Cone 04 vs cone 6 vs cone 10

Cone 04, cone 6, and cone 10 mark three levels of heat-work, not three fixed temperatures. Fired at 108 F per hour over the last 180 F, self-supporting Orton cones bend near 1945 F (1063 C) for cone 04, 2232 F (1222 C) for cone 6, and 2345 F (1285 C) for cone 10.

Published July 22, 2026 · Source: Orton temperature equivalent chart, published by L&L Kilns

Those three numbers are what most studios organize around: low fire, mid fire, and high fire. Each range brings its own clay bodies, its own glaze chemistry, its own energy bill, and its own rate of wear on electric elements. Choosing between them is mostly a question of what you want the finished pot to do.

One thing to hold onto before any comparison. A cone measures heat-work, meaning temperature and time together. Orton publishes its temperature equivalents against a stated heating rate for the last 180 F of the firing, and the same cone bends lower when you fire slower and higher when you fire faster. Every number below is quoted at 108 F per hour unless another rate is named.

What is the difference between cone 04, cone 6, and cone 10?

About 400 F between the ends of the range. At 108 F per hour, cone 04 bends near 1945 F (1063 C), cone 6 near 2232 F (1222 C), and cone 10 near 2345 F (1285 C). More heat-work means more glass formed inside the clay, so a higher cone gives a denser, less porous, stronger body.

• Cone 04, low fire. About 1945 F (1063 C) at 108 F per hour, 1915 F at 27 F per hour, and 1971 F at 270 F per hour. Earthenware and terra cotta. Bright, stable color. A porous body that relies on glaze rather than vitrification to hold water.
• Cone 6, mid fire. About 2232 F (1222 C) at 108 F per hour, 2165 F at 27 F per hour, and 2269 F at 270 F per hour. Mid-range stoneware and some porcelains. Dense enough for functional ware, and the range most electric studios settle on.
• Cone 10, high fire. About 2345 F (1285 C) at 108 F per hour, 2284 F at 27 F per hour, and 2381 F at 270 F per hour. High-fire stoneware and porcelain. A tight, vitreous body, and the traditional home of reduction glazes.
• Cone 06, for reference. About 1828 F (998 C) at 108 F per hour. A common bisque cone, roughly 400 F below cone 6 and comfortably below where any mid-fire body matures.

The heating-rate columns deserve a second read. Cone 6 spans 2165 to 2269 F depending only on how fast the last stretch runs, a spread of over 100 F. That is why a controller reporting 2232 F is not the same thing as a cone 6 firing, and why a witness cone stays in the load.

Which clay bodies suit each cone?

Match the body to the cone the maker specifies, not the other way round. Earthenware matures at cone 04 and will bloat or slump well before cone 6. Mid-range stoneware and porcelain are formulated for cone 5 to 6. High-fire bodies need cone 9 to 10 to vitrify and stay chalky and porous if fired short.

Earthenware at cone 04 stays porous, which is why traditional low-fire ware depends on the glaze to hold water. That porosity is a property, not a defect. It is what lets terra cotta breathe in a planter and what makes low-fire slips and majolica behave the way they do.

Cone 6 became the default for electric studios because it approaches the density of high fire without the cost or the element wear. A cone 6 stoneware fired properly usually lands under about 2 percent absorption, which is fine for functional pots. Cone 10 goes further, and a well fired cone 10 porcelain approaches zero absorption with the translucency to show for it.

Whatever the range, the clay supplier data sheet is the authority. It lists a firing range, a shrinkage figure, and an absorption figure, and it will tell you whether a body is happy at both cone 5 and cone 6. Test tiles, weighed dry and again after a boil, are the honest way to check vitrification in your own kiln.

How do glazes behave at each cone?

Color gets harder as the cone gets higher. Low fire keeps the bright reds, oranges, and yellows that burn out above cone 04. Mid fire trades some of that palette for durability. High fire narrows the palette further but opens up celadons, shinos, and the reduction vocabulary that needs both the temperature and the atmosphere.

The melt behaves differently too. A cone 04 glaze is a soft, low-melting glass that gets its fluidity from boron, lead-free frits, and alkalis. A cone 10 glaze can rely on feldspar and whiting alone, which is why classic high-fire recipes look so short. Cone 6 sits in between and generally leans on frits or another boron source to bring the melt down.

Cone 6 glazes also gain the most from a cooling program. Matte and satin surfaces at mid fire depend on crystals that grow roughly between 1900 and 1450 F, so a controlled cool can change the surface without any change to the recipe. The kiln cooling schedules guide covers how to write that segment.

Glaze thickness behaves differently across the three ranges too. A low-fire glaze applied thick tends to craze or crawl rather than run, because the melt is stiff. A cone 10 glaze applied thick will happily run onto the shelf, because the melt is fluid and gravity has an extra 400 F of softness to work with. Mid fire sits in between, which is one reason cone 6 studios can get away with slightly generous dipping.

How long does a firing take at each cone?

Longer as the cone goes up, though the pace you choose matters more than the peak. A medium cone 04 glaze firing often reaches temperature in six to eight hours. A medium cone 6 firing commonly runs eight to eleven hours to peak, and a cone 10 firing longer again, before any cooling program is added.

Cooling is the part people forget when planning a day. Any electric kiln takes most of a day to come back below 200 F, and a well insulated kiln loaded with heavy shelves takes longer. A cone 10 firing that reaches peak at midnight is not a kiln you open at breakfast. Build the cool down into the plan rather than treating it as dead time at the end.

The bisque adds another firing to every cycle whatever range you fire to, usually cone 06 or cone 04, and usually slower than the glaze firing because organics need the time. That is the same for low, mid, and high fire, so it does not tip the comparison one way or the other. It does mean a working week has two firings in it, not one.

Does firing to cone 10 cost more?

Yes, in three ways: energy, time, and elements. A cone 10 firing runs about 113 F hotter than cone 6 at the same heating rate, and it takes longer to get there, so the kiln draws power for more hours. The element bill is the part most people underestimate.

Skutt states the mechanism plainly: element life is governed by how fast the aluminum in the alloy oxidizes, and the hotter the element runs, the faster that happens. Time at high temperature compounds it, which is why a long slow cool at cone 6 also costs element life. Firing a cone 10 rated kiln to cone 6 is gentler on elements than pushing a cone 6 rated kiln to its ceiling, because the more powerful kiln reaches temperature sooner and spends less time up there.

The practical version: low fire is the cheapest per firing and the kindest to a kiln, mid fire is the compromise most studios make, and high fire costs the most in power, in element replacements, and in hours. Gas kilns change that arithmetic, since fuel and atmosphere replace elements as the limiting cost. The electric vs gas kiln firing guide compares the two.

Which cone should I choose?

Start from the work, then check the kiln. If you want bright low-fire color or sculptural terra cotta, cone 04 is the range. If you want functional pots from an electric kiln with sensible running costs, cone 6. If you want reduction surfaces or the tightest porcelain, and you have the kiln for it, cone 10.

1. Check what your kiln is rated for. A cone 6 rated kiln fired to cone 6 every week will chew through elements.
2. Check what your clay supplier stocks in that range, and what glazes you can buy or mix for it.
3. Check what electricity costs where you are and how often you plan to fire.
4. Fire a test load with witness cones before committing a body of work to a new range.

Whichever range you pick, the manufacturer manual sets the ceiling and the witness cone settles any argument about what actually happened in the load. Set the cone and the speed in the firing schedule builder to see the segments each range needs, then read the cones and adjust from there.