The most critical phase of creating pottery is the firing. The least creative, it is the most technical and the point at which you discover if all your efforts have been successful.
If you have had questions about how hot a kiln gets or what temperature ranges kilns operate in, keep reading.
Here, we will attempt to explain what you need to know about kiln temperature ranges and how they are used.
How Hot Does a Kiln Get?
There are rare exceptions, but the majority of pottery kilns will reach temperatures in the 2000 to 2400 degrees Fahrenheit (1100-1300 C.) range. This is because the majority of clays mature in this range, as do most glazes.
There are some high-fire porcelain clays that require slightly higher temperatures, but these are considered specialty works. Because of this, many kilns intended for general use by home potters or small commercial shops will only reach temperatures of 2000-2300 degrees F. (1100-1250 C.).
Kiln Temperature Range
Clays, glazes, and the pottery kilns used to mature or fire them are generally broken down into three categories based on temperature ranges. This makes it easy to match the mediums you can use with the kiln you have available.
Low-fire kilns are those that operate in the 1740 to 2020 °F range. This is hot enough for low-fire clays like those used to make earthenware and the low-temp glazes that are used to finish and seal them. A wood-fired pottery kiln and all other ceramic kilns fall in this category.
This would be a kiln capable of a firing temperature range of Cone 015 to Cone 1.
If you want to move up into creating mid-range stoneware and similar wares, then a mid-range kiln that operates between 2120 and 2270 °F.
This is equivalent to Cone 2 to Cone 7.
Kilns in this category can be subdivided into two more categories. Those intended for firing high-fire stoneware and those that can be used for creating porcelain ware.
High fire stoneware Kiln
High-fire stoneware is stronger and more durable than standard stoneware and must be fired hotter. A high-fire kiln suitable for high-fire stoneware will need to reach temps of 2300 and 2340 degrees Fahrenheit which is equivalent to Cone 8 and Cone 12 firing.
A kiln suitable for firing porcelain will need to be capable of firing at Cone 10 to Cone 13. In terms of temperature range, this equates to between 2380 and 2460 degrees Fahrenheit.
The one exception in this category is kilns intended for making fine kaolin porcelain and china. These specialty kilns can reach a temperature of 3270 degrees Fahrenheit. There are few kiln manufacturers who build these kilns for the commercial market.
Cases of Different Temperatures
Clays and glazes can vary greatly, and firing them too cool or hot will yield unsatisfactory results.
If fired at too high, temperature glazes can burn off or run off. Clays can deform and, in extreme cases, even melt.
If fired at too low a temperature, your pottery may come out rough and porous and fail to solidify properly. Your Glazes will also be negatively affected, with them failing to cure and harden being the most common result.
To help assure that you get the best possible results when firing ceramic materials, in this section, we will break down the best temperature ranges for each clay body and type of glaze within each temperature category.
Over the course of human history, there has undoubtedly been more low-fire pottery produced than any other type. From mans earliest pit firings, low fire has been a mainstay and remains very popular today.
clay body types
Low fire is generally reserved for earthenware, with terra cotta being the most popular clay body type among home potters. Other forms you may see are recreations of Native American pottery and Early European pottery made from wild clay.
Low fire clays normally have a high percentage of iron, silica, and other naturally occurring compounds and achieve their reach optimum hardness between 1745℉ (950℃) and 2012℉ (1100℃), which equates to Cone 015 to Cone to 1.
Advantages and disadvantages
Low fire clays have the advantage of being very easily worked and resisting sagging and shrinkage. They do, however, generally remain slightly porous even when fully hardened and are not as sturdy as clays that are fired at higher temperatures.
Low-fire clays can vary greatly in color depending on the mineral content of clays used. However, they do allow for the use of a wide variety of low-fire glazes and organic-based very low-fire glazes that will burn away at higher temperatures. You can also find many metallics, iridescent, and enamel glazes in this firing range.
While all of these can be used to create stunning effects, some do tend to leave a dull finish or a clearly separate glaze layer.
