also producing red clay ware. Unfortunately the Ishimi has stopped making red clay ware since their red clay was no longer available.
People often talk about “clay made of volcano”. In fact, it is nothing special if you know about the relationship between volcanoes and mineral forming. Good clay is always extremely rich in minerals.
Do you know where those minerals have come from?
They are produced by the volcano. Gold mine is made out of the volcano. When lava is coming up from the ground, it carries a complex of minerals dissolved in hot water. While it is slowly cooling down, minerals re-crystallized in between the gap of rocks (Quartz).
Similar to Sado Island that is made of underwater volcanoes, Japan has a number of volcanoes scattering over the country. As a matter of fact, Japan is a very ideal island to produce the fine clay for tea pot. In addition, there also exists a big chance to discover much more gold hidden somewhere in the mountains. ?
Using Sado red clay tea pot, the brewing temperature is very high and thanks to the mineral released from clay, water structure becomes smaller size. It enhances the flavor of oolong tea which is beyond anyone’s imagination. It was a new and surprising experience.The flavor of oolong tea brewed with Sado red clay was so sharp and pure.
Sado red clay teapot is suitable for all kinds of tea. However the effect of Sado red clay teapot may be particulary outstanding when it is used for fermented tea. For green tea, yellow tea and puerh ripe tea, some customers prefer purple clay teapot as it increases flavor even more than red clay teapot. The difference between purple clay teapot and natural red clay teapot is that purple clay obviously reduces aroma, yet drastically increases flavor. As for Sado red clay teapot, it increases flavor while it maintains the aroma.
Based on our experience, Sado red clay teapot performs outstandingly well on white tea, oolong tea such as Taiwan oolong and Wuyi oolong, raw puerh both young and vintage.
It is hard to say which is better between Sado red clay and Yi Xing red clay. Even in Sado, there are many different kinds of red clay, some gives better effect and some, less. Since the baking method is almost the same, the effect is depending on the iron content and the number of other minor mineral. I have genuine Yi Xing red clay that gives better effect than Sado red clay. I also come across with genuine Yi Xing red clay that gives the same effect or less than Sado red clay. In any case, Sado red clay gives a significantly stronger flavor than artificially mixed Yi Xing red clay.
It is said that Mumyoi Yaki will get shiny after using it for sometime so much so that you can actually see your reflection on it. Red clay shrinks to more than 30% after being heated and therefore the gaps between the clay structure is compacted and are very close together. It easily traps substances from the tea and thus forming a very shiny surface. In addition, there is another important process which contributes to the fine texture of Mumyoi which many customers describe that the texture of the Mumyoi teapot is as smooth as silk. This fine texture is produced due to the process called "Namamigaki". It is carried out after the teapot is partially dried at room temperature. The surface of the teapot is then pressed by rods or stone in order to harden its surface. This process is most time consuming but it makes the surface of the clay very solid and tight.
Sado Island is very isolated from the Japan mainland (Hon Shu). In fact, not many Japanese know of the existence of the Sado Red Clay Tea Pot.
In Japan, the only place where you can find the Sado red clay tea pot is Sado Island itself. Despite its outstanding quality, Sado red clay tea pot was only sold in the island and not elsewhere. Ironically, Sado red clay tea pot is only sold as souvenirs to tourists who visit Sado Island.
There is another reason why Sado red clay is limited in Japan. Very few Japanese drink authentic oolong tea and other kind of semi and full fermented tea. If teapot is only meant for green tea, there are many more teapot in Japan such as Banko purple clay that performs quite well. The remarkable performance of Sado red clay has never been revealed until now.
Most tea pot artists have exceptional skills in producing high quality tea pots and they are rapidly becoming a rarity. The fact that Sado Island has produced 2 artists who were awarded the Living National Treasure of Japan is a great consolation.
However the number of Sado red clay artists is decreasing and they are aging. They are without a doubt in great demand. Obviously there is very less successor as well. It is especially difficult to find the artist who makes pure red clay pot with the back handle style. Sadly many of them focus on the glazed tea pot or celadon ware using Sado red clay as a base clay.
Sado Island is now applying for the World Heritage status. Once it is registered, the supply of Sado red clay may be even more critical.
Zisha is always the ideal clay for Chinese teapot collector. But not many people are aware of what Zisha is.
Zisha in Chinese is "purple sand". Zi means purple and Sha means sand. The point is that Zisha does not mean "purple clay". It is called "sand" as most of clay in Yi Xing exist as crude rock. It is crushed and fermented for a few years on order to increase viscosity. Due to its low viscocity, Zishait is described as "sand" In short, the term of Zisha is referring to "Rock".
I used to wonder why Zhisha is meaning about purple sand despite is contains red and gree clayin addition to purple clay. The answer is smple if you have ever seen the Zhisha rock. It looks literaly in purple color. The rock contains iron that exist sometimes as hematite (red color), but most of time is the mixture between hematite and magnetite (blue-black). As the result, the surface of clay looks exactly in purple.. Zhisha is the name given for the rock due to its appearance. It is not precise to say "Zisha Teapot".
It is know that Yi Xing Zisha consist of 3 different clay, red clay, purple clay and green clay. Red clay and purple clay is very smilar. With higher
percentage of iron (more than 20%), it is called red clay and purple clay contains usually less than 10%. Red clay undergoes oxidation baking (Fe2+: Hematite) and purple clay undergoes reduction baking (Fe3+:Magnetite ). If purple is baked in oxidation fire, it will be orange - beige. The dominant mineral in green clay is either copper or chromium, Green clay is only meant for decoration as it makes take of tea very flat.
To our suprize, most of rocks in Sado mountain is made of "Zisha". In Sado,you will see the rocks in purple color everywhere and no one even pay attention for it. Just like Yi Xing, Sado island has red clay, purple clay and of course green clay as well. People used to call Sado island as theIsland of Gold. For now, it is the "Island of Clay".
Watanabe Tozo (渡辺陶三) was born in 1939. He is coming to the age of 70. His father was Watabane Kokuzo（渡辺国三）who was also famous in the making of Mumyoi Red Clay tea pots. In 1981, a tea pot set of his was presented to the emperor of Japan. In addition to the emperor, the price of Japan has visited his workshop and stay there for a day to learn pottery from him.
He was also very in awere of the Yi Xing tea pots. Unlike ordinary tea pot artists of Japan, he traveled a great deal to Yi Xing, Korea and Taiwan. His tea pot making style was well influenced by those Chinese tea pots design, yet he has his own style.
His working place is located historically renowned place.
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