About Mumyoi Joaka by Tozo Watanabe

Among the raw materials of Sado Mumyoi there is a special clay called "Joaka". It was recovered from the tunnels of the Aikawa gold mine, and its reputation among potters is close to legendary. This series is teaware made from 100% Joaka.

How Water, Kettles and Teaware Change the Taste of Tea

Tozo Watanabe

More about Mumyoi of Sado Island

What Mumyoi is

The red clay found around the Aikawa gold mine and in the Osado and Kosado mountain ranges on Sado Island is called "Mumyoi". Mumyoi pottery is made from that red clay, and it is the ware Sado Island is known for.

Joaka, the clay that barely exists

Raw Mumyoi Joaka clay

Alongside the clay called Mumyoi there is a special clay known among Sado potters as "Joaka".

It is said to be the clay Jozan Miura I and others used in their work, and potters regard it as the finest material available.

Jozan Miura noticed that the red clay from the Sado gold mines was very close in character to the clay of Yixing in China. By studying Yixing clay, firing and design, he laid the foundations of Mumyoi as it exists today. (His line later produced a Living National Treasure.)

Joaka is the name for clay recovered from inside the gold mine.

The clay itself has the same basic character as the red Mumyoi clay dug in the Osado mountains and elsewhere, and because it was filtered as it seeped through the walls of the mine, Joaka is made up of far finer particles than ordinary Mumyoi.

Joaka, in other words, is clay filtered by natural rock.

The red clay called Mumyoi, dug in the Osado mountains and similar places, generally has coarse particles and low plasticity, and cannot be thrown on the wheel on its own. Sado Mumyoi is therefore made by blending that red clay with a set proportion of the yellow clay called Nosaka.

Joaka, refined naturally as it passed through the rock walls of the tunnels, has a very fine particle size and can be made into a teapot on its own.

Mumyoi Joaka lifts the aftertaste and the richness

What defines Joaka is that it is dug inside the tunnels of the gold mine, and that its particle size is fine.

Fine particle size matters a great deal for teaware. Finer particles mean the piece can be fired dense at a lower temperature.

Fine mineral particles also make the teapot more porous, which increases its surface area and with it the effect on taste.

Mumyoi clay is becoming scarce

When the Aikawa gold mine was still working, Mumyoi clay was also taken from inside the mine.

Now that every mine has been closed, Mumyoi potters dig the clay at their own sites in the Osado mountains and elsewhere, refine it themselves, and use it in their work.

Tozo Watanabe, the potter HOJO works with, had his own site and arranged the digging himself.

A few years ago the Agency for Cultural Affairs began a campaign to have the Aikawa gold mine listed as a World Heritage site. Digging for Mumyoi around Aikawa has been prohibited since, and Aikawa Mumyoi clay is becoming very scarce.

Mumyoi Joaka was dug inside the tunnels themselves, so the chance of obtaining more of it is very low.

The Aikawa gold mine on Sado Island

A sealed tunnel

Mumyoi Joaka finally goes on sale

Scarce as it is, the Mumyoi potter Tozo Watanabe holds a limited quantity of Joaka, which made it possible to produce teaware from this clay.

Over the past six months we made teapots under several sets of conditions, compared the taste, and went over firing temperature and the rest until the conditions we wanted were settled. That is what brought Joaka teaware to market.

Being able to make teaware from exactly the clay that was dug for Mumyoi in the Edo and Meiji periods is fascinating, and rather like a dream.

Mumyoi Joaka raises body, which brings out the aroma and the flavor of the tea. It suits fermented teas, mainly black tea and oolong.

Nama-migaki, a traditional technique that finishes only a few pieces a day

One thing that sets Sado teapots apart is a traditional technique called nama-migaki, or raw burnishing. Sado is the only teapot-producing area still doing it. There is more on the page below.

Nama-migaki, a traditional technique that finishes only a few pieces a day