Raku is a fast, dramatic firing method in which glowing-hot pottery is removed from the kiln and placed in a container of combustible material. The result is often crackled glazes, metallic surfaces and blackened clay. It is a specialist process, usually done at studios, classes or events with experienced supervision.
What raku is
In conventional firing, the kiln heats and cools slowly with the door closed. In raku, the ware is pulled from the kiln while still glowing hot, then placed in a metal container with materials such as newspaper, sawdust or straw. The materials ignite, the lid goes on, and the limited oxygen affects the glazes and bare clay. This is called reduction.
Origins
Raku has roots in Japanese tea ceremony pottery, where hand-formed tea bowls were fired and removed from the kiln hot. The modern Western version, usually fired with the smoky post-firing reduction, developed in the 20th century, and American potter Paul Soldner is widely credited with popularizing that approach. Western raku differs from the Japanese tradition in several ways, so the two are not identical.
Step by step
This outline is for understanding only. Do not attempt raku without training.
- Bisque fire the shaped, dried piece in a standard kiln.
- Glaze with a glaze formulated for raku. Some pieces are left partly unglazed so the bare clay can blacken.
- Fire quickly in a raku kiln, typically gas fired, until the glaze melts. Target temperatures are often cited at around 1,600 to 1,850 degrees Fahrenheit, though they vary with the glaze.
- Pull the ware with long, heat-rated tongs.
- Reduce in a container with combustibles, then close the lid for a period, commonly 15 to 20 minutes though practice varies.
- Cool and clean the piece. Some potters cool in water, others air-cool. Scrub off soot to reveal the surface.
Clay and glaze
Raku involves rapid temperature change, so potters usually choose clay formulated to handle thermal shock, often with added grog. Raku glazes melt at lower temperatures than typical stoneware glazes. Some include metal oxides that create metallic or lustered effects. See pottery clay types and how to choose one for general information about clay bodies.
Raku ware is generally decorative. Surfaces are often porous and glazes may not be food-safe, so it is not usually used for eating or drinking.
Safety
Raku involves intense heat, open flame, smoke and fumes. Typical precautions include:
- Heat-resistant gloves, long tongs and protective clothing, including eye protection.
- Natural fiber clothing, which is less likely to melt than synthetics.
- A well-ventilated outdoor space, away from anything flammable.
- A respirator or proper distance from smoke, since reduction can release fumes.
- Supervision by an experienced raku potter.
Why raku costs more
Raku classes and pieces often cost more than ordinary pottery. Reasons usually include a dedicated kiln and fuel (compare ordinary pottery kiln costs), a supervised session, specialized gear, glazes and the number of pieces that crack or fail from thermal shock. Part of the cost is also the time and skill involved in running a firing.
Electric kilns and cone 6 clay
Can you do raku in an electric kiln? Some potters do a modified version, but traditional raku uses a fast-heating kiln, often gas fired, and the ware is pulled out hot. Opening an electric kiln at temperature can damage the elements and brick and is risky, so follow the kiln manufacturer’s guidance.
Can you use cone 6 clay for raku? Some cone 6 bodies may survive raku, but results depend on the specific clay. Look for clays labeled for raku or with grog and thermal shock resistance, and test with small pieces first.
Trying raku
The simplest way to try it is a class or community firing event, where the equipment and experience are provided. You can also practice the shaping and glazing skills in pottery techniques every beginner should learn so your pieces are ready.