How to Fire an Electric Kiln: The Basics & More
Firing a kiln is crucial despite not being the most visually captivating part of the process because it solidifies the artistic effort invested in earlier stages, resulting in a strong, usable final product.
Electric kilns are the most popular choice for firing because they are easy to find and set up. Thus, mastering their operation is a vital skill for artists. To help you achieve excellent results with your electric kiln, we’ve put together a guide on the basics of firing an electric kiln. Let’s get started!
Methods to Fire an Electric Kiln
1. Electric Kiln Controller
An electronic controller manages both the heating and cooling of the kiln. It can also perform a controlled cooldown. Users have the option to select a pre-programmed Cone Fire mode or create custom firing segments. The pre-programmed settings automatically increase the temperature when the pieces can handle rapid heating and decrease it when the clay needs slower firing.
To decide when to shut off the kiln, the controller relies on temperature charts to estimate when the appropriate heat work, or cone level, has been achieved. This estimation can vary depending on factors like the load density. Therefore, it's essential to periodically check your firings using witness cones inside the kiln until you're confident in their performance. This process will help you determine if any adjustments are necessary to reach the desired cone level.
2. Kiln Sitter / Semi-Automatic
Firing an electric kiln using a kiln sitter is a semi-automatic method suitable for ceramics, glass, and some metalwork. To begin, load your projects into the kiln and select a small pyrometric cone matching your desired firing temperature. A pyrometric cone is a small pyramid-shaped ceramic object used to measure and monitor temperature and heat work in kilns during firing processes.
Place this cone in the kiln sitter mechanism near the peephole. After closing the kiln, turn it on and set the switches according to your firing schedule. As the kiln heats up, the cone will soften and eventually bend enough to trigger the kiln sitter, automatically shutting off the kiln.
While the kiln sitter offers some automation, monitoring is still important, especially for non-ceramic projects that may require precise temperature control. For glass or metal work, you might need to manually adjust heating rates or hold times at certain kiln temperatures. The kiln sitter method is simpler than manual firing but less precise than digital controllers. It's particularly useful for standard ceramic firings, though it can be adapted for other materials with careful monitoring and manual adjustments. After shutdown, cooling typically happens naturally but may need manual control for certain projects, especially glass work.
3. Manual
The manual method of firing an electric kiln applies to various materials, including ceramics, glass, metals, and enamels. When firing, you begin by carefully loading your projects, whether they're pottery, glass pieces, or metal works, ensuring proper spacing and arrangement. You then close the kiln and start the heating process by manually adjusting the temperature controls.
Heating is typically done in stages, with a slow initial warm-up to prevent thermal shock. For glass projects, this slow start is particularly crucial to avoid cracking. As you increase the temperature, you'll need to closely monitor the kiln using pyrometric cones, a pyrometer, or by visually checking the color of the heat through peepholes, if available.
Different materials require different firing schedules; for instance, glass fusing might need precise temperature holds at specific points, while metal annealing requires careful control of both heating and cooling rates. Throughout the firing, you'll make frequent adjustments to the controls to maintain the desired temperature curve. This method demands constant attention and experience, as each type of project may require unique considerations in terms of heating rate, peak temperature, and cooling process. The firing duration can vary greatly, from a few hours for some glass work to a full day or more for high-fire ceramics. Once the firing is complete, you control the cooling rate manually, which is especially important for materials like glass that can be sensitive to rapid temperature changes.
Related: Best At-Home Kilns
Gas Kilns vs. Electric Kilns
Artists also like to use gas kilns, but there are key differences between gas kilns and electric kilns Electric kilns are easier to operate and provide consistent heat and precise digital control. This makes them ideal for home studios and oxidation firing. Electric kilns are quieter and cleaner but may have higher operating costs.
On the other hand, gas kilns can reach higher temperatures efficiently, allow for reduction firing (creating unique glaze effects), and are often preferred for large-scale production. They're more cost-effective to run but require more skill and proper ventilation. Electric kilns excel in temperature precision, beneficial for glasswork, while gas kilns provide faster heating and a more traditional firing experience. The choice depends on space, desired effects, production scale, and personal preference.
One important distinction is the use of kiln shelves. Kiln shelves are almost always used in electric kilns. Gas kilns also use shelves, but they aren’t as necessary and sometimes require a different configuration since gas kilns have a directional heat flow from burners.
Do Kilns Use A Lot of Electricity?
The consumption of energy by a kiln largely depends on the size, firing temperatures, and usage frequency of the kiln. A typical medium-sized electric kiln used for pottery can draw between 8,000 to 11,500 watts and consume 20 to 80 kilowatt-hours (kWh) per firing, depending on the duration and maximum temperature reached.
Smaller kilns might use less, around 1,800 to 6,000 watts, while large industrial kilns can consume much more. Read more on how much energy usage you’ll be using here.
Kiln Shelves Selection and Maintenance
Each kiln manufacturer has a recommended shelf kit for each model. If you’re using an electric kiln, choosing the right replacement kiln shelves is crucial for your firing projects. Incorrect shelf selection can lead to unnecessary expenses or even damaged shelves. When picking shelves, consider three main factors: the shelf material, the shelf thickness, and whether you need half-size or full-size shelves. Check to see what the manufacturer’s recommendations are and follow them!
To make the best choice, evaluate your kiln’s type and style, the firing temperature, the type of firing (such as oxidation, reduction, or raku firing), the glazing style, how often you fire, the weight of the ware, and your physical strength.
After selecting and using the kiln shelves, regular maintenance is essential. This includes applying kiln wash and periodically reversing the shelves to ensure even wear.
