Glaze firing is the second trip through the kiln. The pots are already bisque, now coated in raw glaze, and the kiln takes them up to the temperature where that glaze melts, flows into a smooth layer and bonds to the clay. As the kiln cools, the melt hardens into glass. For stoneware and porcelain, the glaze firing is also when the clay itself finishes maturing, so it becomes dense and close to waterproof.
This guide covers what happens in a glaze firing, how to pick the cone, how a typical schedule is built, how to load glazed work and what to do when glazes come out wrong. The first firing has its own guide: see bisque firing for candling, bisque cones and packing a bisque load. This page is research-based: we compared kiln and clay maker guides, Orton's cone chart and published ceramic references, and we did not run test firings ourselves.
Bisque firing vs glaze firing
Most kiln firing in a home studio is one of these two jobs. They look similar on a controller but have different goals.
| Bisque firing | Glaze firing | |
|---|---|---|
| Goes in as | Bone dry greenware | Glazed bisqueware |
| Typical cone | 06 to 04 | 06 to 05 (low fire), 5 to 6 (mid fire), 10 (high fire) |
| Main risk | Steam and trapped water cracking pots | Glaze running, sticking or forming defects |
| Can pieces touch? | Yes | No |
| Shelves | Kiln wash optional | Kiln wash strongly advised |
| Comes out | Porous, ready to glaze | Finished, glassy surface |
What happens during a glaze firing
A glaze is mostly silica (the glass former), alumina (which stiffens the melt so it stays on the pot) and fluxes (which lower the melting point), plus colorants. Our clay and glazes hub explains those ingredients. In the kiln, the firing moves through a few stages:
- Drying off. Water from the glaze coat and any moisture the bisque picked up leaves at low temperature. This is why glazed work should dry fully before loading; Laguna's glaze firing guide says to let glazed work dry overnight.
- Burnout. Binders, gums and any organic matter in the glaze burn away. Gases from the clay pass up through the raw glaze coat.
- Quartz change. Around 1,063°F (573°C) the quartz in clay and glaze changes form and the ware expands slightly. Steady heating through this point avoids stress.
- Melting. As the kiln nears the target cone, the glaze softens, bubbles as gases escape, then smooths into a continuous layer.
- Maturing and cooling. The kiln finishes at the cone, sometimes with a short hold, then cools. As it cools, the glaze sets into glass and, in some glazes, crystals grow and give matte or speckled surfaces.
What cone should I glaze fire to?
Fire to the cone written on your glaze, and make sure your clay is rated for that same cone. The glaze cone is where it melts properly; the clay cone is where the body matures without slumping. Those two must agree. Most home potters work in one of three ranges:
| Range | Typical glaze cone | Temperature (108°F/hr finish) | Clay it suits |
|---|---|---|---|
| Low fire | 06 to 05 | 1,828°F to 1,888°F (998°C to 1,031°C) | Earthenware, terracotta, low-fire white bodies |
| Mid fire | 5 to 6 | 2,167°F to 2,232°F (1,186°C to 1,222°C) | Mid-fire stoneware and porcelain |
| High fire | 10 | 2,345°F (1,285°C) | High-fire stoneware and porcelain |
Temperatures are from Orton's chart for self-supporting cones; our pottery cone chart lists every cone at two heating rates. Laguna's own cone 5/6 glaze firing guide prints slightly lower targets (2,163°F for cone 5 and 2,228°F for cone 6). The few degrees between the two sources matter less than confirming the result with witness cones on the shelf.
Low-fire potters often bisque a little hotter than they glaze. Laguna's glaze guide suggests a cone 05 to 04 bisque before a cone 06 glaze firing, so gases leave during the bisque rather than under the glaze. Mayco does the same with its ready-made bisque: soft fired to cone 04/03 and meant for cone 06/05 glazes. Stoneware is the opposite: bisqued low (around cone 04) and glaze fired much higher.
If your kiln is rated only to cone 6, check every glaze label before you buy. A cone 10 glaze will not melt properly at cone 6. Cone 6 and cone 10 are the two main stoneware ranges, and few glazes cross between them.
A typical glaze firing schedule
Most digital controllers have built-in glaze programs: you pick the cone and a speed, and the controller does the rest. If you write your own, it usually follows the shape Laguna publishes for cone 5 and 6:
| Segment | Rate | To | Purpose |
|---|---|---|---|
| 1 | 50°F/hr (see note) | 200°F | Dry off any moisture |
| 2 | 100°F/hr | 800°F | Burn out organics and gases |
| 3 | 150°F/hr | 1,300°F | Pass quartz inversion, drive off bound water |
| 4 | 200°F/hr or faster | Cone 5 or 6 | Melt and mature the glaze |
| Hold | None | 5 to 10 minutes at top | Even out heat through ware and shelves |
Laguna's guide is not consistent on the first segment: the schedule lists 50°F per hour, while the text says 100°F per hour. Both are gentle starts; follow your kiln manual or clay supplier if they give a figure. Laguna adds that going slowly near the end or holding at peak is "always best".
A whole glaze firing usually takes most of a day to heat and as long again to cool. The heatwork matters more than the clock: a long hold or a slow finish adds heat, and can push a cone 6 firing toward cone 7. Our guide to the cone 6 firing schedule goes into programs and timings in detail.
