Pyrometric cone

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Pyrometric cone

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Pyrometric cones before and after firing

A pyrometric cone is a device used to gauge the heatwork (the combined effect of time and temperature) in a kiln during the firing of ceramic materials. These cones are composed of ceramic materials that are designed to melt at specific temperatures, providing a visual indication of the heatwork achieved during the firing process.

History

The development of pyrometric cones can be traced back to the late 19th century. They were invented by Hermann Seger, a German chemist, who sought a reliable method to measure the heatwork in kilns. Seger's cones, also known as Seger cones, became widely adopted in the ceramics industry.

Composition and Function

Pyrometric cones are made from a mixture of ceramic materials, including kaolin, feldspar, and other minerals. These materials are carefully formulated to melt at specific temperatures. The cones are typically shaped like elongated pyramids and are placed in the kiln alongside the ceramic ware being fired.

As the temperature in the kiln rises, the cones begin to soften and bend. The degree of bending indicates the amount of heatwork that has been applied. This allows potters and ceramicists to determine whether the desired firing conditions have been achieved.

Types of Pyrometric Cones

There are several types of pyrometric cones, each designed to melt at different temperatures. The most commonly used cones are the Orton cones, which are manufactured by the Edward Orton Jr. Ceramic Foundation. These cones are numbered according to their melting temperatures, with lower numbers indicating lower melting points and higher numbers indicating higher melting points.

Applications

Pyrometric cones are used in various applications within the ceramics industry, including:

• Pottery: To ensure that glazes and clay bodies are fired to the correct temperature.
• Porcelain: To achieve the high temperatures required for vitrification.
• Brick and tile manufacturing: To monitor the firing process and ensure product quality.

Advantages

The use of pyrometric cones offers several advantages:

• Accuracy: Cones provide a reliable measure of heatwork, which is more accurate than relying solely on temperature readings.
• Simplicity: They are easy to use and do not require complex equipment.
• Visual confirmation: The bending of the cones provides a clear visual indication of the firing conditions.

Limitations

Despite their advantages, pyrometric cones have some limitations:

• Single-use: Cones can only be used once, as they melt and deform during firing.
• Environmental factors: The accuracy of cones can be affected by factors such as kiln atmosphere and placement within the kiln.

See also

• Kiln
• Ceramics
• Glaze
• Vitrification
• Thermocouple