What is a standard cone-6 glaze firing schedule?

A common starting schedule for cone-6 glaze firing: 300°F/hr to 1000°F, then 200°F/hr to 1500°F, then 150°F/hr to 2100°F, then 108°F/hr to 2232°F (cone 6) with a 10-minute hold. This schedule takes approximately 8 to 10 hours in a medium-size kiln. Individual schedules should be verified with witness cones at first use and adjusted for specific clay body, glaze, and kiln size.

How slow does a bisque firing need to start?

For standard leather-hard or bone-dry greenware, starting the bisque at 200°F per hour to 250°F is common practice. The critical range is from room temperature to 212°F (100°C) where physical water evaporates. Very thick pieces, handbuilt work with air pockets, or work that is not fully dry before loading require a slower initial ramp, sometimes as slow as 27°F per hour. Work that fires too fast in this range can crack or explode from steam pressure inside the clay walls.

Can I use the same firing schedule for all my clay bodies?

A standard schedule works as a starting point for most commercial stoneware and porcelain bodies, but clay bodies vary in their thermal expansion behavior and organic content. High-grog bodies and heavily grogged clay bodies typically tolerate faster rates than smooth porcelain. Some clay bodies with high sulfur content benefit from a hold or slow rate through the quartz inversion zone around 1063°F (573°C). The manufacturer's firing recommendations for your specific clay body are the best starting point.

What is the quartz inversion point and why does it matter?

Quartz inversion occurs at approximately 1063°F (573°C) when crystalline silica in the clay body undergoes a rapid phase change between alpha and beta quartz. During heating, this expansion is generally not a problem if firing proceeds at a moderate rate. During cooling, the contraction at this point is where most cracking occurs in freshly fired work. Slow cooling through this range (approximately 100°F/hr from 1150°F to 900°F) reduces thermal shock and is recommended for large pieces or work with thick-to-thin transitions.

Why does the firing schedule have a hold at peak temperature?

A hold at peak temperature allows heat to equalize throughout the kiln load before cooling begins. In a fully loaded kiln, the work in the center of the kiln reaches temperature more slowly than work at the kiln walls. A 10 to 20 minute hold at peak gives all the work time to reach the target cone level. It also helps glaze surfaces level and heal pinholes that form during the final stages of glaze melt. For a lightly loaded kiln, a shorter or no hold may be adequate.

Kiln Firing Schedules: Bisque and Cone-6 Starting Points

A firing schedule defines how fast the kiln climbs to temperature, whether there are any holds along the way, and how the kiln cools at the end. Electric kilns with digital controllers program schedules as a series of ramp segments, each with a rate (degrees per hour) and a target temperature. The schedules below are starting points based on manufacturer-published programs and common studio practice.

Two types of firings cover almost all studio work: bisque firing, which converts greenware to fired ceramic, and glaze firing, which matures glazes on bisqued work. They have different schedule requirements.

Bisque firing schedule (cone 04)

Bisque firing takes greenware (clay that has air-dried but not yet been fired) through the transformation to a porous fired ceramic. The critical constraint is the initial heating rate: greenware still contains physical water that must evaporate slowly enough to avoid steam explosions.

Standard slow bisque schedule:

Segment	Rate	Target	Hold
1	200°F/hr	250°F	30 min
2	200°F/hr	1100°F	0 min
3	150°F/hr	1700°F	0 min
4	108°F/hr	1945°F (cone 04)	15 min

Total firing time (including hold): approximately 12 to 15 hours in a fully loaded medium kiln.

Standard medium bisque schedule:

Segment	Rate	Target	Hold
1	250°F/hr	250°F	0 min
2	300°F/hr	1100°F	0 min
3	200°F/hr	1700°F	0 min
4	108°F/hr	1945°F (cone 04)	15 min

Total firing time: approximately 9 to 12 hours in a fully loaded medium kiln.

Source: Based on Skutt Kilns published bisque programs and L&L kiln schedule documentation. Verify with witness cones on first use with any new clay body or kiln.

Row of colorful glazed ceramic mugs showing successful cone-6 glaze results — A glaze firing produces results directly tied to whether the schedule reached and held the target cone level. Underfired glazes sit on the surface and can be scratched off; correctly fired glazes are chemically fused to the clay body. (Photo: anathea, CC BY 2.0 via Flickr)

Why each bisque segment exists

Segment 1 (slow climb to 250°F): Physical water in the clay evaporates in this range. Even thoroughly dried greenware retains moisture in the clay matrix. Firing too fast here causes steam to build inside the clay walls faster than it can escape, resulting in cracks or explosive delamination. Very thick pieces, handbuilt work with air pockets, and work that may be slightly damp need the slowest rate; bone-dry thin work can tolerate the faster medium rate.

Segment 2 (climb to 1100°F): Organic matter in the clay burns out in this range. Carbon from organic materials in the clay body must be fully burned off before the clay body closes up at higher temperatures. If carbon gets trapped, the result is dark spots (carbon coring) in the finished ware. This segment can proceed at a moderate rate once physical water has been fully evacuated.

Segment 3 (climb to 1700°F): The clay body begins converting from plastic clay to ceramic in this range. This segment proceeds at a steady rate.

