Because the firing process is one of the most crucial aspects of ceramics! Historically, wood or oil were commonly used as primary fuels due to their availability and low cost. However, as the cost of these fuels has increased, modern ceramic kilns are now turning more towards LPG (Liquefied Petroleum Gas) and natural gas.
If you're a potter looking to transition to gas fuel safely and achieve perfectly desired pieces, let's explore the techniques you need to master for kiln control.
1. Kiln Temperature Control
Typically, we use a device called a thermocouple to measure temperature. This reading is then compared to the set point temperature for the firing duration to check if the temperature rises steadily according to the firing schedule. Importantly, you shouldn't rely solely on temperature readings or gas pressure.
Here are some techniques to maintain a consistent firing temperature in every cycle:
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Organized Piece Arrangement: Consistently control the placement and spacing of pieces on the kiln car to maintain uniform density and distance.
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Follow the Original Firing Graph: Maintain the heating system according to the standard firing graph that has been tested.
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Regular Accuracy Checks: Thermocouples must function correctly and should be sent to a laboratory for annual calibration.
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Correct Installation Position: The thermocouple should not be placed too close to the burner or embedded in insulation. Instead, it should extend approximately 3 inches from the kiln wall or roof.
2. Kiln Atmosphere Control
For each firing cycle, a valve should be installed to accurately measure fuel consumption. This data is used to calculate the optimal fuel-to-air ratio for firing.
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If there is too much excess air: The kiln will lose energy, and the resulting heat will be below standard.
If there is too little excess air: Combustion will be incomplete, resulting in a dull ceramic glaze.
Once the correct ratio is determined, it can be used to adjust the air and gas supply at the burner, creating a precise balance between the heat energy supplied and the residual oxygen within the kiln.
3. Kiln Pressure Control
For a convenient and affordable device to measure kiln pressure, we recommend a "Liquid Manometer." The suitable pressure range for operation is approximately 2–3 mm WG (millimeters of water gauge).
Recommended Pressure Measurement Position: It should be placed at the point of lowest pressure in the kiln, such as the center of the kiln door at the bottom (slightly above the kiln car level), or at the joint of the roller bars in a 24-hour continuous roller kiln. Alternatively, the same opening used for oxygen measurement can be utilized.