Drop and hold, and slow cooling
Some potters change the end of the firing to improve the glaze surface. A drop-and-hold (or drop-and-soak) schedule reaches the top, then lets the kiln fall by 100°F to 200°F and holds there. Digitalfire explains that the cooler, stiffer melt can heal pinholes and blisters. Its PLC6DS example climbs at 350°F per hour to 2,100°F, slows to 108°F per hour to 2,200°F, holds 10 minutes, falls to 2,100°F and holds 30 minutes. Digitalfire also notes that 2,200°F, not the controller's 2,232°F, was what bent its cone 6 correctly in that kiln, which is why witness cones matter. Slow cooling programs, used for matte and crystal effects, work on the same idea.
How to load a glaze kiln
Loading glazed ware is slower and fussier than loading bisque, because anything glaze touches at peak temperature fuses to it. The full routine is in our guide to how to load a kiln; these are the glaze-specific rules.
- Keep glazed pieces apart. L&L's loading guide says glazed ware needs at least 1/4 in between pieces. Melted glaze will weld pots together.
- Clean the foot. Wax the base before glazing or sponge off every trace of glaze from the foot and the lower 1/4 in or so of the wall. Glaze runs down as it melts.
- Use kiln-washed shelves. Wash goes on the top surface only; our kiln wash page covers how and how often.
- Protect shelves from runny glazes. Set pieces with fluid glazes on a "cookie" (a disc of bisque or a ready-made drip tray) so drips land there instead of on the shelf.
- Raise the bottom shelf. L&L says to put it on 1/2 in posts rather than directly on the kiln floor, and to keep shelves at least 1 in from the thermocouple.
- Place witness cones. Skutt suggests self-supporting cones about 2 in from the wall and 2 in from the thermocouple tip, where you can see them through a peephole. Read them after the firing to see how much heatwork the ware really got.
Stilts or dry feet?
Stilts hold a glazed base off the shelf so the whole piece can be glazed. They are mainly a low-fire tool: earthenware stays porous and firm at cone 06. Stoneware and porcelain soften as they mature, so they can sag or pick up marks on stilt points at cone 6 and up. Most mid and high-fire potters leave the foot bare and fire it flat on the shelf. Our guide to kiln stilts covers types and cone ratings.
Cooling and unloading
Let the kiln cool on its own with the lid closed. Opening early can crack pots and shelves and can craze glazes. Makers give different finish lines. Laguna's cone 5/6 guide says not to open the kiln until it is below 400°F, to keep it sealed and switch off any vent while it cools, and to cool slowly around 428°F, where cristobalite in the clay contracts. Skutt's KilnMaster manual is more cautious: leave peepholes plugged and the lid closed until the ware is cool enough to unload barehanded, about 130°F, and do not unload above 125°F. Follow your own kiln's manual, and wear gloves; glazed edges can be sharp.
What kind of glaze kiln you need
Any electric pottery kiln rated for your glaze cone can be a glaze kiln; there is no separate type. Most hobby kilns are rated either to cone 6, about 2,250°F (1,232°C), or to cone 10, about 2,350°F (1,288°C). A cone 10 kiln fires cone 6 glazes easily and wears its elements more slowly at that temperature. A small 120V kiln can glaze fire to cone 6, but most stop there. Check the maximum on your kiln's serial plate before you plan a glaze range.
Common glaze firing problems
Most glaze faults trace back to application, the clay, or the firing. These are the ones home potters meet most:
- Running. Glaze too thick, fired too hot or held too long. Thin the coat, check the cone and use cookies.
- Crawling. Glaze pulls back into beads, leaving bare clay. Usually dusty or greasy bisque or a coat applied too thick. See glaze crawling.
- Crazing. A web of fine cracks in the glaze, caused by a glaze that shrinks more than the clay on cooling. See glaze crazing.
- Pinholes and blisters. Gas bubbles that burst and do not heal. A hotter bisque, a slower finish or a drop-and-hold usually helps.
- Underfired glaze. Rough, dry or cloudy where it should be glossy. Check witness cones and element condition.
- Shivering. Glaze flaking off edges, the reverse of crazing: the glaze is under too much compression for the clay.
Many faults can be fixed by refiring: add glaze to bare or thin spots and fire again to the same cone. Crazing and shivering usually need a different glaze or clay rather than another firing.
Safety notes
Glaze firings release fumes from binders, colorants and fluxes, so run a kiln vent or keep the kiln in a well-ventilated space as your kiln maker directs. The kiln jacket gets hot enough to burn; keep the clearance in your manual (Skutt asks for at least 18 in) and keep flammables away. Have a licensed electrician install or check the kiln circuit. Read the maker's SDS for any glaze you mix from dry materials, and wear a NIOSH-approved respirator when handling dry glaze powders. No glaze is food safe on your pots just because the label says so: results depend on the clay, application and firing to the stated cone.
What you need
A glaze firing needs a kiln rated for your cone, kiln-washed shelves, posts and witness cones for that cone. Our kiln shelves and furniture guide compares shelf kits, posts and kiln wash, and our guide to the best kilns for home pottery covers kilns that handle both bisque and glaze firings.
Sources: Orton Ceramic Foundation temperature equivalents chart for self-supporting cones; Laguna Clay basic glaze firing guide for cone 5 and 6 (schedule, hold, cooling) and glaze usage guide (low-fire bisque and glaze cones); Mayco Earthenware Bisque and Stoneware Bisque pages; L&L Kilns knowledgebase on loading a kiln; Skutt KilnMaster operating manual (witness cone placement, unloading temperature, clearance); Digitalfire glossary on drop-and-soak firing and the PLC6DS schedule; The Pottery People and The Pottery Wheel glaze firing articles (topic coverage). Specs checked October 2026.