Your Guide to Kiln Temperature Ranges for Pottery

Aug 03, 2023

Kiln temperature firing ranges refer to the temperature levels at which pottery is fired in the kiln. The maturity or the level of development of the clay and glazes is determined by these ranges. The level of heat then has an impact on the final design and functionality of the ceramic objects. Firing ranges can be divided into three categories: low-fire, mid-range, and high-fire.

TLDR: Kiln Temperature Firing Ranges

Low-Fire Pottery is fired at the lowest temperatures, ranging from between 1,700°F to 2,100°F Cone 04-06 (900°C to 1,150°C). Because of the lower firing temperatures, the glaze palette is more colorful and bright.

Mid-Range Pottery is fired at intermediate temperatures, typically between 2,100°F and 2,300°F Cone 5-6 (1,150°C to 1,260°C). It is frequently used with stoneware clay bodies, which are less porous and more durable than earthenware clay bodies. Because of its adaptability and consistency, mid-range firing is the choice of many contemporary potters.

High-Fire Pottery ranges from 2,300°F to 2,700°F Cone 9-10 (1,260°C to 1,480°C). This is the firing range for the densest stoneware and porcelain clay bodies used for dishware. High-fire temperatures produce extremely strong and vitrified pottery, that is less porous and optimal for utility items such as dinnerware and cookware. The high temperatures also allow the clay body to fully mature, resulting in a dense and sturdy finished product.

Understanding Pyrometric Cones and Temperature

The Basics of the Pyrometric Cone System

No discussion of firing ranges would be complete without covering the importance of pyrometric cones and the part they play in understanding firing range definitions. The ceramics industry uses the Orton Pyrometric Cone System to detect and monitor kiln firing temperatures. It uses miniature pyrometric cones composed of ceramic materials that bend and flex at certain temperatures.

Before the introduction of the thermocouple and digital controller, the cone system was the only tool potters and kiln operators had to reliably and precisely monitor a kiln's temperature during firing. Modern kilns have digital control systems ensuring that we don't have to rely on the cone system. If you need to know more about what modern ceramic kiln buyers need to know, check out our link to things to consider when purchasing a pottery kiln. Pyrometric cones are small, triangular structures manufactured from a precisely controlled mix of clay, feldspar, and other elements. Each cone is numbered, such as Cone 022, Cone 6, or Cone 10 corresponding with low, medium, and high fire pottery ranges. These numbers indicate the cone's bending temperature in Fahrenheit or Celsius.

The Pyrometric cones are inserted in the kiln before firing to initiate the process. By installing pyrometric cones at various points in the kiln, potters, and operators can monitor even temperature distribution through the kiln. Furthermore, by evaluating the bending of the pyrometric cones, kiln operators can evaluate the kiln's performance and consistency over time.

Refer to the Orton Pyrometric Cone Chart below to get a better understanding of cones and their temperatures:

This is a complete guide to using cones from the Orton Foundation.

orton kiln temperature chart

Low-Fire Pottery

One of the most popular varieties of clays used in pottery and ceramics are earthenware bodies, sometimes called redware, terracotta, buff-white, or low-fire white. Due to its accessibility, adaptability, and usefulness, it has been used for thousands of years. Let's explore the composition, traits, and many uses of earthenware clay bodies, especially how well it performs in low fire temperatures:

Clay Body Impurities in Low-Fire Pottery

Earthenware clay bodies typically contain higher impurity levels, including iron and other minerals. Earthenware's distinctive reddish-brown or orange color, which is accentuated when fired at low temperatures, is caused by these impurities. The clay's fluidity is enhanced by the iron concentration making it simpler to work with for hand-building and wheel-throwing techniques.

Low-Fire Pottery firing Temperatures

Earthenware clay performs well when fired at low temperatures, typically between 1,700°F to 2,100°F (900°C and 1,150°C) or Cone 04-06. Several benefits come from the low firing temperature, including lower energy costs, faster firing times, and accessibility for potters utilizing lower amperage compact kilns.

Uses for Low-Fire Pottery

Functional pottery created from earthenware clay is used to make mugs, bowls, plates, and vases. Because of the low firing temperatures, the clay will retain its porosity and will require glazing to be food safe. Due to the low firing temperature, the glazes used to finish these works remain vivid and vibrant, which enhances their aesthetic appeal.

Earthenware clay is an excellent material for hand-building decorative and sculptural objects because of its fluidity and workability. This is why artists have chosen to mold, sculpt and produce elaborate creations with it for thousands of years. Intricate details can be painted with underglazes or decorated with colorful glazes on low-fire decorative objects like figurines and tiles.

Due to its forgiving qualities, simplicity of usage, and lower cost, earthenware clay is frequently utilized in educational settings and by amateur potters. Because of its lower firing temperatures, beginners can learn the basics of pottery without having to invest in larger, higher-temperature kilns or specialized tools.

If you are a beginner and do want to invest in a kiln, we recommend you read our guide on the best kilns for beginners.

