Mumyoi Yaki in Sado Island
Have you ever heard of "Sado Island" in Japan? This island belongs to Niigata Prefecture （新潟県) and it is located in the Japan Ocean. It is an island formed by the active underwater volcano and it has been in existence for many years.
Clay from the gold mine
Sado Island is historically famous in Japan for one reason: the Gold. It is known as "The Island of Gold".
During Edo Era, Sado Island had produced massive quantity of gold. The total length of mining tunnel leading to the gold mines to is estimated to be about 400km. The gold was discovered in 1601 and it was shut down in 1989. During this period, this gold mine had produced 78 tons of Gold and 2330 tons of Silver. It was the major source of revenue for the Tokugawa government.
Mumyoi Yaki is a traditional craft of Sado Island (佐渡島) in Niigata prefecture (新潟県）. The Sado gold mine produced not only gold, but silver as well, and most importantly, it has natural clay with very high percentage of iron. Long time ago, the red clay collected from the gold mine was used as a medicinal concoction. It was applied to the wound to stop bleeding.
The medical practice to use the red clay to stop bleeding was originated in China. In 1596, when a Chinese medical doctor (李時珍) re-organized the Chinese medicine book (本草網目), he realized that no suitable name was given to this "red clay". He had tried to think hard for its name, yet he could not get a suitable name. Finally, he named it as Mumyoi (無名異), which means "Unknown".
During Edo era, Japan was also importing the "Mumyoi Medicine" from China. As they found Sado red clay posses the same properties, it was also named as Mumyoi. The clay ware made from this clay was called Mumyoi Yaki (無名異焼).
The history of Mumyoi Yaki
In 1819, a man named Ito Kanbei (伊藤甚平) started to use the by-product of gold mine to make Raku Ware (楽焼). In 1857, the pottery in Sado Island was further developed by Ito Tomitaro (伊藤富太郎). At that time, red clay was partly used. It was mixed with other clays to get a specific character of Raku Ware.
The red clay produced in Sado Island is called Mumyoi Yaki (無名異焼). A revolution in Mumyoi Yaki was made by the first generation of Miura Jozan (三浦常山). He studied the art of Yi Xing tea pot, and developed his own firing method using mumyoi red clay. There was only a handful of artists who specializes in Mumyoi Yaki, nevertheless, they have managed to achieve acclaim and recognition by obtaining two National Living Treasure (人间国宝) awards; the first award in the history of Mumyoi Yaki was given to Miura Koheiji ( 三浦小平二）, son of the 3rd generation of Miura Jozan, while the second award was given to Ito Sekisui (伊藤赤水).
The reason why Natural clay performs better in taste
Once you visit any Chinese, Taiwanese or Japanese tea shop, you would see many tea pots in red color. Generally we call it "red clay teapot". Most of the red-color teapots available in the market, perhaps more than 99% are made of artificially blended red clay. To obtain the red color, iron powder is added. It is very common and standard practice in pottery line.
Those artificially made red clays are not harmful to our health and its color is very similar to the color of natural red clay. However, it doesn't perform in the same way. In fact, its performance is nothing compared to that of Natural Red Clay teapot. It is hard for us to tell the difference between artificial 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 difference is the physical property. In natural red clay, the minerals exist in granule-crystal form and it has higher melting point. Ground iron particle that is added in artificial red clay has much lower melting point. Usually the melting point of artificially added iron oxide is at around 600-700 degree C, while the melting point of natural iron crystal is at around 1200-1300 degree C. Usually clay teapot is fired at 1000 degree C or even higher temperature; artificially added iron granule will be melted during firing process.. Because of the above reason, the natural clay has much higher porosity. Naturally the number of mineral ion being released from the clay is greater and it has more influence on the water quality.
It is said that Mumyoi teapot becomes very shiny after using it for some time. When it is well-seasoned, you can actually see your reflection on its surface. After being heated, the red clay shrinks to more than 30%; the gaps between the clay structure is compacted and are very close together. It easily traps substances from tea and thus forming a very shiny surface. Many customers describe that the texture of Mumyoi teapot is as smooth as silk.
There is another important process which contributes to this fine texture of Mumyoi teapot. The process is called "Namamigaki". It is carried out after teapot is partially dried at room temperature. The surface of the teapot is pressed by rods or stone to smoothen and harden its surface. This process is the most time-consuming work but it makes the surface of the clay very solid and tight. Even the "Namamigaki" expert can only complete 5 teapots in a day. Each teapot requires at least two times of "Namamigaki" process. Most tea pot artists have exceptional skills in producing high quality tea pots and they are rapidly becoming a rarity. In Sado Island, two artists were awarded the Living National Treasure of Japan and it is such a great honour. However the number of Sado red clay artists is decreasing and they are aging. No doubt that they are in great demand. Obviously there is very less successor as well. It is very difficult to find artist who makes pure red clay teapot with back handle style. Sadly many of them use Sado red clay as the base clay to produce glazed teapot or celadon ware.