What is a low fire glaze?
A low fire glaze is a glass coating designed to melt and smooth out at the bottom of the pottery firing range, usually cone 06 to 04. To melt that early, it leans on strong fluxes. Lead did that job in the past; today commercial low fire glazes are lead free and use boron, mostly supplied through frits (pre-melted glass), according to Digitalfire's reference on low temperature glazes.
The payoff is color. Reds, oranges, bright yellows and pinks that burn out or turn muddy at cone 6 stay crisp at cone 05, which is why classroom and hobby glazes live here. The trade-off is the clay underneath: a low fire body never vitrifies, so the glaze does most of the sealing. Our low fire clay guide covers the bodies themselves.
This page is research-based. We compared maker pages, color charts and brochures from AMACO, Mayco and Spectrum plus Orton's cone data in October 2026; we did not fire these glazes ourselves.
Low fire glaze temperatures: cone 06, 05 and 04
Cones measure heat work (time plus temperature), so the same cone bends at a lower temperature in a slow firing. The figures below are Orton's values at a 108°F (60°C) per hour final climb, the column most kiln controllers use.
| Cone | Temperature (Orton, 108°F/hr) | Typical low fire use |
|---|---|---|
| 06 | 1,828°F (998°C) | Many commercial glazes (often labeled 06/05); some bisque firings |
| 05 | 1,888°F (1,031°C) | The standard target for AMACO LG and Teacher's Palette |
| 04 | 1,945°F (1,063°C) | Common bisque cone; top of many low fire glaze ranges |
| 03 to 01 | 1,987°F to 2,046°F (1,086°C to 1,119°C) | Upper earthenware; few jar glazes are rated here |
Maker brochures sometimes print a single range instead. Mayco's 2025 Elements low fire brochure, for example, says "cone 06-05 / 1830°F-1915°F". Both are right for their heating rate; see the full pottery cone chart for slow and fast columns.
Cone 05 glazes: the low fire standard
If a jar says "low fire," it usually means cone 05, give or take a cone. AMACO's LG gloss glazes fire "to a smooth, glossy finish at a witness Cone 05", and its Teacher's Palette line is a cone 05 gloss for use over cone 04 bisque. Mayco shows its low fire chips at cone 06 on white earthenware and tells you to "fire to shelf cone 06/05." Spectrum rates its 700, 800 and 900 series at cone 06/04 and its 150 metallics at cone 05.
The common pattern for low fire work is a hotter bisque (cone 04) and a cooler glaze firing (cone 06 or 05). The hotter bisque burns out more organic matter before the glaze goes on, which helps reduce pinholes. Our bisque firing guide explains how to pick the bisque cone, and the glaze firing guide covers the second firing itself.
Cone 04 vs cone 4: one zero changes everything
Cone 04 is low fire, while cone 4 is the bottom of mid-range, about 180°F hotter. The leading zero flips the scale, and our cone chart explains the numbering in full.
That matters when you shop for cone 4 glazes. Very few jars are rated for cone 4 alone. Most mid-range glazes are labeled cone 4 to 6 or cone 5 to 6; Spectrum, for instance, files its 1100, 1430 and 1500 lines under "Cone 4/6" on its site. If your kiln tops out around cone 4, a glaze rated "cone 4/6" may still melt, but it is at the cool end of its range, so test first. A low fire glaze, by contrast, will usually be overfired at cone 4.
Low fire vs mid fire glaze
| Point | Low fire (cone 06 to 04) | Mid fire (cone 4 to 6) |
|---|---|---|
| Color | Brightest reds, oranges and yellows | Softer palette; more reactive, breaking surfaces |
| Clay body | Earthenware and low fire white clay, porous after firing | Stoneware and porcelain that vitrify into a dense body |
| Durability | Softer glass; chips and scratches more easily | Harder glass on a stronger body |
| Kiln | Works in small 120V kilns and older kilns | Needs a kiln rated for cone 6 or higher |
| Results | Very predictable; looks close to the chip | More variation between kilns and clays |
Digitalfire sums up the durability point: low fire glazes are less durable than well-made medium temperature glazes, even though they can be very glossy. For a mug you use daily, many potters choose a cone 6 stoneware; for tiles, sculpture, ornaments and classroom work, low fire is often the easier route.
Low fire glaze brands and lines
AMACO low fire glazes
AMACO's low fire glazes center on three lines. Teacher's Palette is a 24-color, intermixable cone 05 gloss for classrooms. LG Low Fire Gloss is the main studio line, with LG-10 Clear Transparent as the clear AMACO names for covering Velvet and LUG underglazes on food surfaces (check LG-10 on Amazon). LM is the smaller matte companion. AMACO also advises: "Always slow fire lead free glazes for best results." Our AMACO glazes review covers every line.
