Basics

• Load your kiln to maximize uniformity: How to Load Your Kiln Properly
• Zone control improves the evenness of the kiln firing but it cannot compensate for everything.
• Check element resistance: How to test element resistance.
• Check relays: How to test relays.
• Do a paper test if you are getting very uneven results.
• Try switching to single-zone.

Why Calibrate Your Kiln?

Most people will be satisfied with the operation of their kiln right out of the box. However, for precise work, a kiln needs to be calibrated or adjusted to match the specific clay, how you load your kiln, the firing temperature, the kiln's characteristics and condition, and the thermocouples (as they age and drift in accuracy).

In general, "calibration" means aligning the electronic control system to reach the desired heatwork and match the corresponding pyrometric cones when firing clay.

Know Your Kiln

Each kiln is unique. Kilns can vary in brand, size, and even between identical models. Multiple factors can affect how a kiln fires, including:

• The health or age of the electrical components (elements, thermocouples, relays)
• Insulation thickness
• The distance from the elements to the center of the kiln
• How the kiln is loaded
• External conditions like voltage, temperature, and humidity in the room

It's important to understand that while the controls used in most kilns are perfectly acceptable for ceramics, they are not precision instruments.

Controls & Thermocouples

• The controls in ceramic kilns are typically accurate to about 1% of scale (+/- 25 F on a typical kiln.)
• The thermocouples can read +/- 10°F from the actual temperature even when brand new.  Even though L&L uses the "Special Limit of Error" wire, there are still all kinds of variations in the thermocouples, the thermocouple circuit, and the cold compensation on the control. See this on Wikipedia for more information on thermocouples.
• In addition, the most common Type K thermocouples will drift over time, primarily when used over 2000°F.
• Type S platinum thermocouples do not drift at those temperatures. Type S thermocouples are an option for your kiln, but are very expensive due to their materials.
• The temperature you see on the control will probably not be completely accurate. Even if the temperature reading is precise, it is only one piece of the puzzle.
• Over time your kiln's firing will become more consistent.  (except when the thermocouple begins to drift) Calibrating your kiln helps the kiln to fire more accurately.
• Note from 2003-2020, L&L kilns were made with thermocouples with a closed protection tube.  This created an expected offset.  Although this issue was adjusted in the preset kiln settings, the temperature reading still has a possibility to vary.  Meaning that the offset may need to be adjusted. 

Clay and Glazes

Consult your clay and glaze suppliers for their firing recommendations. Some glazes can be very particular about heatwork, while others are more forgiving. The main objective is to calibrate your kiln to the level of precision you need. Don’t overdo it—if you are satisfied with your glaze results, calibration may not be necessary. Additionally, be aware that clay and glaze can vary between different batches due to differences in manufacturing.

Heatwork

Ceramics and glazes develop from heatwork, which is a function of both time and temperature. For any given temperature, the amount of time spent at that temperature determines how much heatwork is done. Focusing on just one part of this equation can be misleading. Even if you know the exact temperature, you still need to determine how much time at that temperature will give you the desired result.

Loading Your Kiln

How you load your kiln significantly affects how heat reaches and impacts your work.

• Avoid Firing an Empty Kiln: This can prevent the kiln from reaching temperature, resulting in an error code.
• Don't Overload: Avoid loading too densely or heavily at the top or bottom, as this can also cause an error code.
• Balance the Load: Load the kiln with a reasonable amount of work, ensuring pieces are not too close to the elements and are distributed as evenly as possible.
• Allow Space for Heat Circulation: Don’t place a shelf right next to an element. Most heating above 1200°F is radiant heat. Since not all work is exposed directly to the elements, make space for heat to circulate.
• Consider Heat Distribution: Allow time for the heat to move from the wall elements to the kiln's interior without overheating the work towards the outside.

There are guidelines for loading a kiln, but it often involves more art than science.

