If you're staring at an older electric kiln controller—something like a Skutt KilnMaster, an early L&L DynaTrol, or a basic 3-6 segment digital controller—and feeling lost, you're not alone. These workhorses are reliable, but programming them isn't exactly intuitive.
Unlike modern touchscreen controllers with pre-programmed firing schedules, older controllers require you to manually input every single segment: ramp rate, target temperature, and hold time. Miss one number or misunderstand what a segment does, and you're looking at underfired bisque, melted glaze running onto your kiln shelf, pinholes, or temperature overshoots that waste electricity and stress your elements.
The good news? Once you understand what each segment actually does during the firing process, programming becomes straightforward. This guide breaks down the three most common firing schedules potters need, explains what's happening in each segment, and shows you how to troubleshoot when things go wrong.
Why Older Controllers Are Different
Modern kiln controllers often have one-button firing programs: press "Cone 6 Medium" and walk away. Older controllers don't work that way.
You're building the firing schedule from scratch. Each segment needs three pieces of information:
- Ramp rate (how fast temperature climbs, usually in degrees per hour)
- Target temperature (where this segment ends)
- Hold time (how long to maintain that temperature before moving to the next segment)
Get any of these wrong and the firing fails. Enter "04" when you meant "1940°F"? Your kiln stops way too early. Program a ramp that's too fast through water smoking? Your greenware explodes.
Common older controller models:
- Skutt KilnMaster
- L&L DynaTrol (pre-2010 models)
- Bartlett 3-key and 6-key controllers
- Generic digital controllers with 3-6 programmable segments
If your controller has a small LCD screen and requires you to scroll through segments manually, this guide is for you.
The Three Essential Firing Schedules
We're covering the schedules almost every potter needs:
- Slow Bisque to Cone 04 (≈1940°F / 1060°C)
- Medium Glaze to Cone 6 (≈2232°F / 1222°C)
- Medium Glaze to Cone 06 (≈1828°F / 998°C)
For each schedule, we'll break down every segment, explain what's happening inside your kiln, and give you troubleshooting tips for common problems.
Firing Schedule 1: Slow Bisque to Cone 04
Best for: Greenware of any thickness, studios that want to avoid cracking or blowouts
Target temperature: 1940°F (1060°C)
Total firing time: 10-14 hours depending on kiln size and load density
Why Bisque Firing Is Delicate
Bisque firing transforms fragile greenware into durable ceramic. But greenware still contains moisture, organic materials, and undergoes chemical changes during heating. Rush any of these stages and you get cracks, explosions, or black coring inside your clay.
Older controllers are actually ideal for bisque firing because you have complete control over each heating stage. Modern "fast bisque" programs often move too quickly for thick work or dense loads.
Segment-by-Segment Breakdown
| Segment | Ramp Rate | Target Temp | Hold Time | Purpose |
|---|---|---|---|---|
| 1 | 100°F/hr | 200°F | 30 min | Water smoking |
| 2 | 150°F/hr | 600°F | 0 min | Carbon burnout |
| 3 | 200°F/hr | 1000°F | 0 min | Through quartz inversion |
| 4 | 300°F/hr | 1830°F | 0 min | Sintering begins |
| 5 | 150°F/hr | 1940°F | 10 min | Final maturity |
Segment 1: Water Smoking (Room Temp → 200°F)
What's happening: Clay contains mechanical water—moisture that's not chemically bonded but trapped in the clay structure. When heated, this water turns to steam. If steam can't escape fast enough, it creates pressure that literally explodes your pieces.
Ramp: 100°F per hour (very slow)
This gives water time to migrate to the surface and evaporate gradually. Thicker pieces need slower ramps; thin pieces can handle slightly faster.
Hold: 30 minutes at 200°F
This hold ensures even heat distribution throughout your kiln load. The center pieces catch up to the outer pieces, and all water is fully driven off.
Troubleshooting: If you see steam condensation on your kiln lid during this stage, or if pieces are popping or cracking, slow this ramp to 75°F/hr and extend the hold to 45 minutes.
Segment 2: Carbon & Organics Burnout (200°F → 600°F)
What's happening: Organic materials in clay (plant matter, carbon, sulfur compounds) burn off as gases. This is why bisque kilns smell during this phase.
Ramp: 150°F per hour
Fast enough to be efficient, slow enough to let gases escape without pressure buildup.
Troubleshooting: Black coring (dark spots inside broken clay) means organics didn't fully burn out. Slow this segment to 100°F/hr, especially if you're using clay with high organic content or if you've added materials like paper clay.