Low fire kiln manufacturers
There are few companies producing kilns dedicated to low-fire glazes and clays. Instead, they produce kilns designed for mid-range glazes and clays or high-fire stoneware. These can, of course, be used at the lower temperatures needed for low-fire clay and glazes.
The use of mid-range glazes, clays, and kilns became popular with the advent of gas and electric kilns. Mid-range is normally defined as operating between 2120 and 2270 °F or Cone 2 to Cone 7.
Though high-fire stoneware clay works overtook mid-range clay offerings for a period of time, mid-range has again become the most popular form of ceramics as artisans have become more aware of the power and fuel use required for their kilns.
It should be noted that stoneware comes in two different forms; mid-range and high fire. In this section, we will be discussing the nature of mid-range stoneware only.
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Clay body types
Stoneware is the predominant form of mid-range clays used around the world. It gets its name from the dense stone-like nature of finished works.
Stoneware is a fairly plastic clay body, but the grey to white clay is often mixed with other types of clays to modify its working characteristics or the nature of finished creations.
A mid-range kiln should fire in a 2124℉ and 2264℉ (1162-1240℃) temperature range. This is Cone 2 to Cone 7 temperatures.
At these temperature settings, there is a vast array of finishes that can be achieved in glazed pottery. Being the most popular temperature range, there is an endless supply of glazes and finishes available.
Advantages and disadvantages
Unglazed Mid-range stoneware is grey to brown in color and slightly porous and soft. Still, it is harder and more durable than earthenware. Luckily, there are a number of underglazes and finishes available in the mid-fire range that can be used to seal the clay.
Many traditional finishing methods such as salt glazing and ash glaze fall in this temperature range, making it wonderful for people who are interested in producing Rustic Americana reproductions.
Mid-range Kiln manufacturers
Virtually every major kiln producer has several models that fall into this category. Just a few of our top picks would include:
- Skutt Kilnmaster Series
- Skutt Kilnmaster Touchscreen Series
- Amaco Excel Kiln with Select Fire
- Paragon Iguana Digital Front-Loading Kilns
High-fire is any clay, glaze, or kiln that reaches beyond 2270 °F (1244 °C) or fires above Cone 7. This would include high-fire glazes, stoneware, porcelain, and the kiln temperatures that it takes to work with them.
Clay bodies that mature at these kiln temperatures are much more durable and finer-grained than those fired at lower temperatures. They are, for the most part, universally food-safe, and many pieces reach the level of fine art.
Clay body Types
Stoneware dominates the high-fire clay body types. These are very fine-grained and rock hard. High-fire stoneware clay is very similar to mid-range clay but generally has more refractory elements and fewer fluxing agents in its makeup.
Also, like mid-range stoneware, other clays are often added to a high-fire stoneware clay body. The difference is that, in most cases, ball clays are added to mid-range stoneware, and fire clays are most often used in high-fire stoneware to raise the maturation temperature.
High fire glazes for stoneware are more limited in color selection due to the effects of the oxidation and reduction atmospheres that higher temperatures produce. Still, there are a few coloring oxides that can provide bright finishes.
A body-glaze layer will often form in high fire stoneware, and the raw clay, while vitrified, will remain a dull grey to buff color.
The average firing temperature for high-fire stoneware is 2381℉ (1305℃), which is approximately Cone 10. However, anywhere in the Cone 8 to Cone 12 range (2305℉ to 2336℉, 1263℃ to 1326℃) may be used depending on the specific clay, glazes used, and the effect the artisan is hoping to achieve.
Advantages and disadvantages
The biggest advantage that high-fire stoneware brings to the table is that it is completely vitrified (turned to glass) and completely non-absorbant. This makes it ideal for tableware and mugs.
Being dense and durable makes high-fire stoneware very popular in both home and industrial applications; unfortunately, it also makes it rather heavy when compared to some other forms of ceramics.
As noted earlier, there are also fewer finishing options available in the high-fire glaze category but what can be used is just as tough as the clay bodies it is applied to.
When discussing kilns, the only real disadvantage is the added fuel or power consumption needed to reach and maintain the high kiln temperatures needed to fire these clays and glazes.