EMPTY KILN WILL NOT GET TO TEMPERATURE

• Sometimes, a new kiln does not get to temperature during the test firing due to the kiln being completely empty.
• Firing with your kiln furniture during the test firing will put some mass into the kiln and help it reach temperature.  

DIFFERENCES IN AN EMPTY KILN VS. FULL KILN

• An empty kiln cools a lot quicker, which will freeze the cone very quickly. In a full kiln, there is a lot of mass in the kiln that is just as hot as the kiln around it. It is this mass (the load in the kiln), which is radiating its heat as well, that will continue to melt the cone for a little longer after the kiln has been shut down.
• Once the kiln is fine-tuned, it is also how you have loaded the kiln that will account for many of the variations you will see from firing to firing. 
• Loading will affect the speed of firing - an empty kiln will fire differently than a full one. Although the control does compensate for this, the compensation is not totally perfect.

Cones

Pyrometric cones are essential tools for measuring ceramic heatwork. They are designed to bend at specific temperatures, indicating the amount of heatwork absorbed by the ware. Thus, they provide a more accurate representation of the ceramic process than the temperature reading on the digital controller.

Pyrometric cones offer the most reliable insight into what is happening inside the kiln. Using cones in addition to the control board allows for fine-tuning of the firing process to achieve the desired temperature. The placement of the cones within the kiln is important, as it influences their readings.

Calibrating the kiln with cones is your best method for achieving precise temperature control. However, remember that kiln calibration should align with the quality and appearance of your work, not just the readings of the cones.

FIRING A KILN WITH WITNESS CONES

Repeatable Results

• The only way to get entirely consistent results is to repeat the same process, with the same time-temperature cycle, with a kiln that changes as little as possible, and with the same materials as possible.
• This is how industrial ceramics is done but with far higher precision and with process engineers using statistics to process control.
• Most art ceramics have a much higher degree of variability.
• Achieving your exact desired results takes a tremendous amount of time and effort.  You have to be able to test, record results, and adjust when needed. Some of the crystalline ceramic artists are good examples of people who understand how to accomplish this.

How to Calibrate Your Kiln

Before calibrating the kiln, it is crucial to fire it to temperature with witness cones. This step allows you to accurately observe the kiln's temperature behavior, providing a solid starting point for calibration (note that kilns are not fired before shipping).

When firing the kiln, use witness cones and select the most typical or critical cone you use, typically your glaze temperature, as bisque temperatures are generally less critical.

Methods

There are two basic methods for calibrating your kiln: Thermocouple Offsets and Cone Offsets.

A Thermocouple Offset will change the temperature readings from room temperature to the kiln's maximum temperature uniformly.

A Cone Offset will only change the temperature for the specified cone.  For example, if you create a cone 6 offset for your glaze firing, it would not affect your cone 06 bisque firing. 

THERMOCOUPLE OFFSET

A thermocouple offset essentially adjusts the kiln’s perceived temperature to achieve the exact desired temperature. Here’s how it works:

• Positive Thermocouple Offset: This lowers the temperature in the kiln relative to the temperature reading on the control. For example, if the control reads 2000°F and you add 10°F of thermocouple offset, the control thinks there is 10°F more in the kiln. Consequently, for a setpoint of 2000°F, the kiln will actually control to 1990°F.
• Negative Thermocouple Offset: This raises the temperature in the kiln. For instance, if the control reads 2000°F and you subtract 10°F of thermocouple offset, the control thinks there is 10°F less in the kiln. Thus, for a setpoint of 2000°F, the kiln will control to 2010°F.

Thermocouple offset adjustments are available on Easy-Fire and custom programs with Dyna-Trol, One-Touch, and Genesis controls. All temperature readings in your control are determined by the thermocouple signal. Thermocouple readings can be inaccurate due to thermocouple drift or electrical noise (such as inductive current). The most reliable measure you can trust is a witness cone. When you change the thermocouple offset, you are not altering the control's setpoint, only the temperature interpretation via the thermocouple offset.

