Bisque firing is the first trip through the kiln for a clay piece. It drives out the last water, burns away organic matter and turns fragile greenware into bisque: hard enough to handle and glaze, but still porous so glaze soaks in and sticks. Most home potters bisque fire to cone 04 or cone 06, a bisque firing temperature of roughly 1,828°F to 1,945°F (998°C to 1,063°C).
This guide is research-based. We compared kiln maker manuals, clay maker data and Orton's cone chart; we did not run test firings ourselves. Sources are listed at the end.
Why bisque fire at all?
Raw greenware dissolves in water and breaks if you look at it wrong. A bisque fire makes it permanent and strong enough to dip, pour and brush glaze without cracking or slumping. Because bisque is porous, glaze dries onto the surface fast and evenly, which makes glazing much easier than on raw clay. Some potters single fire (glaze greenware and fire once), but it is less forgiving, and most glaze labels assume bisque.
If you want the basics on the material itself, our guide to greenware explains each stage before the first firing.
You may also see this first firing called a biscuit firing, especially in British books and older references. It is the same thing: Wikipedia's entry on biscuit pottery notes that biscuit and bisque both mean pottery fired without glaze, and that in two-firing work the first firing is the biscuit firing and the second is the glaze (or glost) firing.
Bisque firing temperature: which cone?
Cone 04 is the most common choice for home studios firing stoneware or porcelain. AMACO says its No. 46 Buff Stoneware can be bisque fired to cone 04 for a porous bisque that takes high-fire glazes easily, and Skutt's KilnMaster manual uses cone 04 for its worked firing-speed example. Cone 06 is also widely used, especially for low-fire work.
| Bisque cone | Temperature (108°F/hr finish) | Temperature (270°F/hr finish) | Result |
|---|---|---|---|
| 06 | 1,828°F (998°C) | 1,855°F (1,013°C) | Softer, more porous bisque; glaze goes on thicker |
| 05 | 1,888°F (1,031°C) | 1,911°F (1,044°C) | Middle ground |
| 04 | 1,945°F (1,063°C) | 1,971°F (1,077°C) | Stronger bisque, still absorbent; more complete burnout |
The trade-off is simple. A lower bisque leaves the ware more absorbent, so glaze builds up faster when you dip. A higher bisque burns out more organic material and carbon, which can reduce glaze defects such as pinholes later, but the bisque absorbs a little less. Follow your clay maker's advice first. If you want one number, the usual bisque fire temp is about 1,945°F (1,063°C) for cone 04 or 1,828°F (998°C) for cone 06. Temperatures come from Orton's self-supporting cone chart; the full list is on our pottery cone chart.
Low-fire potters often bisque a little hotter than they glaze (for example bisque at cone 04 and glaze at cone 06), because shrinkage and gassing then happen in the bisque rather than under the glaze. Stoneware potters bisque far below the glaze cone. Always check the bisque note on your clay's data sheet.
Before you load: make sure the ware is bone dry
Water left in clay turns to steam as the kiln heats. If it escapes too fast it cracks ware, and in thick pieces it can blow chunks off. Skutt's manual says exactly that: residual water escaping as vapor too fast can crack the ware or, in extreme cases, cause it to explode, and large, thick-walled pieces are most at risk.
Bone dry clay feels room temperature against your cheek, looks evenly pale and no longer feels cool. Thick bases and solid sculptures take much longer than thin walls. Our guide to bone dry clay covers the tests and how to get there without cracks.
Candling: the gentle start
Candling means holding the kiln at a low temperature, below boiling, so remaining water leaves slowly. Many digital controllers call it "preheat". On a Skutt KilnMaster, when you enter a preheat time the kiln climbs at 60°F (15°C) per hour to 180°F (82°C) and holds there for the time you set, before the main program starts.
How long to candle depends on how dry and how thick your work is. Thin, truly bone dry pots may need little or none. Thick sculptures, heavy bases or pieces made the day before often get an overnight candle. Our guide to candling pottery goes deeper.
A simple check from many studio teachers: once candling is done, hold a small mirror or a piece of glass near the vent or a cracked peephole (with gloves and care). If it fogs, water is still leaving. Do not touch any hot surface while doing this.
A slow bisque schedule
A bisque fire should be slow early on, while water and organic material burn off, then it can pick up speed. If your controller has a "slow bisque" program, use it for most loads. Skutt's manual says its slow speed for cone 04 takes about 12 hours and is recommended for large or thick-walled pieces; medium takes about 7.5 hours and is "fine for most firings"; fast takes about 4 hours and is only for things like lusters and decals, not bisque.
