Bisque Firing Schedule for Greenware, Done Right (2026)
A bisque firing schedule takes bone-dry greenware through a controlled ramp to cone 06 (1828°F / 999°C), driving off residual water and burning out organics before glaze firing. Get the ramp rate wrong through the first 1,000°F and you crack pots that took weeks to build.
TL;DR
- A safe bisque firing schedule ramps 60°F/hr to 1,000°F, then speeds up to cone 06 (1828°F) with a 15-20 minute hold.
- The quartz inversion point at 1063°F (573°C) is where most greenware cracks from a fast ramp — slow down through it, not after.
- Thick or damp greenware needs a candling step at 150-200°F for several hours before the main ramp starts.
- A programmable digital controller runs the schedule automatically once it's entered — manual kilns require checking and adjusting the dial by hand.
Why this matters
Greenware is unforgiving. Water trapped in the clay body turns to steam if you heat it too fast, and steam expanding inside a wall has nowhere to go but out — through a crack. The same risk shows up again at 1063°F (573°C), when quartz in the clay body undergoes a physical change called quartz inversion and shifts volume slightly.
A bisque firing schedule isn't a suggestion — it's the sequence of ramp rates, hold times, and target temperatures that gets greenware to cone 06 without breaking it. Every electric kiln from an Olympic DM2818HE to a 40-year-old manual box needs one, and the schedule changes based on wall thickness, clay body, and how dry the ware actually is before it goes in.
What you'll need
- A kiln with a digital controller (manual kilns work too, but you'll babysit the dial)
- Bone-dry greenware — no cool-to-the-touch dampness, no visible sheen
- Cone 06 pyrometric cones (self-supporting or in a cone pack) as a visual backup to the controller readout
- Kiln furniture: shelves, posts, and enough clearance between pieces for airflow
- Ware carts for bisqueware and greenware storage so loaded shelves aren't stacked on the studio floor before firing
- A vent or downdraft system running during the low-temperature segments to clear moisture and organic off-gassing
- 8 to 14 hours, depending on load size and kiln capacity
If you're loading a full kiln of mixed wall thicknesses — a thin bowl next to a thick-walled planter — build the schedule around the thickest piece. It's the slowest thing in the load to dry out and the first thing to crack if you rush it.
The steps
1. Confirm the ware is actually bone-dry
Greenware that feels dry to the touch can still hold moisture in the center of thick walls. Press a piece against your cheek — if it feels cool, there's still water in the clay. Firing damp greenware is the single biggest cause of cracked bisque.
Let questionable pieces sit an extra 24 to 48 hours in open air before loading. This costs you a day; a cracked pot costs you the piece.
2. Load the kiln with airflow in mind
Space pieces so no two touch and no piece touches the kiln wall or elements. Stack shelves with at least an inch of clearance above tall pieces for heat to circulate.
Greenware can touch or stack lightly during bisque since there's no glaze to fuse pieces together — this is the one firing where you can load tighter than a glaze firing. Don't get greedy with lids and small forms wedged into every gap; airflow still matters for even drying.
3. Program the candling segment
For greenware with any residual dampness, or any load with thick-walled pieces, add a candling segment: ramp to 150-200°F and hold for 1 to 3 hours with the lid propped or vents open. This isn't optional for thick work — it's the step that lets trapped water escape as vapor instead of steam pressure.
Bone-dry, thin-walled greenware (mugs, plates, thrown bowls under 3/8-inch wall thickness) can often skip candling and start the ramp directly, but when in doubt, candle. The hour or two costs nothing next to a cracked piece.
4. Ramp slowly through the low range and quartz inversion
Set the first climbing segment to 60°F per hour from room temperature (or from the candling hold) up to roughly 1,000-1,100°F. This range covers both the water-smoking zone and the quartz inversion point at 1063°F (573°C), where the clay body's silica content undergoes a volume shift.
A fast ramp through 1063°F is the second most common cause of bisque cracks after firing damp ware. If your load has thick or dense stoneware bodies, drop the rate to 50°F per hour through this window specifically — most digital controllers let you set that as its own segment.
5. Speed up for the climb to cone 06
Once you're past 1,100°F, the clay body has released most of its water and the crystalline structure has stabilized. Increase the ramp rate to 200-300°F per hour for the climb to cone 06 (1828°F / 999°C). This is also the segment where organic material and any remaining carbon burn out — keep the vent running if your kiln has one.
A programmable digital kiln controller runs this entire multi-segment schedule without you touching a dial. On a manual kiln, this is where you switch the low-medium-high switches up and check temperature by eye against a witness cone every 30-45 minutes.
6. Hold at cone 06 and shut down
Hold the top temperature for 15 to 20 minutes once cone 06 bends. This soak evens out temperature across the load — the center of the kiln typically lags the elements by a few degrees, and the hold closes that gap.