Bisque Firing
Bisque firing and glaze firing are two common processes that you can do with an electric kiln. We’ll start with bisque firing first and then move to glaze firing after.
To ensure a successful bisque fire, it is crucial to eliminate all water and humidity from the pottery. If the firing process is too rapid and the clay retains any moisture, the resulting steam can cause the piece to explode. This risk remains even when the clay appears dry, as moisture is still present within the clay molecules. Therefore, a slow bisque firing is essential.
For pieces that are not fully dry, or if you suspect dampness in the clay, consider candling them first. In a manual kiln, candling involves setting the bottom switch to low and maintaining that setting for eight to ten hours. For an electric kiln, program it to stay at approximately 82 degrees Celsius for the same duration. Candling effectively prevents breakage, even in thicker pieces. This method is particularly beneficial when firing work where clay thickness can vary significantly.
Crucial Reminder: Utilizing the candling feature in a computerized kiln can decrease the lifespan of the relays. Maintaining a temperature of 82°C for several hours causes the relays to activate and deactivate numerous times. However, if your kiln is equipped with mercury or solid-state relays, candling will have minimal to no impact on the longevity of the relays.
When bisque firing, it's crucial to allow steam to escape. If you have a kiln with a down-draft vent, the moisture can exit effectively. However, without a vent, you'll need to prop the lid open slightly using a kiln brick or a similar object during candling and the initial hours of firing. Typically, the upper peephole plug is removed during this period while keeping the kiln lid closed, and the top peephole plug stays out throughout the firing process.
Glaze Firing
Due to less clay water, glaze firings can go faster than bisque firings. Some glazes look better in fast firings than slow firings. The best fire speed depends on the glaze and may require experimenting. When firing damp, recently glazed pots, start slow if you're unsure of the best speed.
Similar to bisque firing, prop the kiln lid open for the first hours of firing or until it reaches 538°C if it doesn't have a vent. Additionally, the top peephole plug must be open during shooting. These processes are optional with a kiln vent system, which regulates airflow and moisture better.
You can restart the kiln if a power outage stops firing early. Cones will absorb heat and fall at the right temperature. With an electric kiln, outcomes will be close until the shutdown occurs in the last hour or two of firing when substantial heat work occurs. Check your witness cones to determine when to switch off the kiln if it turns off near the end.
Important Note: The same rules apply to bisque and glaze firing. Restarting is usually easy if the power fails early in the firing cycle. If the power fails in the final third of the fire cycle, the glazing results may suffer. The "refiring" effect can damage pots, make glazes sloppy, or cause crackling.
Kiln Safety During Operation
Given the high temperatures and potentially hazardous gases involved in kiln firing, artists need to prioritize safety. Here are key safety guidelines to follow before, during, and after firing:
Before the Firing
To safely operate an electric kiln, begin by acquiring proper protective gear, including kiln-specific safety glasses and high-temperature gloves. Thoroughly read your kiln's manual, focusing on electrical requirements and programming options. Install a kiln vent system designed for electric kilns, ensuring proper connection and outside ventilation.
Before each use, inspect kiln furniture for damage and apply fresh kiln wash if needed. Always unplug the kiln before loading, and verify that interior elements and the thermocouple are intact.
When loading, use kiln wash-coated shelves and ensure pieces don't touch the kiln walls or elements. Program your controller with the appropriate firing schedule, double-checking settings before starting. Monitor the firing through the peephole using safety glasses, never opening the kiln while hot. Allow natural cooling or use the kiln's cooling feature if available. By following these steps and your manufacturer's instructions, you'll maintain a safe environment and achieve successful firings with your electric kiln.
During the Firing
When operating an electric kiln, never touch the exposed heating coils or element connections to avoid severe electrical shock, which is a risk unique to electric models. Always monitor the digital controller during firing, watching for any error codes or unexpected temperature fluctuations. Never leave a kiln unattended.
Protect your eyes with welding-grade safety glasses when viewing the kiln's interior through the peephole, as electric kilns can reach extreme brightness. If you detect an acrid smell or see smoke, immediately shut off power at the circuit breaker and inspect the electrical components. Wear snug-fitting, non-synthetic clothing to prevent static buildup around the kiln's electrical systems. Avoid modifying the kiln's ventilation or adding insulation, as this can cause overheating of the electrical wiring and control box. Regularly check the condition of the elements, replacing them when signs of sagging or deformation appear to maintain even heat distribution. These precautions are crucial for safely operating an electric kiln and preventing electrical fires or damage to its sensitive electronic components.
After the Firing
After firing an electric kiln, allow it to cool completely before opening, as the elements can retain heat longer than in gas kilns. Always disconnect the power supply before unloading to prevent any risk of electrical shock, which is unique to electric kilns.
Keep the lid closed when not in use to protect the sensitive electronic components and heating elements from dust and moisture. Avoid placing items on top of the kiln, as this could damage the control panel or lid's electrical connections. Regularly inspect the power cord, plug, and control panel for signs of wear or heat damage, which are critical for electric kiln safety.
Maintain a clear space around the kiln, ensuring proper ventilation for the electrical components and preventing overheating. For longevity and safety, periodically check the condition of the elements and replace them as needed, as worn elements in electric kilns can lead to uneven firing and potential electrical hazards.
Fire an Electric Kiln Today!
Knowing how to fire an electric kiln is a crucial skill for bringing ceramic, glass, and metal creations to life. By mastering various firing methods and adhering to safety protocols, artists can achieve consistent, beautiful results. With practice, patience, and attention to detail, you'll unlock endless creative possibilities in your chosen medium.
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