Raku Firing Explained: Process, Glazes and Safety

Raku is the most dramatic firing in pottery. You heat glazed pots in a small kiln, lift them out glowing, and bury them in smoking material. The results can be metallic lusters, crackled whites and deep carbon blacks that no other method gives you.

It is also physical and risky. This guide explains how it works and what to respect before you try it.

How raku differs from regular firing

In a normal firing, you load a kiln, close it and let it cool slowly for a day or two. Raku turns that upside down:

• The kiln is small and heats quickly, often in under an hour.
• Pots are removed while the glaze is molten.
• They go straight into combustible material such as newspaper or sawdust.
• The container is covered, so the burning material uses up the oxygen and pulls it from the glaze and clay. That is reduction.

The sudden change in temperature is a severe shock, so raku needs a clay body that can survive it. Raku clay usually contains grog (pre-fired clay particles) to resist thermal shock.

The process

1. Make and bisque fire your pots in a conventional kiln.
2. Glaze with raku glazes, which are designed for low-temperature firing. Leave the foot unglazed.
3. Load the raku kiln and heat until the glaze melts, usually a bit above 900°C (1650°F). Many raku glazes mature near the cone 06 range, so see our cone chart.
4. Remove pots with long tongs while the glaze is glossy.
5. Place them in a metal can lined with combustibles and cover with a lid.
6. Wait a short time while the material smokes.
7. Quench in water or air-cool, depending on the effect you want.
8. Scrub off the carbon and ash to reveal the surface.

What happens to the surface

• Unglazed clay turns black from carbon.
• Crackle glazes show a web of black lines where carbon entered the cracks.
• Metallic glazes develop copper, bronze or iridescent colors in reduction.

Results are partly out of your control. That is the appeal, and the frustration.

Safety is not optional

Raku involves fire, burning smoke and glowing pots. Treat it seriously.

• Work outdoors with good ventilation and a clear space.
• Wear cotton or wool clothing, never synthetic fabrics that melt.
• Use heat-resistant gloves, a face shield and closed shoes.
• Wear a respirator suitable for smoke when handling combustibles and removing ash.
• Keep a water source and a fire extinguisher nearby.
• Never fire alone. Have a second person who knows the plan.

Raku is best learned at a workshop with an experienced instructor before you build a setup at home.

Raku pots are not for food

Raku glazes are usually low-fire and not intended for food contact, and the crackle can trap liquids. Treat raku as decorative ware. Our guide on food safety explains why.

Prepare your pots

Good raku starts well before the kiln. Thick joins and trapped air cause pots to crack. Dry thoroughly, bisque fire carefully and use a suitable clay body. See prepare pieces for a raku firing.

Record every firing

Raku effects are difficult to repeat unless you write down what happened. Note the glaze, how long you waited, the combustible material and the quench. Claybook lets you log these details with photos on each piece.