Segment 3: Quartz Inversion (600°F → 1000°F)
What's happening: At around 1063°F, quartz crystals in clay undergo a structural change called inversion. The crystals suddenly expand, creating stress in the clay body.
Ramp: 200°F per hour
Moderate speed lets the entire piece experience quartz inversion together, minimizing stress differentials.
Troubleshooting: S-cracks (cracks in a roughly S-shape) or dunting (cracking with a "ping" sound) often trace back to this segment being too fast. Reduce to 150°F/hr if you're seeing these issues.
Segment 4: Sintering Begins (1000°F → 1830°F)
What's happening: Clay particles begin fusing together. The clay body gains strength and starts becoming permanently ceramic.
Ramp: 300°F per hour
You can move faster here because the dangerous chemical changes are complete. The clay is stable and just needs heat.
Troubleshooting: If your kiln takes too long overall, this is the segment you can safely speed up. Try 350-400°F/hr if your firing is exceeding 14 hours.
Segment 5: Final Heatwork (1830°F → Cone 04 / 1940°F)
What's happening: Clay reaches full bisque maturity. It's now porous enough to absorb glaze but strong enough to handle easily.
Ramp: 150°F per hour (controlled)
Slowing down at the end prevents overshooting your target temperature.
Hold: 10 minutes
This brief hold ensures even heatwork throughout the kiln—top, middle, and bottom all reach the same maturity.
Troubleshooting: Uneven bisque (some pieces over-fired, some under-fired) usually means inadequate soaking time at peak temperature. Extend this hold to 15-20 minutes.
Common Bisque Problems and Fixes
Problem: Stalled firing (kiln stops climbing around 1200°F)
- Likely cause: Segment programmed incorrectly or kiln thinks it reached target
- Fix: Verify each target temperature is entered correctly in Fahrenheit, not cone number
Problem: Cracking during firing
- Likely cause: Too-fast ramp through water smoking or quartz inversion
- Fix: Slow Segments 1 and 3, extend hold at 200°F
Problem: Black coring inside thick pieces
- Likely cause: Organics didn't burn out completely
- Fix: Slow Segment 2 to 100°F/hr
Firing Schedule 2: Medium Glaze to Cone 6
Best for: Stoneware glazes, functional ware, high-fire work
Target temperature: 2232°F (1222°C)
Total firing time: 8-10 hours
Why Cone 6 Is Tricky on Older Controllers
Cone 6 is a long firing. Older kilns with worn elements struggle to reach peak temperature, and some controllers shut off automatically if the firing exceeds their programmed time limit (often 12-14 hours). You need a schedule that reaches temperature efficiently without rushing glaze development.
Segment-by-Segment Breakdown
| Segment | Ramp Rate | Target Temp | Hold Time | Purpose |
|---|---|---|---|---|
| 1 | 200°F/hr | 250°F | 0 min | Preheat |
| 2 | 400°F/hr | 1100°F | 0 min | Efficient climb |
| 3 | 300°F/hr | 2000°F | 0 min | Glaze softening |
| 4 | 150°F/hr | 2232°F | 10 min | Peak maturity |
| 5 | -100°F/hr | 1900°F | 0 min | Controlled cool (optional) |
Segment 1: Preheat (Room Temp → 250°F)
What's happening: Bisque ware can absorb moisture from the air, especially in humid climates. This segment drives off any moisture in your bisque or kiln furniture.
Ramp: 200°F per hour
Fast enough to be efficient, slow enough to prevent glaze crawling from moisture.
Troubleshooting: Glaze crawling (bare spots where glaze pulled away from clay) can result from moisture. If you live in a humid area, slow this to 150°F/hr.
Segment 2: Mid-Range Heat-Up (250°F → 1100°F)
What's happening: Not much. This is dead zone where glaze components haven't started melting yet. You're just moving efficiently toward active temperature ranges.
Ramp: 400°F per hour (fast)
No reason to go slowly here. Save time for segments that matter.
Segment 3: Glaze Softening Zone (1100°F → 2000°F)
What's happening: Glazes begin softening. Fluxes activate, glass-formers start melting, and colorants begin developing. Clay body starts vitrifying (becoming glass-like and non-porous).
Ramp: 300°F per hour
Moderate pace allows proper glaze development without rushing chemical reactions.
Troubleshooting: Dry, under-melted glazes sometimes indicate your kiln is struggling to maintain this ramp rate. If your actual firing shows the kiln slowing down significantly here, your elements may need replacement. Check our kiln elements section for replacements.
Segment 4: Peak Cone 6 Maturity (2000°F → 2232°F)
What's happening: Glazes fully melt, mature, and develop their final surface quality. Clay body reaches full vitrification.
