Editing Raku ware (section)

==Kilns and firing==
[[File:Western-raku-vase.jpg|thumb|A western vase glazed and fired using the western raku technique, showing the soot, crackle glazing, and random [[reduction-oxidation]] typical of this pottery technique.]]

The type and the size of kilns that are used in raku are crucial in the outcome. One aspect that can affect the results is the use of electric versus gas kilns. Electric kilns allow easy temperature control. Gas kilns, which comprise brick or ceramic fibers, can be used in either oxidation or reduction firing and use propane or natural gas. Gas kilns also heat more quickly than electric kilns, but it is more difficult to maintain temperature control. There is a noteworthy difference when using an updraft kiln rather than a downdraft kiln. An updraft kiln has shelves that trap heat. This effect creates uneven temperatures throughout the kiln. Conversely, a downdraft kiln pulls air down a separate stack on the side and allows a more even temperature throughout and allows the work to be layered on shelves.<ref>Warshaw, Josie. The Practical Potter: a Step-by-step Handbook : a Comprehensive Guide to Ceramics with Step-by-step Projects and Techniques. London: Hermes House, 2003. Print.</ref>

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.

The use of a reduction chamber at the end of the raku firing was introduced by the American potter [[Paul Soldner]] in the 1960s to compensate for the difference in atmosphere between wood-fired Japanese raku kilns and gas-fired American kilns. Typically, pieces removed from the hot kiln are placed in masses of combustible material (e.g., [[straw]], [[sawdust]], or [[newspaper]]) to provide a [[Reducing environment|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.<ref>{{Cite web|url=http://www.studiopottery.com/cgi-bin/mp.cgi?item=9|title = Leach Pottery}}</ref>

Western raku potters rarely use lead as a glaze ingredient, due to its serious level of toxicity, but may use other metals as glaze ingredients. Japanese potters substitute a non-lead [[frit]]. Although almost any low-fire glaze can be used, potters often use specially formulated glaze recipes that "crackle" or craze (present a cracked appearance), because the crazing lines take on a dark color from the carbon.

Western raku is typically made from a [[stoneware]] clay body, [[bisque (pottery)|bisque fired]] at {{convert|900|°C|°F|abbr=on}} and glost or glaze fired (the final firing) between {{convert|800|-|1000|C|F}}, which falls into the [[Pyrometric cone|cone]] 06 firing temperature range. The process is known for its unpredictability, particularly when reduction is forced, and pieces may crack or even explode due to thermal shock. Pots may be returned to the kiln to re-oxidize if firing results do not meet the potter's expectations, although each successive firing has a high chance of weakening the overall structural integrity of the pot. Pots that are exposed to thermal shock multiple times can break apart in the kiln, as they are removed from the kiln, or when they are in the reduction chamber.

The glaze firing times for raku ware are short: an hour or two as opposed to up to 16 hours for high-temperature [[Pyrometric cone|cone]] 10 stoneware firings. This is due to several factors: raku glazes mature at a much lower temperature (under {{convert|980|°C|°F|abbr=on|disp=or}}, as opposed to almost {{convert|1260|°C|°F|abbr=on|disp=or}} for high-fire stoneware); kiln temperatures can be raised rapidly; and the kiln is loaded and unloaded while hot and can be kept hot between firings.

Because temperature changes are rapid during the raku process, clay bodies used for raku ware must be able to cope with significant thermal stress. The usual way to add strength to the clay body and to reduce thermal expansion is to incorporate a high percentage of quartz, [[Grog (clay)|grog]], or [[kyanite]] into the body before the pot is formed. At high additions, quartz can increase the risk of [[Glaze Defects|dunting]] or [[Glaze Defects|shivering]]. Therefore, [[kyanite]] is often the preferred material, as it contributes both mechanical strength and, in amounts up to 20%, significantly reduces thermal expansion. Although any clay body can be used, white stoneware clay bodies are unsuitable for the western raku process unless some material is added to deal with thermal shock. Porcelain, however, is often used but it must be thinly thrown.

Aesthetic considerations include clay color and fired surface texture, as well as the clay's chemical interaction with raku glazes.

In a craft conference in Kyoto in 1979, a heated debate sprang up between Western raku artists [[Paul Soldner]] and the youngest in the dynastic raku succession, Kichiemon (of the fourteenth generation of the "Raku" family of potters), concerning the right to use the title "raku". 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.<ref>{{Cite web|url=http://www.koryu.com/library/wbodiford1.html|title = Soke: Historical Incarnations of a Title and its Entitlements}}</ref>

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. Consequently, this has expanded its application from pots to sculptural ceramics.