Kiln Options for Low-Fire Pottery

Electric Kilns for Low-Fire Pottery

Electric Kilns are ideal for beginning and intermediate potters working with low-fire earthenware temperatures. They come in a variety of sizes to accommodate various pottery projects. Small kilns for jewelry-making or small ceramic items are common, as are medium-sized kilns for individual artists or small studios. Larger volume kiln options are typically available as higher temperature kilns. It’s important to look for kilns with digital controllers that can handle cone firing schedules. Some popular low-fire ceramic kiln options would be:

seattle pottery supply model 122

(Seattle Pottery Supply Model 122)

Many of these kilns can be run on 120v household power and are perfect for hobby potters.

Low-Fire Kilns for Raku Pottery

There are a variety of low-fire raku kilns ideal for potters interested in raku firing techniques. Raku kilns exist in a variety of sizes, allowing artists to select the one that best suits their needs. Smaller raku kilns are good for beginners, while larger kilns cater to intermediate potters who want to experiment with different raku firing procedures and create larger raku works. These are some of the best options available on the market.

olympic 1823fle

(Olympic 1823 FLE)

Although you can raku in any type of kiln, these models are proven to have safe clearance access for hot ware retrieval.

Mid-Range Pottery

The composition and characteristics of Mid-Range firing clay bodies, usually stoneware, are made up of high-quality clay minerals that are generally combined with additives such as grog (fired clay pieces) or fine-grained silica (sand) to increase their strength and workability. When compared to earthenware clays, these clay types have higher levels of smoothness and purity, resulting in greater durability and less porosity after firing. They are known for their high versatility, which makes them appropriate for a variety of molding processes like wheel-throwing and hand-building.

Mid-Range Pottery Firing Temperatures

Stoneware clay bodies are intended to be fired at moderate temperatures, ranging from Cone 4 to Cone 7 (about 2100°F to 2280°F (1150°C to 1250°C). The clay vitrifies at these mid-fire temperatures, transforming it into a dense, durable, and non-porous material.

Cone 6, which is approximately 2232°F (1220°C), is the most regularly utilized cone number for mid-fire kiln firing. Cone 6 firing offers a balance between good vitrification and reducing kiln element and furniture wear and tear. Because of its versatility and the vast range of glaze possibilities, this temperature is popular among potters and ceramic artists.

Uses for Mid-Fire Pottery

Stoneware clay bodies are extensively utilized for practical pottery, dinnerware, and kitchenware goods due to their increased strength and reduced porosity. Because of their durability, they are appropriate for everyday use as well as exposure to higher temperatures, such as in ovens and microwaves. In addition, stoneware clay is frequently used for ornamental and sculptural outdoor artwork work, giving artists a diverse canvas for their works.

Color Transformations in Firing Mid-Fire Pottery

Stoneware clay bodies experience significant color transformation at mid-fire temperatures. Before firing, the clay may appear natural or may contain various iron-based impurities, resulting in colors of brown, gray, or even red. The iron compounds react with oxygen in the kiln atmosphere during firing, resulting in a drop in color intensity. Subtle speckling or variegation in the final color may result from the reduction process, giving each piece a distinct and natural appearance.

Surface Treatments for Firing Mid-Fire Pottery

A wide range of surface treatments can be obtained at mid-fire temperatures. Stoneware clay bodies provide several surface treatment options, ranging from glossy glazes to matte or semi-matte finishes. Furthermore, mid-fire glazes can exhibit stunning color diversity and depth, boosting the finished piece's overall visual appeal.

Kilns for Mid-Range Pottery

Mid-range pottery, which is fired at stoneware clay body temperatures, necessitates kilns with higher firing temperatures than low-fire earthenware. Kilnfrog.com provides a variety of kiln solutions for mid-range stoneware firing, catering to potters of varying skill levels.

Electric Kilns for Mid-Range Pottery

For novices, small to medium-sized electric kilns with intuitive digital controllers are advised. These kilns are easy to use and provide accurate temperature control. Beginners might start with smaller kilns that are suited for single projects or small quantities of pottery. Intermediate potters would benefit from medium-size electric kilns with modern touchscreen digital interface controllers. These kilns provide greater flexibility in firing schedules and programs. Intermediate to advanced potters should investigate larger capacity kilns to accommodate larger pieces or several projects. More advanced Potters' looking to improve their firing capabilities, might invest in even larger electric kilns with even more advanced control systems including multiple thermal control zones for accurate temperature distribution and intricate firing processes. These are some of our favorite options:

Mid-Range Kiln Options for Raku Pottery

For beginners and intermediate potters experimenting with raku firing procedures, portable and smaller raku kilns are recommended. Raku firing is frequently done outside, and smaller kilns are easier to manage and transport. Here’s a great example of an easy and portable kiln that can be used for Raku and will hit mid-range firing temperatures:

Gas Kilns for Mid-Fire/ High-Fire Pottery

Gas kilns with simple controls are ideal for beginning and intermediate potters working with mid-range stoneware clay bodies. Since gas kilns provide greater firing flexibility, including oxidation and reduction atmospheres. Upper intermediate and advanced Potters' will get consistent and intricate outcomes, if they opt for larger gas kilns with many burners and precision control systems. For complex applications, gas kilns with downdraft or updraft designs can provide improved temperature distribution.

