The Bracker Raku Kiln is a lightweight and portable design for firing ceramic pieces in your own backyard. The kiln we make today was designed by Bill Bracker in the early 1970's utilizing the technology of ceramic fiber. The kiln is made by lining a cage of wire fence material and a metal garbage can lid with one-half inch thick fiber blanket. The fiber is then rigidized with a mixture of sodium silicate and water. The use of the fiber allows the ceramicist to have the insulating qualities of 2-1/2 inches of soft insulating firebrick, yet it is light enough that anyone is able to pick it up. A complete raku set-up would include the kiln, a burner, a propane tank, a pad of soft fire bricks (or an electric kiln lid or base), a posted shelf for inside the kiln, and tongs, along with the user-provided metal tub for water, a metal bucket or can for the raku tongs (which can be very hot after use) and a metal garbage can (with a lid) with reduction material. Setting up involves laying out the pad, posting the shelf on the pad, setting the pieces to be fired on the shelf, placing the kiln over the shelf and pieces, attaching the burner to the tank, placing the burner in front of the kiln's burner port, and lighting the burner.
PLEASE NOTE: This kit DOES NOT INCLUDE: a propane tank, kiln posts, garbage cans, or metal tubs.
First, firebricks provide an excellent way to post the first shelf. Cut two of the firebricks in half and use three of the cut half firebricks (2-1/2” x 4-1/2” x 4-1/2”) in a triangular formation. Second, the kiln’s atmosphere is easily controlled during the firing to modify the amount of oxygen your kiln load receives. The kiln is equipped with venting (or peep) holes directly above the burner port. These can be left open or plugged to oxidize or reduce the firing atmosphere. A bag of fiber scraps have been included with your kiln and can act as excellent peep hole plugs for this kiln. Third, the included burner is not a forced-air burner, so a good supply of oxygen to the burner head is imperative. The tip of the burner should be approximately 1/2” to 1” outside of the kiln, but you can also control the atmosphere and speed of firing by moving the burner slightly towards or away from the kiln. Initial firings in a cold kiln should take about an one hour and successive firings should take approximately 45 minutes, depending on the glazes you might use and how many pieces you are firing (a tightly-packed kiln load could increase the firing time).
The kiln is shipped with a bag of shredded paper inside. Not only does it provide crush resistance during transit without adding excessive shipping weight, but it can also be used as reduction material for your first firing. Also great reduction material: leaves, sawdust, excelsior, hamster/gerbil bedding, and pine needles. Your kiln was also packed with styrofoam packing peanuts. Do NOT use these for reduction material. In most cases (when you aren't using commercially available liquid raku glazes), raku glazes should be mixed dry, then prepared with water as needed for each firing session. This is particularly important in glazes with a high content of gerstley borate. Safety is of utmost concern when raku firing. Make all participants and spectators aware of the open flame and the layout of the raku set-up so that no one gets hurt. Also make them aware of the flurry of activity that will occur when the firing is complete and the pots are moved to the reduction material or water. A “dry run” of this is helpful in choreographing duties and requirements of the participants as well as making sure that reduction material and water is in a convenient location. An extra bucket of water on hand for safety is also recommended. We encourage you to experiment with how regular low-fire glazes work in a raku firing. Some will work great and some won’t, and you can only find out by testing.