High-Fire Kiln Producers
Our choices in kilns for high-fire stoneware are much like those we picked for mid-range firing. The best on the market is still the best, and you just have to go to a more powerful model.
While the Iguana can reach Cone 10 temperatures, the Dragon and Super Dragon are built of heavier materials and should provide a much longer service life for your investment.
Porcelain is created using kaolin clays. Often referred to simply as white clay, kaolin clays require higher temperatures than other clay types.
Kaolin is the purest form of clay known, they were named for a hill in China where they were first mined.
Clay body Types
Though kaolin clays can be fired and are most translucent when the clay body is made of pure clay, it is often mixed with other clays to improve its workability and lower the firing temperature required to harden it fully.
Porcelain clay bodies are known for their extreme smoothness and harness after being fired. However, they take a great deal of care in how they are cooked as they are subject to warping.
Pure kaolin fires at an extremely high temperature of 3272℉ (1800℃). This is the top of the range at Cone 14.
Very little Kaolin clay is actually worked pure, though; most of what is used will need to be fired between 2381℉ and 2455℉ (1305℃ and 1346℃). For those using pyrometric cones or cone settings on their kiln, this is from Cone 10 to Cone 13.
Advantages and disadvantages
Lacking any alkaline earth, iron, or other alkalies in its makeup, porcelain fires to a translucent, light grey or buff color and in its purest form, a sterling white. It is also very sturdy and hard beyond any other type of ceramic.
Its purity also causes it to form a body glaze layer when fired that is easily distinguishable from other glazes that are plied to it. In terms of overglazes, the options for porcelain are very limited, and most of what is available are pale in nature and not very vibrant.
The majority of kilns on the market peak at the very low end of the temperature range required for firing porcelain clays. However, few of us will ever have the need to fire pure kaolin clays.
Any of the kilns that we have recommended that will reach a Cone 10 firing will suffice for firing most of the blended clays on the market.
Frequently Asked Questions
Can you use your oven as a kiln?
No, households and even the best commercial ovens are not capable of reaching the temperatures needed for firing clay and turning it into ceramics. In fact, most of the materials used to construct a standard home oven would melt in a kiln.
What is the maximum temperature of a kiln?
The highest temperature that a kiln can reach will vary depending on the type and design of the kiln. Wood-fired kilns are limited to about 2,845 degrees Fahrenheit (1,563 degrees Celsius), and most cannot even approach this temperature.
Most commercially available gas and electric kilns will top out in the 2100 to 2300 ℉ range. However, there are those that can reach temperatures as high as 3272℉ (1800℃). These are kilns specifically designed for firing pure kaolin clays and are generally only found in industrial settings.
How hot does a kiln make a room?
Even the most up-to-date kilns can make a room uncomfortably hot. A kiln room should always be ventilated not only to help prevent overheating but to remove any toxic fumes or disperse heavy metals that might be produced during firing sessions.
A kiln should never be operated in an unventilated space.
Can pottery explode in the kiln?
Yes, pottery can explode in a kiln, and it happens frequently enough that it is not earth-shatteringly unusual when it does.
There are many things that can contribute to pottery exploding, including air-pockets in the clay and walls that are too thick, but the root cause is moisture. When the clay reaches 212 degrees F, any moisture left in the clay will quickly turn to steam and, if trapped, cause the clay to explode.
What temperature is it safe to open a kiln?
Various kiln manufacturers give different guidelines as to when it is safe to open their kilns, but generally, between 125 and 250F is considered safe.
The more the kiln has cooled, the safer it will be for both you personally and your pottery. The thermal shock of cool air entering a kiln and striking hot pottery can cause it to shatter. Patience is a virtue.
How hot does the average kiln get?
In general terms, most of the best kiln for home use options or small shop use will be capable of reaching temperatures in the 2000 to 2300 degrees Fahrenheit range.
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I’m Jessica and I’m obsessed with kilns. I’ve been doing pottery from when I was a little girl and I created TypesOfKilns to help people find the right kiln for their needs.