Raku ware
It is traditionally characterised by being hand-shaped rather than thrown, fairly porous vessels, which result from low firing temperatures, lead glazes and the removal of pieces from the kiln while still glowing hot.
In the traditional Japanese process, the fired raku piece is removed from the hot kiln and is allowed to cool in the open air.
The Western process can give a great variety of colors and surface effects, making it very popular with studio and amateur potters.
The resulting tea bowls made by Chōjirō were initially referred to as "ima-yaki" ("contemporary ware") and were also distinguished as Juraku-yaki, from the red clay (Juraku) that they employed.
Toyotomi Hideyoshi presented Jokei, Chōjirō's son, with a seal that bore the Chinese character for raku ("Enjoyment").
Both the name and the ceramic style have been passed down through the family (sometimes by adoption) to the present 16th generation (Raku Kichizaemon XVI).
In Japan, there are "branch kilns" (wakigama), in the raku-ware tradition, that have been founded by Raku-family members or potters who apprenticed at the head family's studio.
Other famous Japanese clay artists of this period include Dōnyū (grandson of Chōjirō, also known as Nonkō; 1574–1656), Hon'ami Kōetsu (1556–1637) and Ogata Kenzan (1663–1743).
Although he continued to experiment with raku firing for a few years following his return to England in 1920, the technique was largely forgotten after the 1930s.
These patterns and color result from the harsh cooling process and the amount of oxygen that is allowed to reach the pottery.
[5] Water immediately cools the pottery, stopping the chemical reactions of the glaze and fixing the colors.
These effects are created by placing horse hair, feathers, or even sugar on the pottery as it is removed from the kiln and still extremely hot.
[9] It is important for a kiln to have a door that is easily opened and closed, because, when the artwork in the kiln has reached the right temperature (over 1000 degrees Celsius), it must be quickly removed and put in a metal or tin container with combustible material, which reduces the pot and leaves certain colors and patterns.
Typically, pieces removed from the hot kiln are placed in masses of combustible material (e.g., straw, sawdust, or newspaper) to provide a reducing atmosphere for the glaze and to stain the exposed body surface with carbon.
The first Japanese-style kiln in the west was built by Tsuronosuke Matsubayashi at Leach Pottery, St Ives in 1922.
Therefore, kyanite is often the preferred material, as it contributes both mechanical strength and, in amounts up to 20%, significantly reduces thermal expansion.
The Japanese artists maintain that any work by other craftspeople should take their own name, (i.e., Soldner-ware, Hirsh-ware), as that was how "raku" was intended.
[11] Raku in the west has been abstracted and is now a more philosophical approach with the emphasis on the spontaneity of surface pattern creation rather than purely a firing technique.
"Reduction is incomplete combustion of fuel, caused by a shortage of oxygen, which produces carbon monoxide" (Arbuckle, 4).
These variables—which include wax resist, glazes, slips, temperature, and timing[16]—ultimately determine the outcome when firing a piece of clay.
[16] Raku glazes contain alumina, which has a very high melting point, so that they remain in place and are not replaced by carbon as the wax is.
Obvara is a raku form that uses a yeast solution that creates an earthy tone on secondary firing.
The obvara mixture, made from yeast, flour, sugar, and water, is usually opaque cream in color.
