Posted in Ceramics on May 5th, 2010 by admin
Beginning in the 1950′s, the onggi potters started to adopt a traditional Korean technique of refining clay that had hitherto only been used in the manufacture of high-quality white ware. Thus, the methods described below are essentially the same both for onggi and porcelain ware manufacture. About twenty years ago, some onggi workshops on Kanghwa Island adopted that technique, and its use spread gradually to Kyonggi and South Ch’ungch’ong provinces.
A field approximately 75′ x 75′ is used for the drying of clay. At each corner of the field a round hole approximately eight feet in diameter is dug out. These are settling vats. Today they are sometimes lined with cement. A smaller rectangular vat approximately two by four feet is built tangential to each of the circular vats. Small wooden connecting dykes allow water from each settling vat to flow back into the mixing vat as water is needed. Raised earth levies divide the ground between the mixing and settling vats into drying fields. In addition they serve as dry footpaths from which workers are able to remove the dried chunks of clay.
- Drying. The raw clay is dried in order to assure that it will slake more quickly in the refining vat. The clay is scooped up with a “three-men shovel” and piled in a sunny place to dry. It is then spread and evened with a wooden rake or hoe. Lumps of clay are broken with the hoe and large stones are picked out. The clay, in the form of soft shale, does not break or slake easily. The dried clay, broken roughly into lumps no larger than apples, is taken to the refining area in a basket or cart. Often an A-frame is used to carry about two hundred pounds to the mixing vats.
- Mixing and slaking. The clay is dumped from the cart or A-frame into the mixing vat containing water. After the clay has begun to dissolve in the water, it is stirred with a wooden paddle to which is affixed a handle with a cross bar at the end. The clay is levered up and down using the edge of the mixing vat as a fulcrum. The soft shale does not slake easily and a constant up-and-down motion of the paddle is necessary to partially dissolve the clay and produce a watery slip. The mixing process involves long and repetitive labor; women are assigned to this task since they can be paid less. To the Western observer it seems incredible that so much labor is expended on a process that could be accomplished easily and quickly by an electric blunger.
- Screening the clay. The thin slurry thus produced is scooped out with a bucket and poured through a thirty-mesh screen into the second or settling vat. The screening assures that clumps of clay, sand and pebbles do not enter the second vat. When more water is needed to continue the mixing process, that gate of the small dyke is removed. The relatively pure top layer of water from the second vat flows back into the mixing vat.
By repeated mixing, screening and return water flow the clay in the vat is eventually used up, leaving only stones and sand. These are removed with a shovel; more water and raw clay are added, and the process is begun again. Approximately a week is required to fill the settling tank with thick slurry. When the second vat has been filled with screened clay slip, it is scooped out with buckets and taken to the drying field, using the raised levies as walkways.
- Drying the slip to the plastic stage. The ground of the storage area is first covered with a layer of hemp or cotton cloth about 15′ x 15′ in order to prevent impurities from the ground getting into the clay and to facilitate removing it when it dries to a plastic stage. The clay slurry is spread on top of the cloth and the moisture in the clay is evaporated by the sun and wind. When the clay has been dried to a plastic stage, it is scored with a small scythe and the chunks approximately 12″ x 12″ x 6″ are carried to a cart, in which they are transported to the workshop.
- Further preparation of the clay. In the workshop the chunks of clay are stacked to form a rectangular mass approximately six feet in length, four feet in width and four feet high. Water is sprinkled on the clay and it is beaten with a long wooden mallet, first with he head, then with the side, by workers mown as saengjilggun. The clay that has been tacked on the workshop floor is then cut into thin slices about 1/8″ in thickness with a scythe-like knife. This part of the second processing is performed by workers known as ‘hardy lads” or “clay slaves.” The main reason for slicing the clay is to homogenize the distribution of soft and dry clay.The “hardy lads” next roll the clay into balls weighing forty or fifty pounds. In some workshops, a sheet of cotton cloth is laid on part of the workshop floor and the balls of clay are put on top of this; in others kaolin is spread directly on the earthen floor