If you write your own schedule, the shape usually looks like this (the exact rates are for you and your kiln manual to set):
- Candle or preheat below 212°F (100°C) until the ware is fully dry.
- Climb slowly through the next few hundred degrees while chemically bound water leaves the clay.
- Keep it moderate through red heat so carbon and organic matter burn out with air flowing. Quartz in the clay also changes form at about 1,063°F (573°C), which is a stress point for thick or uneven pieces.
- Finish at the target cone (06 or 04), usually with no hold or a short one.
- Cool naturally with the lid closed. Do not open it until the kiln is near room temperature.
Run a kiln vent through the whole bisque. Clay gives off water vapor, carbon compounds and sulfur gases as it burns out, and a vent pulls them out of the room while bringing in the air that helps burnout.
How to load a bisque firing
Bisque is the one firing where pieces can touch. L&L's loading guide says greenware in a bisque firing can touch other pieces, while glazed ware needs at least 1/4 in between pieces. That means you can pack a bisque load tightly:
- Nest and stack carefully. Small bowls can sit inside larger ones, and similar cylinders can go rim to rim. Keep weight low: never put a heavy piece on a thin rim.
- Fire lids in place. A lid fired on its pot shrinks with it, which keeps the fit.
- Raise the bottom shelf. L&L says to put the bottom shelf on 1/2 in posts, never directly on the kiln floor.
- Keep clear of the thermocouple. L&L advises keeping shelves at least 1 in above or below thermocouples.
- Use three posts per shelf and stack posts directly above each other. Our kiln shelves and furniture guide explains why.
- Add witness cones. Skutt suggests self-supporting cones about 2 in from the kiln wall and 2 in from the thermocouple tip.
Kiln wash is meant for glaze firings (AMACO describes coating shelves "prior to a glaze firing"), so it is not essential for bisque, though most potters use the same washed shelves for both. You can bisque fire on bare shelves, since unglazed clay does not fuse to them; the wash only matters later, when glaze drips. For a full walk-through, see how to load a kiln.
How long does a bisque firing take?
Expect most of a day. Skutt's cone 04 examples run about 7.5 hours on medium and 12 hours on slow, plus any candling time, and cooling takes many more hours after the elements switch off. A bisque started in the evening with an overnight candle is often ready to unload the following evening or the morning after. Thick work, a full load or an older kiln with tired elements all push the time up.
Common bisque firing mistakes
- Firing damp ware. The top cause of cracked and blown pieces. When in doubt, candle longer.
- Using a fast program. Fast speeds are meant for decals and lusters, not raw clay.
- Bisquing too hot. Going well past cone 04 on stoneware makes the bisque less absorbent, so glaze goes on thin and runs off.
- Bisquing too low. Very soft bisque is fragile and can leave trapped carbon that causes glaze defects later.
- Stacking heavy on light. Ware softens slightly as it fires; heavy pieces can crack or warp thin ones underneath.
- Skipping ventilation. Bisque fumes are the strongest of any firing.
Cracks that appear after the bisque can sometimes be patched before glaze firing; our guide to AMACO Bisque Fix covers one option.
Safety notes
Dry clay dust contains crystalline silica. Clean greenware dust with a damp sponge or HEPA vacuum, never by dry sweeping, and wear a NIOSH-approved respirator when sanding or handling dry materials. The kiln jacket gets hot enough to burn skin during a firing, so keep the clearance your kiln manual requires (Skutt asks for at least 18 in) and keep flammables away. Have a licensed electrician install or check the kiln circuit.
What you need
A bisque load only needs a kiln, shelves, posts and a few witness cones. If you are setting up, our kiln shelves and furniture guide compares shelf kits and posts, and our best kilns for home pottery guide covers the kilns themselves. Once the bisque is done, move on to glazing your pottery.
Sources: Skutt KilnMaster operating manual (preheat rate, cone 04 speed examples, witness cone placement, clearance, moisture warning); L&L Kilns knowledgebase on loading a kiln; AMACO product pages for No. 46 Buff Stoneware (bisque to cone 04) and Kiln Wash; Orton Ceramic Foundation temperature equivalents chart for self-supporting cones; Wikipedia, Biscuit (pottery) (biscuit and bisque terminology). Specs checked October 2026.