Ramp: 150°F per hour (controlled)
Slowing down prevents temperature overshoot, which can cause glazes to run off pieces or change color.
Hold: 10 minutes
This soak time is crucial. It allows glaze chemistry to complete and helps heal surface defects like pinholes and orange peel texture.
Troubleshooting: Pinholes or rough glaze surfaces often improve with a longer hold. Try 15-20 minutes. If problems persist, your issue might be glaze application thickness or chemistry, not firing schedule.
Segment 5: Controlled Cool (Optional)
What's happening: Rapid cooling can trap gases in glaze, creating cloudiness or tiny bubbles. Slow cooling lets gases escape and improves glaze clarity.
Ramp: -100°F per hour (controlled cooling) to 1900°F
This means you're actively controlling cooling speed rather than just turning the kiln off.
Note: Many older controllers can't program negative ramp rates (controlled cooling). If yours can't, simply skip this segment. Your glazes will still work fine.
Common Cone 6 Problems and Fixes
Problem: Overfiring past Cone 6
- Likely cause: Kiln climbs too fast at the end or wrong target temperature entered
- Fix: Verify target is 2232°F, slow Segment 4 ramp rate
Problem: Kiln shuts off before reaching temperature
- Likely cause: Firing time exceeds controller's maximum time limit
- Fix: Speed up Segment 2 to 450°F/hr to reduce overall firing time
Problem: Glaze pinholes or orange peel texture
- Likely cause: Insufficient hold at peak temperature
- Fix: Extend Segment 4 hold to 20 minutes
Firing Schedule 3: Medium Glaze to Cone 06
Best for: Commercial low-fire glazes, bright colors, earthenware
Target temperature: 1828°F (998°C)
Total firing time: 6-8 hours
Why Cone 06 Is Different
Low-fire glazes mature quickly and are sensitive to temperature. Too fast and colors don't develop properly. Too slow and you waste time and electricity. The short temperature range (from glaze melting to full maturity) means precision matters.
Segment-by-Segment Breakdown
| Segment | Ramp Rate | Target Temp | Hold Time | Purpose |
|---|---|---|---|---|
| 1 | 300°F/hr | 250°F | 0 min | Initial ramp |
| 2 | 400°F/hr | 1100°F | 0 min | Efficient mid-range |
| 3 | 250°F/hr | 1750°F | 0 min | Glaze melt zone |
| 4 | 150°F/hr | 1828°F | 5 min | Final maturity |
Segment 1: Initial Ramp (Room Temp → 250°F)
What's happening: Moisture removal from bisque ware and kiln furniture.
Ramp: 300°F per hour
Faster than bisque because there's no greenware to worry about. Bisque can handle rapid heating.
Segment 2: Efficient Mid-Range (250°F → 1100°F)
What's happening: Dead zone—nothing important happening with glaze chemistry yet.
Ramp: 400°F per hour (fast)
Get through this quickly to save time and electricity.
Segment 3: Glaze Melt Zone (1100°F → 1750°F)
What's happening: Color development begins. Glazes start softening. This is where low-fire glaze magic happens.
Ramp: 250°F per hour
Moderate pace ensures even color development and proper glaze maturation.
Troubleshooting: Dull or uneven colors? Try slowing this segment to 200°F/hr. Some commercial low-fire glazes need slower development for full color saturation.
Segment 4: Final Cone 06 Maturity (1750°F → 1828°F)
What's happening: Glazes reach full melt without overshooting into Cone 05 or 04 territory (which can change colors dramatically).
Ramp: 150°F per hour (controlled)
Slow approach prevents overshoot. Low-fire glazes are sensitive—even 20°F too hot can ruin them.
Hold: 5 minutes
Brief hold ensures even heatwork. Commercial clear glazes especially benefit from this—it improves clarity and gloss.
Troubleshooting: If clear glazes look cloudy or colored glazes look wrong, verify your actual peak temperature with witness cones. Older controllers sometimes drift and display incorrect temperatures.
Common Cone 06 Problems and Fixes
Problem: Uneven color development
- Likely cause: Firing too fast through Segment 3
- Fix: Slow to 200°F/hr through glaze melt zone
Problem: Clear glazes staying cloudy
- Likely cause: Insufficient hold at peak temperature
- Fix: Extend Segment 4 hold to 10 minutes
Problem: Temperature overshoots
- Likely cause: Final ramp too fast
- Fix: Reduce Segment 4 ramp to 100°F/hr
Programming Tips for Older Controllers
Entering Segments Correctly
Each controller interface is slightly different, but the process is similar:
- Enter Program Mode (usually a button labeled "PROG" or "MENU")
- Select segment number (Seg 1, Seg 2, etc.)