Think of the control setpoint as a constant, and the thermocouple signal reading as the variable adjusted during the offset process:

• Adding temperature to the thermocouple signal makes the control believe the kiln is hotter than it actually is, causing it to shut off sooner and fire cooler.
• Subtracting temperature from the thermocouple signal makes the control believe the kiln is cooler than it actually is, causing it to shut off later and fire hotter.

EXAMPLE AND PROCESS

• Witness cone bent slightly during the first firing, but no more than a little bit -- > Start by reducing the thermocouple offset setting by 5°F to make the kiln fire slightly hotter.
• Witness cone did not bend at all -- >  Start by reducing the thermocouple offset setting by 10°F to make the kiln fire hotter.
• Witness cone bent a little too much -- > Wait and see how it does with a full load or start by increasing the thermocouple offset by 5°F to make the kiln fire slightly cooler.
• Witness cone bent more than a little bit -- > Start by increasing the thermocouple offset settings by 10°F to make the kiln fire cooler.
• If the witness cone collapsed -- >  start by increasing the thermocouple offset settings by 15°F.
• There are beginning suggestions - feel free to experiment outside of this.

ANOTHER STARTING POINT METHOD

• To determine a good starting point for thermocouple offset (or cone offset) you can fire the kiln a cone or so hotter than your witness cone.
• Then carefully observe when the cone bends and note the temperature displayed on the control.
• Compare this number with what you think it ought to be using an Orton Cone Chart. You will have to have some idea of the speed of firing to get an accurate number.

THERMOCOUPLE OFFSET - GENESIS

THERMOCOUPLE OFFSET - DYNATROL

• Turn kiln on with toggle switch. Wait 5 seconds.
• Press 1, wait 5 seconds. The kiln display will say STOP and then go into IdLE mode.
• Press OTHER about eight times until you see TCOS
• Press ENTER. See TC 1
• Press ENTER again
• It will flash between °FOS (which stands for Deg F Offset) and 0018 (The 0018 stands for a thermocouple offset of 18°F - which comes preprogrammed into the control to compensate for the ceramic protection tubes. By changing the offset to 0010 we are REDUCING the offset by 8°F- making it fire 8 deg hotter). (NOTE: On older kilns, with a slightly different composition thermocouple protection tube the preprogrammed value is 0050).
• Press 0008 to reduce thermocouple offset by 10°F.
• Press 0013 to reduce thermocouple offset by 5°F.
• Press ENTER to accept your input.
• Do the same for all your thermocouples. The prompts will scroll past in the order of TC1, TC2 and TC3.

THERMOCOUPLE OFFSET - ONE-TOUCH CONTROL

• Access the Thermocouple Offset by getting into the Options.
• Options are accessed by holding the ENTER button while turning the power onto the control (turn on the kiln with the toggle switch) and continuing to hold onto the ENTER button until EdIt is displayed.
• This activates the Options Menu.
• The first thing you will see after turning the power on while pressing ENTER is LL-G or 1t-1 (This is the software version).
• Then you will see 1288 if it is a Cone 10 control or 1249 if it is a Cone 6 control.
• Then you will see EdIt, and you will hear a beep. You can now let go of the ENTER button.
• Press ENTER again. You will see °F or °C.
• Press ENTER again, and you will see OFFS
• Press the UP arrow to enter a positive offset OR press the DOWN arrow to add a negative sign to the offset. All this first button press does is get you in the right range.
• You can NOW use the UP or DOWN arrow to change the value of the offset. 
• When in the positive range, you can only go as low as 0000. The UP arrow increases the offset setting, and the DOWN arrow decreases it.
• When in the negative range, you can only go as high as -000. The UP arrow, when you are in the negative range, is moving the setting in the negative range. For instance, if you start at -000 and hit the UP arrow, you will be at -001 (negative by one degree). If you hit the DOWN arrow, you will go back to -000 (which is actually in the "positive" direction). Some of this is counterintuitive, so it takes some getting used to by just experimenting.  
• Once you are done with your setting, hit ENTER, and in a few seconds, the control will flash between IDLE and some temperature and STOP.
• If you want to redo the offset setting, turn the control off and start over.
• Older kilns with closed-end protection tubes came with a pre-programmed +18 Deg F offset to compensate for the thermocouple protection tube. Newer kilns with open-end protection tubes do generally not need an offset (except for fine adjustment).
• Note that the control does not convert the offset setting to deg C or F. If you are operating in Deg C then the offset setting should be +8 Deg C.
• Note: If you first press the DOWN button, you can only set a negative value, or if you first press the UP button, you can only enter a positive value.
• You can go back and change this later if you make a mistake. 

