Bisque Firing vs Glaze Firing: Pottery Temperatures Explained
Most studio pottery is fired twice. The first firing is the bisque. The second is the glaze firing. They are not the same temperature, and they are not doing the same job.
If you have ever wondered what cone 06 vs cone 6 means, or why you cannot skip the first fire "to save time," this is the map.
Bisque firing vs glaze firing in one look
Bisque firing turns bone-dry clay into ceramic. The pot becomes hard enough to handle and porous enough for glaze to grip. It is usually lower than the clay's final maturity.
Glaze firing melts glaze into glass and, on most stoneware paths, takes the clay the rest of the way to mature, vitrified ware. It is usually hotter than bisque for the same clay body.
Typical community-studio pattern:
- Bisque: cone 08 to cone 04 (often cone 06)
- Glaze, mid-fire stoneware: cone 5 to cone 6
- Glaze, high-fire stoneware or porcelain: cone 9 to cone 10
Your clay bag and glaze bucket beat any blog table. Match clay, glaze, and kiln schedule to each other. Reading Cones and Matching Clay to Glaze is the habit.
What a cone actually is
A pyrometric cone measures heat-work, not just a thermometer peak. Time at temperature matters. Two kilns that both "hit 2200°F" can still fire differently.
Cone numbers look backwards at first:
- Cone 06 is cooler than cone 6
- Cone 04 is hotter than cone 06
- Cone 10 is hotter than cone 6
Learn the object in What Is a Pyrometric Cone?, then practice with Set Witness Cones in a Cone Pack. Controller readouts are useful. Bent witness cones are the report card.
Typical temperatures (approximate)
Numbers vary by cone chart and hold time. Treat these as orientation, not a program to type in blindly.
- Cone 06: about 1828°F / 998°C
- Cone 04: about 1945°F / 1063°C
- Cone 6: about 2232°F / 1222°C
- Cone 10: about 2345°F / 1285°C
Earthenware often bisques and glazes lower (think cone 06 glaze on terracotta-style bodies). Stoneware and porcelain usually want a hotter glaze fire. Types of Pottery Clay and Stoneware vs Porcelain help you pick a path.
Why fire twice?
You can single-fire some work. Beginners usually should not.
Two firings give you:
- A chance to handle and sand bisque without destroying a leather-hard form
- Porous ware that accepts dipping, brushing, and pouring
- A moment to inspect cracks before you invest glaze and a hotter load
- Safer, more predictable glaze application
Bisque is the dress rehearsal. Glaze fire is opening night.
If a pot is still wet, skip both. Steam explodes work. Dry to bone dry first: How Long Does Pottery Take to Dry?.
What happens in a bisque firing
Bone-dry clay still holds chemically bound water and burnout material. The kiln has to go slowly enough that this leaves without blowing the walls apart.
Good bisque habits:
- Candle (a long, low preheat) on thick or doubtful loads: What Is Candling?
- Load so air can move: The Rules of Bisque Loading
- Do not stack pots that will warp into each other
- Leave lids on or slightly propped per studio rule, consistently
Practice the plan on paper first: Plan a Bisque Load and Program a Bisque Firing Schedule.
After unloading, inspect. Cracks, S-cracks, and exploded bits are information. Inspect Bisqueware for Defects. Then glaze using Pottery Glazing for Beginners.
What happens in a glaze firing
Glaze melts, flows, and (if well fitted) bonds to the clay. Clay itself continues to mature. This load needs clearance because glaze is liquid at peak.
Good glaze-fire habits:
- Wax and wipe feet so pots do not glue to shelves
- Leave space for runny glazes
- Match the cone to both clay and glaze
- Use stilts only when the studio says that clay and firing allow it
If the glaze crawls or looks starved, that is often application or cleanliness, not the cone number alone. See Why Is My Pottery Glaze Crawling? and How Many Coats of Glaze Should You Actually Use?.
Common questions
Can I glaze greenware? Some people do, with compatible clay, glaze, and a careful single-fire schedule. In a class studio, follow the house process. Two-step is the default for a reason.
Is bisque always cooler than glaze? For mid-fire and high-fire stoneware, yes, typically. Some earthenware glazes fire near bisque temperatures. Always read the labels.
Why did my pot survive bisque and crack in glaze? Thickness, thermal shock, poor glaze fit (crazing or shivering), or a schedule that climbed or cooled too fast. Cracks have a separate field guide: Why Pottery Cracks.
When can I open the kiln? When the studio says so, usually well after the controller hits room-ish temperatures. Early peeking is how people thermal-shock good work.
What to write down after every firing
Kiln notes pay rent forever:
- Clay body and cone rating
- Bisque cone and date
- Glaze names, application, and cone
- Shelf position if results vary in that kiln
- What you would repeat
Claybook is built to keep those firing notes next to the pot, not on a dusty post-it. Learn cones, loading, and schedules in short lessons. Then stop guessing which fire did what.
Two firings feel slow until you lose a load to steam or a glued-down mug. Then the extra kiln run looks like the cheapest insurance in the studio.