Mayco
Mayco has the widest low fire choice: Stroke & Coat for brushed color (rated cone 06 to 10 on its product pages), Foundations for base colors, and Elements and Jungle Gems for effect glazes on decorative pieces. Mayco's Elements brochure calls for three to four coats on bisque, or no more than two coats on wet or leatherhard clay. See our Mayco glazes review for line-by-line labels.
Spectrum
Spectrum sells a deep low fire range: 700 Opaque Gloss, 800 Semi-Transparent, 900 Low Stone, 250 Satin, 200 Rhinestone, 150 Metallic and crackle glazes. Spectrum's older product guide warns not to combine 900 series glazes with 700 series glazes on the same piece because of expansion mismatch. Our Spectrum glazes review covers the lines and labels.
Can low fire glaze go on stoneware?
It can, and many school studios do exactly this to save kiln time, but the result behaves like a decorative piece. When stoneware is fired only to cone 05, it does not vitrify. It stays porous, and the glaze was designed for a different clay expansion, so crazing is common, either straight out of the kiln or months later. Crazed, porous ware can soak up water and is a poor choice for food.
The other route is to fire stoneware to its full cone first, then apply a low fire glaze and refire at cone 05 or 06. The body is then dense and strong, but the glaze may not bond as well to a vitrified, non-absorbent surface, so it usually needs to go on warm or with a brushing medium and fit is still a test question. For more on clay ranges, see our clay and glazes hub.
Firing low fire glazes at cone 6
Some low fire glazes are made to stretch. Mayco publishes cone 6 chips for many low fire colors and has a page on using them at mid-range. Its notes: many Stroke & Coat colors work, but reds, oranges, yellows, blues and greens may darken, and "lighter colors such as tan, purple and pink will fade." Elements "will be quite fluid and move during the firing process," and Jungle Gems crystals move more and act as a blending agent.
A glaze with no cone 6 rating from its maker is a different story. Expect it to run, thin out, blister or lose color. Only try it on a test tile set in a catch dish or on a waste slab, never straight on a shelf.
How to apply low fire glaze
- Bisque your ware to the cone your clay maker suggests (often cone 04 for low fire clay) and wipe it with a damp sponge.
- Wax the foot and any surface that will touch the shelf.
- Stir or shake the jar, then pour some onto a palette rather than dipping your brush into the jar.
- Brush the number of coats the label calls for, letting each dry. Opaque low fire gloss usually needs two to three coats; semi-transparent glazes go on thinner (Spectrum suggests about two brush coats).
- Keep glaze about 1/4 in (6 mm) above the foot, then fire to the cone on the label with witness cones on the shelf.
Our how to glaze pottery guide covers dipping, pouring and fixing thick spots in full.
Food safety and durability
Low fire glazes can carry a dinnerware-safe label, but the label describes the glaze under the maker's conditions, not your pot. Mayco notes that certain glazes "may not be recommended for dinnerware produced from low fire earthenware clay bodies," because cracks and crevices plus porous clay let water in. Crackle glazes are never dinnerware safe, and any glaze that crazes on your clay loses its seal.
Never assume a low fire pot is food safe. Fire to the exact cone on the label, use a clay the glaze fits, cover underglaze with a clear the maker names, and have finished ware tested by a lab if you plan to sell or gift dinnerware.
Common mistakes
- Reading cone 04 as cone 4 (or 06 as 6) and badly overfiring a whole load.
- Putting a low fire glaze on a cone 6 clay, firing at cone 05, and using the piece as a mug.
- Mixing glaze families from one maker that the maker says not to combine, such as Spectrum 700 with 900.
- Glaze-firing on a bisque that was fired cooler than the glaze, which can trap gases and cause pinholes.
- Fast-firing lead-free glazes when the maker advises a slow firing.
Safety notes
Dry glaze and dried drips contain silica. Wet-wipe your table and floor instead of sweeping, and wear a NIOSH-approved respirator if you mix dry glaze or sand dried glaze. Read the maker's Safety Data Sheet for each jar, especially metallic and caution-labeled colors. Fire in a kiln that is vented and spaced from walls as its manual says; the outside gets hot even at cone 05.
What you need
A low fire studio needs little more than a kiln that reliably reaches cone 04, low fire clay, a clear glaze and a few jar colors. Our best kilns for home pottery guide compares small kilns that cover low fire work.
Sources: Orton Ceramic Foundation cone temperature chart (as used on our cone chart page); Digitalfire glossary "Low Temperature Glaze"; AMACO LG Low Fire Gloss line text (via The Ceramic Shop LG-10 listing) and AMACO Teacher's Palette and LG line pages; Mayco "Low-Fire Glazes at Mid-Range" page, Mayco "Dinnerware & Food Safety" page and Mayco 2025 Elements low fire brochure; Spectrum Glazes 700/800/150 and 900 color charts, 2026 low fire price list and Spectrum Product Guide (2009 edition); competitor coverage reviewed: Digitalfire, Crafty Chica, The Pottery Wheel. Research-based, not hands-on. Specs checked October 2026.