ADJUSTING TEMPERATURE VARIATION - TOP TO BOTTOM IN THE KILN 

• Note that you can use different Thermocouple Offsets for the three (or two) different thermocouples. 
• This allows you to make the top or bottom hotter or cooler to even out the temperatures in a kiln.

 

CONE OFFSET - GENESIS

CONE OFFSET - DYNATROL

1. Tune your kiln using the Thermocouple Offset for your most critical firing (typically glaze firings). 
2. Typically, bisque firings are not very critical. 
3. CNOS (Cone Offset) - is used to fine-tune what the Dynatrol thinks the final cone temperature should be in EASY-FIRE programs. The final cone temperature can be raised or lowered to a maximum of 99°F (or 55°C). When entering the offset temperature, the following code is used: the left two digits designate whether to raise (00) or lower (90) the cone temperature, that is, “00” means plus (+) and “90” means minus (-). The right two digits are the number of degrees the cone temperature will be raised or lowered. This offset will remain programmed only for the specific cone number until you reprogram the cone offset differently

 ONE-TOUCH CONTROL

• There is no Cone Offset Option on the One-Touch Control

Examples:

Number	Meaning
0020	Raise the final cone temperature by 20°F
0040	Raise the final cone temperature by 40°F
9030	Lower the final cone temperature by 30°F
9005	Lower the final cone temperature by 5°F

NOTE: This option does not affect the VARY-FIRE (Ramp-Hold) mode but it will show up on the menu.

NOTE ABOUT PREPROGRAMMED CONE OFFSETS:

• The Cone Offsets come preprogrammed. From cone 022 to cone 017 the cone offsets are set at 9020. All other cones are preset at 0000.
• Note on Blue DynaTrols made before Oct 1 2004, the cone offset was 9030 for cones 022 to 017 and 9020 for other cones. (The offsets were changed when we switched to a more responsive thermocouple protection tube).
• You can always change offsets.
• The RESET option in Other menu will NOT reset these cone offset settings.
• This is part of the compensation necessary for the mullite thermocouple protection tubes.

Cone Offset Example:

Adjust cone 07 to shut off the kiln at 20°F below Orton’s prescribed cone temperature.

Press	Display	Comment
OTHER OTHER	CNOS	If CNOS does not show on the display, press the Other key until CNOS displays.
ENTER	Alternately flashing: CONE & #	Cone Offset has been selected; the word CONE and the last entered cone number will alternately flash on the display. Now enter the cone number which you want to adjust (in this example cone 07)
07	Alternately flashing: CONE & 07	The word CONE and the entered cone number (07) will alternately flash on the display. If you type a wrong number, press 0 three times, press ENTER, then type the correct number.
ENTER	Alternately flashing: °F0S & 0	°F0S and the previous offset setting alternately flash. Enter the new offset temperature using the rules above, in this example, 9020
9020	9020	The selected offset temperature is displayed. If you type a wrong number, press 0 four times, then type the correct number.
ENTER	IdLE flashes then the current temperature	IdLE indicates the offset temperature adjustment has been accepted. The current temperature then flashes in the display.

 

TROUBLESHOOTING WITH CONES

See our various instruction sheets about cones, specifically troubleshoot-cones.pdf.