Segment 4 (final approach at 108°F/hr): The standard Orton final rate matches the rate at which Orton cone temperature equivalencies were established. Firing at this rate through the final 200 to 400°F before the target cone matches how the cone will behave at its published temperature. The 15-minute hold allows the full load to equalize.

A kiln at high temperature glowing orange through its spy holes — A schedule is only as good as the heat it controls: at peak, the chamber glows the even orange of a kiln holding temperature. *jitze via Flickr. CC BY 2.0.*

Cone-6 glaze firing schedule

Glaze firing loads bisqued (previously fired) ware. Because the physical and chemical water has already been driven off in bisque, the glaze schedule can climb more quickly from the start.

Standard cone-6 glaze schedule:

Segment	Rate	Target	Hold
1	300°F/hr	1000°F	0 min
2	200°F/hr	1500°F	0 min
3	150°F/hr	2100°F	0 min
4	108°F/hr	2232°F (cone 6)	10-20 min

Total firing time: approximately 8 to 10 hours in a fully loaded medium kiln.

Fast cone-6 glaze schedule:

Segment	Rate	Target	Hold
1	400°F/hr	1000°F	0 min
2	250°F/hr	1600°F	0 min
3	200°F/hr	2100°F	0 min
4	108°F/hr	2232°F (cone 6)	10 min

Total firing time: approximately 6 to 8 hours. Faster schedules produce different glaze surface qualities in some glaze chemistries; verify with witnesses before running at production volume.

Source: Based on Skutt Kilns and L&L published glaze firing programs. Adjust to your specific glaze and clay body.

Finished glazed ceramic bowl after kiln firing showing rich color glaze surface — A properly fired glaze firing produces a glaze surface that is chemically matured: fused to the bisque body, resistant to scratching, and developed to its intended color and surface character. The hold at peak temperature helps glaze surfaces level and pinholes heal before cooling begins. (Photo: Tobyotter, CC BY 2.0 via Flickr)

Why each glaze segment exists

Segment 1 (fast initial climb): Bisqued ware can tolerate a fast initial rate because no steam pressure can develop. Early climbing through the first 1000°F is the main way to shorten a glaze firing without affecting glaze results.

Segment 2 (moderate climb to 1500°F): Some glaze materials melt and become active in this range. Carbon from organics in underglazes and organic colorants burns off. A moderate rate allows off-gassing to complete before the glaze seals over.

Segment 3 (careful climb to 2100°F): Glazes begin melting and flowing in the 1500°F to 2000°F range. Crawling, pinholes, and cratering problems often start in this zone. A slower rate gives the glaze time to settle, off-gas, and begin leveling before reaching full melt.

Segment 4 and hold: The final approach at 108°F/hr standardizes the rate at which the target cone level is reached. The hold at peak (10 to 20 minutes) gives the full load time to reach temperature and the glaze time to level. For tight kilns with dense loads, longer holds are better. For lightly loaded kilns, shorter holds or no hold may be adequate.

Cooling and quartz inversion

Most digital controllers manage only the heating schedule. Some controllers (including the Skutt KilnMaster and Bartlett Genesis) support controlled cooling segments as part of a ramp-hold program. Controlled cooling matters in two situations:

Quartz inversion (approximately 1063°F / 573°C during cooling): Crystalline silica in the clay body contracts rapidly at this point. Large pieces and work with significant thick-to-thin transitions are vulnerable to thermal shock cracking here. Slow cooling through this range (approximately 100°F/hr from 1150°F to 900°F) reduces stress. For typical functional studio ware (mugs, bowls), the kiln’s natural cooling is usually adequate. For large sculptural pieces or porcelain with dramatic wall thickness changes, controlled cooling through this range is worth adding.

Glaze fit and crazing: Some glazes prone to crazing benefit from a slow controlled cool from peak temperature through the glaze solidification range. This is a glaze chemistry issue rather than a structural one and is specific to particular glaze recipes.

Ceramics workshop with ware boards holding greenware and bisqueware ready for the kiln — Greenware and bisqueware follow different schedules because they have different constraints. Greenware requires the slow initial ramp to prevent steam cracking; bisqueware has already been fired once and tolerates faster initial heating. Keeping greenware and bisqueware separate and firing them on their respective schedules is the foundation of consistent kiln results. (Photo: Mariusz Raniszewski, CC BY-SA 4.0 via Wikimedia Commons)

Programming schedules into the controller

Both the Skutt KilnMaster and the Bartlett Genesis on the L&L e23T offer two modes:

Cone-fire mode: the simplest option. You select the target cone (04 for bisque, 6 for glaze) and a speed (slow, medium, fast). The controller runs its stored factory schedule for that cone and speed. Cone-fire mode is the right starting point for potters learning their kiln’s behavior.

Ramp-hold mode: manual programming. You enter each segment’s ramp rate and target temperature, plus any hold time. The schedules in the tables above can be entered as ramp-hold programs. Ramp-hold mode gives control over every variable in the firing; it is the mode experienced potters use once they have characterized how their kiln and materials respond.

For full details on controller features including cone-fire and ramp-hold modes, see the kiln controller guide. For cone temperature reference including the cone numbering system, see pyrometric cones explained. For individual kiln controller details, see the KM-1027 review and L&L e23T review.