There are many ways potters can shape the "earth" they see. The most common is to throw it on a wheel or rokuro. Other ways include tebineri (hand-pinching), himo-zukuri (coil-building), tatara-zukuri (slab-building) or wari-gata (piece-molding).
Another technique is called kuri nuki, or carving out. The potter will take some type of tool and slowly whittle into the clay to search for a form. There's no throwing, pinching or coiling; just discovery by digging. The form is born from the clay more than created by the potter. See potter Wakimoto Hiroyuki for more.
High-fire clay. Sturdier than earthenware, and waterproof even without glaze.
Low-fire clay.Not waterproof; porous; must be glazed to be waterproof.
Flat horizontal disk that revolves on a pivot. A clump of clay is thrown in the center of the wheel, and shaped upwards with both hands (one on the inside, the other on the outside). Wheels come in various types, from the classical handwheel to the foot-treadled flywheel to the modern electric wheel.
Potters can mix metal oxides with water and apply this solution to the clay surface in varying amounts, then rub it off, to achieve various effects.
Tatakizukuri Paddling technique used to make Karatsu ware, in which strings of clay are stacked on a wheel. A wooden paddle is then used to "paddle" the outside into shape, while the inside is supported by battens. This technique likely originated in Korea.
- odo tsuchi
Wedging the Clay. Photo Courtesy of Suntory Museum of Art
In this section, we present some common clay terms and a brief overview of the clay production process.
Clay, called tsuchi in Japanese, dictates the "flavor" of the pot. The Japanese term for this is tsuchi-aji (literally clay flavor). Tsuchi-aji is of crucial importance for unglazed stoneware like Bizen, Shigaraki, and Iga. See photo examples at right.
The chemical composition of the clay gives each ceramic style its own special qualities and characteristics. Minerals like iron and magnesium fuse with the clay to provide different colors and surface textures, and combine with other factors -- like the type of wood used to fire a kiln -- to provide a unique style. Some of these styles are more porous, others are smoother, lending themselves to glazing. Even from within the same region, mountain clay and rice-field clay give rise to different qualities.
TASTING THE CLAY
Zanguri. Tea masters use the term zanguri to describe the distinctive quality of clay. It's a term of appreciation of the rough, unrefined style of potting that gives a piece a particular ambience. When you pick up a good chawan (tea bowl), you'll notice the rough, yet light and natural clay, which hasn't been glazed. In fact, it looks like it hasn't even been fired at all on some chawan. For Shino ware, the term zanguri is used in a special way to describe the soft appearance of the clay -- more specifically, clay that looks like it came out of the kiln unbaked. Some chajin (tea afficiados) say they can "taste" the raw clay of a Shino chawan. You can see that zanguri on the chawan shown in the above photo.
Shino ware in mogusa clay with rusty
red glaze and feldspar-glazed patches.
Work of potter Kobayashi Junko.
Ishihaze. Many potters prefer to remove the impurities of the clay before making their art. Some potters, however, like a rougher clay and leave in small stones that sometimes burst out on the surface during firing - called ishihaze (see photo examples at right).
THE PRODUCTION PROCESS
- Clay Extraction and Drying. Most Japanese ceramic styles are named after the region where they were first fired. The clay, too, nearly always comes from the same area (e.g., Shigaraki ware uses Shigaraki clay). Clay is also sold at auctions in Japan, so regardless of where a potter lives, he/she can typically buy clay from any region.
- Pulverizing and Sifting. The dried clay is broken up into small pieces (by machine) and then put through a sieve to remove impurities and capture only the finer earth. Stones and dirt are discarded. Some potters, however, intentionally leave in small stones to achieve the ishihaze effect (see above).
- Straining. The clay is next mixed with water, and the resultant mixture is filtered again in order to capture only the finest earth, which is then squeezed to remove the water, and then partially dried.
- Pugging. Clay is fashioned into a square lump, and put through a pug mill, which shapes it into cylindrical lumps.
Wedging. The clay is then wedged by hand to rid it of any air.
Drying. In last
photo, large drying
plates are given a
by being pressed
- Forming on Potter's Wheel. A clump of the clay is thrown in the center of the wheel, and shaped upwards with both hands (one on the inside, the other on the outside). The resultant form is then further refined using various tools.
- Drying, Finishing. The pieces are allowed to dry thouroughly, and then they are trimmed and finished. The pieces are again allowed to dry (several days).
- Bisque Firing. For pieces that will be glazed, the dried form is first bisque fired, making it easier to apply overglaze and improving the adhesion of color pigments during the main firing. For unglazed ware, the dried pieces are not bisque fired (jump to Step 10).
- Glazing. After bisque firing, the pieces are allowed to cool, and then glazed.
- Main Firing. Depending on the style being created, the pieces are now loaded into the kiln for only a few hours or for several days or for weeks.