After the hold, shut the kiln off and let it cool naturally with the lid and peepholes closed. Don't crack the lid before the kiln reads under 200°F — thermal shock on a hot bisque load causes dunting cracks that show up as fine lines after the piece cools completely.
7. Verify with cones, not just the digital readout
A controller's thermocouple reading and the actual heat-work inside the kiln aren't always identical, especially on an aging kiln or one with elements that have lost some output. Pyrometric cones measure cumulative heat-work, not just peak temperature, and a cone 06 that hasn't fully bent means the firing underfired even if the digital display hit 1828°F.
Run a witness cone pack on a shelf visible through a peephole for every bisque firing until you trust the kiln's calibration completely.
Troubleshooting
- Pieces crack in a straight line through the wall — almost always a ramp that was too fast through quartz inversion (1063°F) or greenware that wasn't fully dry. Slow the early segments and extend the candling hold.
- Bisque comes out underfired (chalky, soft, cone 06 didn't bend) — the controller reached temperature but heat-work was insufficient, often from aging elements. Calibrate the kiln controller against a cone pack and check element resistance.
- Black core or gray centers in thick pieces — carbon didn't fully burn out before the kiln sealed at higher temperatures. Extend the 1,100-1,700°F segment and keep the vent running longer.
- Uneven color across a load — usually a cold spot from element wear or poor loading density. Rotate loading patterns and check that no piece sits directly against an element.
- Bisque firing takes far longer than expected — a heavily loaded kiln, especially one packed with damp greenware, absorbs more heat energy per segment. Budget extra time rather than pushing the ramp rate to compensate.
Tools and resources
- A digital controller capable of multi-segment programs — most current Olympic, Jen-Ken, and Evenheat kilns ship with one
- A witness cone pack (cone 05, 06, and 07) placed where it's visible through a peephole
- Ware carts for bisqueware and greenware storage to keep loaded shelves off the floor between the drying stage and the kiln
- A vent system sized for your kiln's interior volume, running during candling and the early climb
ProKilnSupply sells kilns and controllers from Olympic, Evenheat, Jen-Ken, and Aim with the programmable segments needed to run a bisque firing schedule automatically. Every order from ProKilnSupply ships with manufacturer warranty coverage, and phone or text support is available if you're not sure which segment count or ramp rate fits your specific load.
What to do next
Once the bisque firing schedule is dialed in for your kiln and clay body, the next decision is the glaze firing schedule — a different ramp profile entirely, since glaze firings hold longer at peak temperature and cool more slowly to avoid crazing. If you're working in stoneware, how to fire cone 6 stoneware in an electric kiln covers that next stage.
FAQ
What temperature is a bisque firing schedule fired to?
Most bisque firing schedules target cone 06, which is 1828°F (999°C). Some studios bisque to cone 04 (1945°F) for harder bisque that absorbs glaze more slowly.
How long does a bisque firing take?
A full bisque firing schedule typically runs 8 to 14 hours from candling through the cone 06 hold and shutdown, depending on load size and ramp rate. Cooling to a safe unloading temperature adds several more hours.
Why did my greenware crack during bisque firing?
Cracking during bisque almost always traces back to a fast ramp rate through the quartz inversion point at 1063°F (573°C) or greenware that wasn't fully dry before loading. Slowing the early segments to 50-60°F per hour fixes most cases.
Do I need to candle greenware before bisque firing?
Candling — a low hold at 150-200°F for 1 to 3 hours — is necessary for thick-walled greenware or any piece with residual dampness. Thin, fully bone-dry pieces can often skip it.
Can I stack greenware pieces during bisque firing?
Yes — greenware can touch or nest lightly during bisque since there's no glaze to fuse pieces together, unlike a glaze firing where every piece needs clearance.
What's the difference between a bisque firing schedule and a glaze firing schedule?
A bisque firing schedule ramps to cone 06 with a short hold and no controlled cooling requirement. A glaze firing goes hotter (cone 6 or higher for stoneware), holds longer, and often needs a controlled cool to prevent crazing.
How do I know if my kiln's temperature reading is accurate?
Run a witness cone pack next to the load and compare the bend against what the digital controller reports at shutdown. A mismatch means the controller needs calibration against the thermocouple reading.
Does a manual kiln need a different bisque firing schedule than a digital one?
The temperature targets are identical, but a manual kiln requires switching low-medium-high settings by hand and checking cones visually, while a digital controller runs the full multi-segment ramp automatically.
One last thing
The quartz inversion point at 1063°F (573°C) doesn't care how experienced you are — it cracks first-time greenware and twenty-year veteran's greenware at the same rate if the ramp is too fast. Slow that one segment down before you touch anything else in the schedule, and most bisque cracking problems disappear entirely.