If you’ve ever opened your kiln to find glazes running, colors off, or pieces underfired, you know how unpredictable firing can be. Even when you use the same settings, each load can behave differently. That’s because firing isn’t just about reaching a temperature—it’s about how heat builds up and acts over time, a concept potters call heat work.
Calibrating your kiln ensures that the heat work inside matches what your firing schedule is designed to deliver. For busy educators managing multiple classes, a well-calibrated kiln means fewer surprises, stronger results, and happier students.

Why Calibration Matters
No two kilns fire exactly the same, even when brand new. Small differences in wiring, firebrick, or thermocouples can cause one kiln to run slightly hotter or cooler than another. As the kiln ages, these differences often grow due to wear and thermocouple drift.

For busy educators managing multiple classes, a well-calibrated kiln means fewer surprises, stronger results, and happier students.

In a classroom setting, every project matters. Calibration restores balance, helping firings stay accurate, consistent, and predictable. It helps ensure:

• Glazes mature as expected
• Clay bodies reach full vitrification
• Consistent results across shelves and multiple firings
• Less wasted time and fewer ruined pieces

How to Calibrate: Step by Step

1. Choose a Typical Firing
Pick a glaze-firing schedule you use often as your reference. If you typically fire to cone 05, that will be your target cone.

2. Set Up Witness Cones
On each shelf, place a cone pack of three cones:
• One cone lower (guide)
• Your target cone
• One cone higher (guard)
For example, if your target cone is 05, your cone pack would include cones 06, 05, and 04.

3. Fire Normally
Run the kiln with a typical student load. Do not calibrate with an empty kiln—shelves and ware affect heat distribution.

4. Read the Cones
After the kiln cools completely, measure each set of cones using the Orton template:

• The target cone should bend to about 90 degrees.
• The guide cone should be fully bent.
• The guard cone should remain mostly upright.

• Cone Offset: Fine-tunes the entire kiln. A cone offset shifts the setpoint temperature for a specific cone in the controllerʼs default programs. Use this if the whole kiln consistently over- or underfires.
• Thermocouple Offset: Balances uneven zones. A thermocouple offset changes the temperature reading from a specific thermocouple, letting you adjust one zone (top, middle, or bottom) individually if it fires differently. (Available only in multi-zone kilns.)
• Manual Temperature Adjustment: For custom programs, raise or lower the final temperature if youʼre not using default controller schedules.

• The schedule used
• Cone results
• Any adjustments made

When Should You Calibrate?

• When the kiln is new
• After changing a firing schedule or speed
• When student work looks unexpectedly over- or underfired
• When changing/replacing elements and/or thermocouples

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