PPP - Electric Raku
However, firing raku at home or in a small studio can be a difficult and even frightening experience. Pieces are fired to 1800 or 2000F, often in a gas-fired ceramic kiln, and are then carefully removed with long tongs and placed in the reduction atmosphere, usually a metal can or brick-lined area that contains the reduction materials. Many artists and potters who want to produce raku are fearful of working with gas and fire. It can be very intimidating to open the lid of a 2000F kiln or, worse yet, to pick up a red-hot firing chamber while trying to reach a piece inside. Additionally, the protective aprons, gloves and facemask often required for the conventional raku firing process are awkward and very uncomfortable to wear.
Recently, a new electric kiln* was developed that can make raku firing safer and easier. The kiln looks similar to a gas-fired kiln and is built of durable brick with a metal frame. However, instead of running on gas, the kiln plugs into a standard 120-volt/20-amp outlet. (Larger versions require 240 volts.) A hand-operated winch opens and closes the firing chamber, providing easy access to the pieces inside. An analog pyrometer and infinite heat control help ensure precise firing, and electronic controls can also be added. By using an electric kiln and specially formulated glazes, artists and potters can explore the enjoyment of raku without its conventional difficulties and hazards.
Using an Electric Raku KilnThe kiln should be located in an area with adequate space, ventilation and easy access to electric outlets. If possible, leave room to access the kiln from all sides. Make sure you remove any flammable materials such as curtains, plastics, etc., that are near the kiln.
If the kiln will be located outside, keep it dry by placing it under a roof or overhang or by covering it with a water-resistant tarp when it is not being fired. If the kiln will be located inside, place it on a cement floor to prevent the heat of the kiln from damaging the surrounding flooring materials.
An important part of the raku process includes having the materials ready and available before you begin firing. You will need reduction containers (galvanized garbage cans are best) that are the correct size for your ware and are arranged for easy access and clear movement around the kiln. Grass, leaves, sawdust or shredded paper all work well as reduction materials. These combustibles should be stored at a safe distance from the kiln, yet easy to reach during the post-firing process. Allow enough room for unencumbered movement, and make sure water sources are nearby for cooling and emergency situations.
Use only raku clay, and make sure it is bisque-fired before the actual raku firing. Raku clay has a high grog content, which minimizes thermal shock as rapid temperature changes occur. Non-raku clay can break and result in damage to the kiln and other pieces inside. Use raku or metallic oxide glazes when rakuing to achieve vivid raku colors in the reduction stage.
Begin heating the kiln on high with the firing chamber completely closed. The kiln might take two hours to reach raku temperature. As the kiln approaches approximately 1900F, open the kiln and begin loading your ware. To preheat the ware and avoid thermal shock, slowly lower the raku firing chamber. Maintain full power when opening the kiln to minimize heat loss between pieces.
At around 1900-1950F the rakuing process will begin to take place. Raku firing generally takes about 15 minutes—you can tell the ware is ready to remove when it has a shiny, wet appearance. Raise the firing chamber, remove the pieces with tongs and place them in your reduction containers as quickly as possible. Once the ware is inside the container, add more reduction materials. Be sure to fully cover the pieces within 15 seconds to ensure efficient reduction. (It is not how much reduction material you use, but how fast you can get pottery ware into the container and covered that provides exceptional raku pieces.) The heat from the piece will ignite the reduction materials, causing a reaction with the glaze. The result is a wide range of colors on the surface of the piece. Keep the container covered for 15 minutes to 1 hour or even longer, depending on the size of the ware and the desired effect. After the ware has cooled, wash each piece to remove soot and carbon.
Once ware has been removed from the raku kiln and placed in reduction containers, new items can be loaded in the kiln.
Unlike a conventional gas-fired kiln, which must be opened from the top or have the entire kiln drum taken off the base, the electric kiln minimizes heat loss when the firing chamber is lifted, so you can continue the rakuing process without interruption. The usual recovery time between pieces (i.e., the time required for each new piece to reach the required rakuing temperature) is just 15 minutes, compared to much longer recovery times in conventional gas kilns. To further reduce the recovery period, you can place the next items to be rakued on top of the raku firing chamber (on the outside) throughout the firing process, so that they will be preheated before they are placed in the kiln.
Finding the Right GlazesMany commercial glazes are available from numerous suppliers. Sometimes commercial glazes designed for decorative ceramics make excellent raku glazes. A glaze colored with metallic oxides such as copper, cobalt or tin works nicely and usually becomes green, blue or white when used in oxidation.
Different firing temperatures will also affect the final color. A white crackle raku glaze, for example, might create a beautiful white crackle when fired a cone 07; however, when fired at higher temperatures of cone 05 or more, the result will be a clear silver/gold color. A gold glaze may be gold when fired at cone 07-05 in a heavy reduction atmosphere, while in oxidation the color will vary from various blues to greens. And a copper red luster might be as copper as a penny in heavy reduction atmosphere (cone 07-05) but will achieve various blues and greens when oxidized. Experiment with different glazes and colors to find the ones that best meet your needs.
If you would rather make your own glaze, many good glaze formulas can be found in raku books, such as Raku, A Practical Approach, by Steve Branfman.** As with the rest of the raku process, experimenting is part of the fun.
Achieving HappinessThe variability and unpredictable nature of raku are the characteristics that attract many artists and potters to this unique art form. However, the raku firing process does not have to be part of this variability. With an electric raku kiln and the right glazes, you can easily and safely create beautiful works of art.
For More InformationFor more information about creating raku with electric kilns, contact Olympic Kilns, 4225 Thurmond Tanner Rd., P.O. Box 1347, Flowery Branch, GA 30542; (770) 967-4009 or (800) 241-4400; fax (770) 967-1196; or visit http://www.kilns-kilns.com.
*The electric raku kiln was developed and is supplied by Olympic Kilns, Flowery Branch, Ga.
**Krause Publications, Iola, Wis., 2nd Ed., March 2001.