Two firings, two jobs
Most pottery is fired twice. Each firing has a different purpose, and confusing the two is a common source of beginner mistakes.
Bisque firing
The first firing turns fragile, bone-dry clay into a harder, still-porous state called bisque. This firing is generally taken to a lower temperature than the glaze firing. The porosity is intentional: it lets the piece absorb glaze in the next step.
Glaze firing
The second firing melts the glaze and brings the clay body to maturity, the point at which it becomes dense and durable. This firing usually reaches a higher temperature than the bisque. After it cools, the piece is finished.
- Bisque firing
- Hardens clay; leaves it porous so it can take glaze. Lower temperature.
- Glaze firing
- Melts the glaze and matures the clay body. Higher temperature.
What cones measure
Potters talk about firing to a "cone" rather than only a temperature. Pyrometric cones are small shaped pieces that bend when a specific combination of heat and time has been reached. Because they respond to heat work over time, not just a peak number on a dial, they are a more reliable guide to whether a glaze and clay have actually matured. Clay and glaze products list the cone they are designed for.
Fire slowly at the start
Any moisture trapped in a thick or recently made piece turns to steam as the kiln heats. Heating too quickly can cause that steam to crack or even break the work. A slower early stage gives moisture time to escape, which matters most for thicker walls.
Buying or sharing a kiln in Canada
Many beginners do not own a kiln at first. Community and college studios across Canada often fire student work for a fee, which avoids a large upfront purchase while you learn.
- Electrical supply: most home electric kilns require a dedicated circuit sized to the kiln's rating. Have the installation checked by a licensed electrician.
- Ventilation: firing releases fumes, so kilns need adequate ventilation following the manufacturer's guidance.
- Space and clearance: kilns get very hot on the outside and need clearance from walls and anything flammable.
Follow the manual
Specific firing schedules, clearances, and safety requirements vary by model. The kiln's own manual and your local electrical and fire codes are the authoritative sources. These notes are general background, not installation instructions.
For a general overview of kiln types and history, the public reference on the kiln gives helpful context alongside the practical notes above.