These kilns are fantastic mid-range firing kilns and are gas-powered to get the job done right! Incidentally, these models will also hit high-fire temperatures as well giving you perfect flexibility and financial economy as well.

High-Fire Pottery

The composition and characteristics of clay bodies suitable to high-fire temperatures, typically stoneware and porcelain, have minimal impurities and iron content. When fired at high temperatures, these clay bodies have been carefully formulated to deliver optimal strength, density, and vitrification. They are refined and processed in order eliminate variability and provide predictable performance.

High-Fire Pottery Firing Temperatures

High-fire stoneware clay bodies are created to endure firing temperatures ranging from Cone 8 to Cone 10; 2300°F to 2381°F (1260°C to 1305°C). The clay vitrifies to a higher level at these elevated temperatures, resulting in an extremely dense and non-porous final product. Cone 10, which is roughly 2381°F (1305°C), is the most widely utilized cone number for high-fire stoneware kiln burning. Firing to Cone 10 produces a fully vitrified, strong, and long-lasting ceramic body, making it a popular choice for functional pottery and art pieces that require maximum durability and water resistance.

Uses for High-Fire Pottery

High-fire stoneware clay bodies are well-suited for practical pottery, dinnerware, and tableware items due to their high firing temperatures and low porosity. Because of their longevity and resistance to water absorption, they are suitable for objects that require frequent usage and washing. Furthermore, professional potters and ceramic artists use high-fire stoneware for producing high-quality, long-lasting works that serve both functional and aesthetic purposes. Porcelain figurines are commonly high-fired as well as porcelain jewelry.

Color Transformations in Firing High-Fire Pottery:

During firing, iron impurities in the clay react with oxygen and other elements in the kiln atmosphere. This reduction and oxidation process can produce a variety of colors, ranging from warm browns and reds to grays and blacks. The reduction firing process, in particular, can result in fascinating and unanticipated color changes, giving each item a one-of-a-kind appearance. In some white porcelain clays, the final product results are more translucent allowing for light transmission through the clay.

Surface Treatments for Firing High-Fire Pottery

Stoneware clay bodies have a wide range of surface finishes when fired at high temperatures. The vitrification at these temperatures results in a dense and smooth surface, which allows glossy glazes to attain depth and brightness. Artists may also use matte or semi-matte finishes to highlight the natural colors and textures of the clay body. The smoothness of porcelain clay bodies allows for metallic glazes and other specialty crystalline glazes to be utilized.

Electric Kilns for High-Fire Pottery

High-Fire Kilns for Beginners

For stoneware and porcelain firing, beginners may want to start with smaller kilns that provide ease of operation and precise temperature control, but finding a small kiln powered by household power that will reach Cone 10 can be difficult due to the power requirements to reach and maintain that temperature.

This means that only a small volume of space can be heated to a high-fire temperature. For stoneware and porcelain firing, beginners may want to start with smaller kilns that provide ease of operation and precise temperature control, but finding a small kiln powered by household power that will reach Cone 10 can be difficult due to the power requirements to reach and maintain that temperature. This means that only a small volume of space can be heated to a high-fire temperature.

Examples of kilns that can meet high-fire pottery temperatures and are able to be plugged into household receptacles are:

High Fire Electric Kilns for Intermediate / Advanced Potters

Intermediate and advanced potters need high-fire electric kilns that are medium to large in size and have state-of-the-art digital interface, touchscreen controllers. These kilns offer additional scheduling and program flexibility. Advanced potters will want to investigate larger capacity kilns that can accommodate larger pieces or several projects. Potters who want to advance their firing skills may invest in larger electric kilns with more modern control systems, such as several thermal control zones for exact temperature distribution and intricate firing procedures. These are the options we recommend:

High-Fire Pottery Glazes

High-fire glazes are designed to mature at higher temperatures than those seen in stoneware and porcelain firing. To accomplish correct melting and flow at high temperatures, these glazes frequently contain a higher amount of fluxing agents like feldspar or boron.

High-fire glazes are available in a variety of colors, textures, and finishes, such as glossy, matte, and crystalline surfaces. Some of these glazes will need to hold for hours to develop and will require kilns that can maintain temperatures for long periods.

Conclusion

In conclusion, understanding the kiln temperature firing ranges for pottery is essential for every ceramic artist and potter. Firing temperatures determine clay and glaze maturity, which affects ceramic product design and usefulness. Pottery firing ranges are low, mid, and high-fire, with temperatures ranging from 1,700°F (Cone 04-06) to as high as 2,700°F (Cone 9-10).

From low-fire to mid-range and high-fire, each firing range offers distinct advantages and artistic possibilities. Choosing the appropriate kiln and glazes for each temperature range can significantly impact the quality and aesthetics of the final ceramic pieces, making the knowledge of kiln temperature ranges an indispensable tool for potters and ceramic artists alike.