- Enter ramp rate (degrees per hour)
- Enter target temperature (in Fahrenheit or Celsius, depending on your controller)
- Enter hold time (in minutes)
- Repeat for each segment
- Save/Exit when complete
Critical: Always enter actual temperatures (like 1940°F), not cone numbers (like 04). Controllers don't understand cone numbers—they need actual temperatures.
Common Programming Mistakes
Mistake 1: Entering cone numbers instead of temperatures
- Wrong: Entering "06" when you mean Cone 06
- Right: Entering "1828" for Cone 06
Mistake 2: Forgetting to program all segments
- If you program Segments 1-3 but forget Segment 4, your kiln will stop at whatever temperature Segment 3 ends at
Mistake 3: Not accounting for your kiln's age
- Older kilns with worn elements may need slower ramp rates in later segments because they can't maintain fast heating at high temperatures
Maintaining Firing Records
Keep a logbook of every firing:
- Date
- Kiln load (heavy, medium, light)
- Firing schedule used
- Actual firing time
- Results (any problems, how pieces turned out)
Over time, you'll notice patterns. Maybe your kiln always needs 15 extra minutes at peak temperature. Maybe heavy loads require slower ramps. This data helps you customize schedules for your specific equipment.
Troubleshooting Checklist
Before you blame your firing schedule:
Check your elements: Worn elements can't maintain programmed ramp rates, especially at high temperatures. If your kiln is slowing down significantly during the firing, elements are usually the culprit.
Verify your witness cones: Don't trust your controller's temperature display completely. Place witness cones in every firing to verify actual temperature.
Check voltage: Low voltage to your kiln (extension cords, undersized breakers, shared circuits) prevents proper heating.
Assess your load: An extremely dense, heavy load requires more time and energy than a light load. Adjust ramp rates accordingly.
Test individual segments: If a firing fails, test each segment individually to find where the problem occurs. Program just Segments 1-2, fire, and check. Then program 1-3, and so on.
When to Upgrade Your Controller
Older controllers work fine, but consider upgrading if:
- Your controller frequently loses programs
- The display is failing or unreadable
- You can't program enough segments for complex schedules
- You want features like controlled cooling or automatic cone fire modes
Modern controllers like the Bartlett Genesis or Orton AutoFire offer pre-programmed schedules, better interfaces, and diagnostic features that older controllers lack.
Final Thoughts
Older electric kiln controllers require more hands-on programming than modern systems, but this actually gives you better control once you understand what each segment does. Instead of relying on a generic "Cone 6 Medium" program that might not suit your specific kiln, clay, or glazes, you're building custom schedules that work for your situation.
The key is understanding the "why" behind each segment:
- Water smoking prevents explosions
- Carbon burnout prevents black coring
- Quartz inversion requires careful ramping
- Peak temperature holds improve glaze quality
Once you grasp these principles, programming becomes intuitive. You're not just entering numbers—you're controlling a complex chemical process with precision.
At Sheffield Pottery, we carry everything you need for successful firings: kiln elements, kiln furniture, witness cones, and glazes formulated for consistent results. Whether you're troubleshooting an older controller or upgrading to new equipment, we're here to help you fire with confidence.
Frequently Asked Questions
Can I use these schedules on any kiln?
These schedules work for most electric kilns, but you may need to adjust ramp rates based on your kiln's size, age, and element condition. Larger kilns heat more slowly. Older kilns with worn elements can't maintain fast ramp rates at high temperatures.
Why does my controller show different cone numbers than I programmed?
You programmed actual temperatures (like 1940°F), which is correct. Some controllers display a "cone equivalent" based on that temperature, which might not match exactly. Trust the temperature you programmed, not the cone display.
How do I know if my elements need replacing?
If your kiln takes significantly longer to reach temperature than it used to, or if it can't reach peak temperature at all, elements are likely worn. Most elements last 100-200 firings depending on use.
Can I skip holds at peak temperature?
You can, but holds improve results. They ensure even heatwork throughout the kiln and help heal surface defects in glazes. A 10-minute hold uses minimal extra electricity but significantly improves quality.
What if my controller only has 3 segments?
Combine segments strategically. For bisque: (1) Water smoking to 200°F with hold, (2) Steady climb to 1830°F, (3) Final to 1940°F with hold. For glaze: (1) Fast to 1100°F, (2) Moderate to 2000°F, (3) Controlled to peak with hold.
Should I upgrade to a modern controller?
If your current controller works and you understand how to program it, there's no urgent need to upgrade. But modern controllers offer convenience, pre-programmed schedules, better diagnostics, and features like controlled cooling that older models lack. It's a quality-of-life improvement, not a necessity.