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Glazes and Glazing Techniques

Seto ware has a tradition of over 1,000 years. During medieval times, Seto ware was the only earthenware in Japan that used glazes. Throughout its 1,000-year history, potters in Seto have produced various types of potteries by adopting a wide variety of glazes and glazing techniques.
This page introduces typical glazes and glazing techniques used in Seto.

Kai-yu and Ofuke-yu (Ash glaze and Ofuke glaze)

Light green and light blue

Kai-yu and Ofuke-yu

Ash glaze, made from wood-ash, is the most basic glaze and has been used since the earliest days of pottery production in Seto. Its colors vary to some extent, depending on the ratio of impurities contained in the used ash. In general, however, the glaze turns light yellow green in oxidation firing, while it becomes light blue in reduction firing. Ofuke glaze, also made from wood-ash, was used at the kiln in Ofuke-maru in Nagoya Castle during the Edo Period for pottery production under the patronage of the lord of Owari Province.

Tetsu-yu (Iron glaze)

Brown, dark brown, and black

Tetsu-yu (Iron glaze)

Iron glaze uses iron oxide as a colorant. In Seto ware, iron glaze was first used in Ko-Seto ware toward the end of the 13th century (Kamakura Period). Depending on the amount of iron content, the colors of the glaze vary from yellow-brown to black. There are various types of iron glaze, including Seto black, tenmoku glaze, and Ko-Seto glaze.

Kiseto-yu ( Ki-Seto glaze)

Yellow

Kiseto-yu ( Ki-Seto glaze)

Ki-Seto glaze contains a little amount of iron and produces yellow-brown color. Toward the end of the 16th century (Momoyama Period), a potter in Seto moved to Mino (now Gifu Prefecture) and developed this glaze. Many potteries using this glaze have designs or motifs in green, the color of which is produced by copper sulfate.

Oribe-yu (Oribe glaze/copper red glaze)

Green/red

Oribe-yu (Oribe glaze/copper red glaze)

Oribe glaze uses copper sulfate as a green colorant. Since the glaze was favored by Furuta Oribe, one of the leading followers of Sen-no-Rikyu, it is known as Oribe glaze. During the early 17th century (Momoyama Period), a potter in Seto moved to Mino and developed this glaze. While copper produces green (Oribe’s favorite color) in oxidation firing, the same material produces red in reduction firing.

Shino-yu (Shino glaze)

White

Shino-yu (Shino glaze)

Shino glaze, primarily comprised of feldspar, produces a shiny milky white color. Toward the end of the 16th century (Momoyama Period), a potter in Seto moved to Mino and developed this glaze.

Seiji-yu (Celadon glaze)

Blue and green

Seiji-yu (Celadon glaze)

Containing a small amount of iron oxide, the glaze produces either blue or green color. Potters in Seto began using the glaze in the early 19th century (Edo Period), when production of porcelain was initiated in Seto. Its use became particularly widespread during the Meiji Period (1868–1912). Potters in Seto also produces chromium celadon, which uses chromium as a colorant.

Ruri-yu (Ruri glaze)

Dark blue and indigo blue

Ruri-yu (Ruri glaze)

This glaze, containing gosu (cobalt blue pigment), produces dark blue color. Potters in Seto began using the glaze during the early 19th century (Edo Period), when production of porcelain was initiated in Seto. Owari Province, however, once banned the use of the glaze because the cobalt blue pigment was extremely expensive. After the Meiji Period, the glaze became popular for producing charcoal braziers and flower pots.

Diverse Decoration Techniques

Potters apply diverse decoration techniques, ranging from painting with pigments to engraving and pasting clay on the surface of the ceramic bodies, deforming body shapes, and glazing in various different ways. Combinations of multiple techniques can further add complex features to ceramic products.

Decoration on the surface of potteries

Inka

(stamped decoration)

Inka refers to a decorative technique in which a pattern is stamped on the surface of wet clay object using a mold with incised design. The oldest example of applying this technique is an item of Ko-Seto ware, which was produced during the Kamakura Period (12-14th century).

Kakka

(incised decoration)

Patterns are incised with a tool, such as a plane and spatula, on the ceramic surface while it is leather-hard. This technique is also known as shizumibori (lit. sinking engraving).

Choka

(applied decoration)

The same clay as the body is fashioned into design motifs in molds and applied on the slip-covered surface of the leather-hard ground.

Ukashi or Ukibori

(relief carving)

This is a sculptural technique in which a form is carved in relief on the surface.

Kushigaki

(parallel line decoration)

A comb-like tool is used to engrave a pattern comprising multiple parallel lines.

Zogan

(Inlay)

After a pattern is engraved on the surface, clay of a color different from that of the body is inlaid.

Decoration by using glazes

Kesho or hakeme

(brush mark varnish)

White slips and other materials are applied on the surface of the body.

Kakiotoshi

(scraped-off decoration)

The clay of a different color is applied over the ground of a contrasting color, and then the pattern is cut through the applied clay with a tool. The clay is then scraped off to reveal the surface beneath.

Kakewake or nagashikake

(pouring multiple glazes)

Glazes of various different colors are poured on the surface so that the spontaneous flow of the glazes will create a design.

Bokashi or fukizumi

(spray decoration)

A glaze is applied over the surface using a brush or spray to add shading to the color.

Itchin

(slip trailing decoration)

Itchin is also known as moriagete. Pigments of high viscosity are trailed over the body using a cone with a narrow metal nozzle. The design pattern is raised in relief by trailing the pigments.

Decoration of the body

Rinka or ryoka

(crespina)

Petal-shapes are created by concaving several spots along the lip at regular intervals or adding lines on the body.

Mentori or herame

(chamfering)

The spherical surface is scraped off by spatula to make the spherical body into a polytope.

Kutsu-gata

(shoe-shape deformation)

The ceramic vessel is deformed into an irregular elliptic shape by applying force from the rim to the body.

Sukashi

(openwork)

The design motifs are cut out.

Other

Nerikomi

(marbleized ware)

Different colored clays are lightly wedged together to give a marbled effect.

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