Pyrometric cone

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Pyrometric Cone

A pyrometric cone is a device used in the ceramics industry to gauge the heatwork (the combined effect of time and temperature) during the firing of ceramic materials. These cones are essential for ensuring that ceramic products are fired to the correct maturity, which affects their strength, durability, and appearance.

• History

The concept of pyrometric cones was developed in the late 19th century by Hermann Seger, a German chemist. Seger cones, as they are sometimes called, were designed to provide a simple and reliable method for measuring the heatwork in kilns.

• Composition

Pyrometric cones are made from carefully formulated mixtures of ceramic materials, including clay, feldspar, and other minerals. These materials are blended to melt at specific temperatures, allowing the cone to bend or deform at a precise point during the firing process.

• Function

Pyrometric cones are placed in a kiln alongside the ceramic ware being fired. As the temperature in the kiln rises, the cones absorb heat and begin to soften. At a specific temperature, the cone will bend to a predetermined angle, typically 90 degrees. This bending indicates that the desired heatwork has been achieved.

• Types of Pyrometric Cones

There are several types of pyrometric cones, each designed for different temperature ranges and firing conditions:

• Standard Cones: Used for general ceramic firing, these cones are available in a wide range of temperature ratings.
• Self-Supporting Cones: These cones have a built-in base, allowing them to stand upright without additional support.
• Large Cones: Used in industrial kilns, these cones are larger and more robust to withstand harsher firing conditions.

• Usage

To use a pyrometric cone, it is placed in a kiln with the ceramic ware. The cone should be positioned so that it can be easily observed through a peephole or kiln window. As the kiln heats, the cone will begin to bend. When the cone reaches the desired angle, the kiln operator knows that the firing cycle is complete.

• Importance in Ceramics

Pyrometric cones are crucial for achieving consistent results in ceramic production. They provide a visual indication of heatwork, which is more reliable than temperature alone. This is because the rate of heating and the duration at high temperatures can significantly affect the properties of the ceramic material.

• Limitations

While pyrometric cones are highly reliable, they do have some limitations. They are single-use devices, meaning they must be replaced after each firing. Additionally, they provide a measure of heatwork at a specific location in the kiln, which may not represent the conditions throughout the entire kiln.

Also see

- Kiln - Ceramic glaze - Firing (ceramics) - Thermocouple