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Bizen ware clay development: Bizen clay


Part of the charm of Bizen ware is in its rugged, earthy color. While other ceramic wares are died flashy colors, Bizen ware competes by using the natural color of its raw materials.


For that reason, the clay used when making Bizen ware is critical to professional potters.


There is a saying that Bizen ware is “(1) Clay, (2) Firing, and (3) The Potter’s Wheel” — this means that the most important element in Bizen ware is the clay. As the quality of a work differs depending on the clay, the development of clay has been a perpetual topic of attention with Bizen ware.


Types of clay
In the area around Inbe, Bizen City, Okayama, clay suited to Bizen ware is harvested in abundance. Yamatsuchi, or “mountain soil”, harvested from the mountains, and hiyose, or “field soil”, taken from beneath rice fields, are the primary kinds of soil harvested.


Yamatsuchi is the sedimentary clay dug up from weathered volcanoes in the surrounding area, while on the other hand, hiyose is the clay taken from beneath rice fields where the yamatsuchi accumulates when it is washed away by rainwater. Bizen ware essentially uses hiyose, which is mixed with yamatsuchi or other kinds of soil. In some cases, clay known as kurotsuchi, or “black clay”, is also mixed in.


Bizen ware, having made its appearance in the Kamakura Period (1185-1333), made use of yamatsuchi until the first half of the Muromachi Period (1336-1573). Yamatsuchi is low in iron and contains some gravel, which is why if you take a look at Bizen ware made in the Kamakura Period, you will notice some pebbles protruding from the surface of the pottery. Since it has few organic substances, yamatsuchi does not exhibit much color.


In contrast, hiyose has been the main type of clay in use from the Azuchi-Momoyama Period (1573-1603) to modern times. The black and highly viscous hiyose is said to be the best suited clay for Bizen ware.


In comparison to yamatsuchi, hiyose is inferior in terms of heat resistance, though, since it contains a large amount of iron and organic substances, it gives off bright colors when fired. The earthy color of Bizen ware is a result of this hiyose clay. Since it is clay taken from the town of Inbe, it is perfect for Bizen ware. Consequently, clay taken from the rice fields of other regions cannot be used to make Bizen ware.


Clay development
When making Bizen clay, first dug up soil is piled up in a field and left outside for two to three years. By being exposed to wind and rain, pebbles and impurities in the soil are removed.


Next, it is dried and clumps of the soil are crushed up into finer particles by a machine. Water is then added to break it down and it is run through a sieve to take out bigger pebbles, wood scraps, etc. The moisture is then wrung out and the soil is kneaded over and over again. Clay made in this manner is then set aside for an additional three years or so. The soil becomes even higher in quality as the result of microbes.


As such, a number of years are required in order to create clay that is ripe for use. When actually making Bizen ware, the air in the clay is released by meticulously kneading the clay by hand and foot, since, if there is any air inside when fired, the trapped air expands and can cause the pottery to break easily.


Many of these processes are now mechanized; however, being over-reliant on machines can cause inconveniences like losing essential elements from the soil. Soil development is therefore quite important.


If the properties of the soil differ, the texture of the finished Bizen ware will also be different. The quality level of soil that can be made is key to Bizen ware.

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