What Is a Kiln Firing Schedule?
A kiln firing schedule is a programmed sequence of temperature changes (ramp rates), hold times (soak), and cooling rates that control how clay and glazes mature. Standard bisque schedules ramp at 150°C/hour until 600°C to burn out organics safely (Skutt Kilns manual).
Understanding kiln firing schedules requires mastering three components:
- Ramp rate: Speed of temperature increase (e.g., 200°C/hour for stoneware bisque)
- Soak time: Minutes/hours held at target temperature (e.g., 10 minutes at cone 6 for glaze maturity)
- Cooling cycle: Controlled descent (e.g., 100°C/hour below 700°C to prevent glaze cracking)
Most electric kilns use digital controllers to automate these phases. Manual firing requires cone packs to verify heatwork.
How Do You Read Pyrometric Cones?
Pyrometric cones bend at specific temperatures, measuring heatwork (temperature + time) rather than just heat. Cone 6 bends at 1222°C (Orton Cone Chart, 2024).
| Cone Number | Temperature (°C) | Firing Type | |
| ------------- | ------------------ | ---------------------- | |
| 022 | 600 | Low-fire glaze | |
| 04 | 1060 | Bisque | |
| 6 | 1222 | Mid-range glaze | |
| 10 | 1300 | High-fire stoneware |
Cones are placed in a kiln sitter or witness cone pack. At 30°C below the target, they begin bending, signaling the soak should start. Kiln controllers automate this using thermocouples.
What Temperature Is Cone 6?
Cone 6 reaches 1222°C, the standard for commercial stoneware glazes (Laguna Clay technical docs).
This mid-range temperature:
- Vitrifies stoneware (3-5% absorption)
- Activates most commercial glazes
- Uses 18% less energy than cone 10 firings
How Long Does a Bisque Firing Take?
Bisque firing typically takes 8–12 hours, including a 1-hour soak at 600°C to burn out organics (Paragon Kilns guide).
Variables affecting duration:
- Kiln size: A 23" x 27" kiln adds 2 hours vs. a 18" model
- Clay type: Porcelain requires slower ramps (80°C/hour) than stoneware (150°C/hour)
- Load density: 75% full kilns fire fastest
Proper loading cuts 15% off firing times by improving airflow.
What Is the Difference Between Bisque and Glaze Firing?
Bisque firing prepares porous clay for glazing (Cone 04/1060°C), while glaze firing melts coatings onto the surface (Cone 6–10/1222–1300°C).
| Firing Type | Target Cone | Purpose | Soak Time | |
| ------------- | ------------ | ----------------------- | ----------- | |
| Bisque | 04 | Burn organics | 60 min | |
| Glaze | 6 | Melt glaze | 10–30 min |
Critical difference: Bisque schedules ramp faster (150–200°C/hour) but glaze firings need precise holds to avoid blistering. Programmable kilns handle this best.
Can You Fire Pottery Without a Kiln Controller?
Yes, but manual firing risks ±15°C fluctuations vs. ±3°C with digital controllers (Skutt KM-1227 specs).
Trade-offs:
- Manual: Requires cone packs, constant monitoring, and 20% more test firings
- Digital: Repeats schedules exactly; 80% fewer glaze defects reported by studio surveys
Raku and pit firings skip controllers entirely but limit glaze options.
Bottom Line: Are Kiln Firing Schedules Worth Mastering?
Yes—precise schedules reduce glaze defects by 68% (Ceramic Arts Network).
- Consistency matters: 5°C variations cause gloss/matte glaze differences
- Clay maturity: Underfired bisque absorbs 40% more glaze unevenly
- Energy savings: Optimized schedules cut kiln runtime by 25%
Shop programmable controllers for repeatable results.