Pottery firing is the process of heating clay to transform raw clay into ceramic. Potters and ceramicists use pottery kiln temperature controllers to control the temperature of their kiln throughout the firing process to ensure that their pottery comes out hard, durable, and error free.
Before getting into the nitty gritty of how to operate a pottery kiln temperature controller, we’ll be exploring a general overview of the pottery firing process.
The 3 Stages of Pottery Firing
Regardless of the type of clay you’re using, pottery firing typically requires 3 basic steps:
Step 1: Drying
Raw clay is naturally moist. However, if you fire pottery before drying out the clay, then the water turns to steam, possibly resulting in fissures, cracks, or blow outs. Prior to pottery firing, it’s necessary to get the clay as dry as possible. This process is known as drying.
Some potters prefer to let their clay air dry, which typically take 24 to 48 hours depending on the thickness of the clay. However, there are ways to speed up the drying process, such as using a dehydrator, a desiccant chamber, or even using a hairdryer on low heat.
Even once the clay feels dry there is often still moisture trapped deep within the clay, so many potters do what’s known as candling or water smoking. Candling is when you heat your pottery in a kiln at low temperatures (typically around 122° F) for a prolonged period of time in order to eliminate moisture. When candling clay, it’s super important to keep your kiln below 212° F. Anything higher than that, and the water inside the clay boils, turns to steam, and can cause your pottery to explode – which is obviously no bueno!
Step 2: Bisque Firing
Once the clay is mostly dry, it’s time to perform what’s known as a bisque firing. Bisque firing is when you fire the clay at a higher temperature to turn the clay into ceramic! During bisque firing, the clay vitrifies – or becomes glass-like. While raw clay is moist, moldable, and water-soluble, ‘bisqueware’ is hard, brittle, and won’t dissolve in water.
During a bisque fire, the properties of the clay change as the pottery is heated to increasingly higher temperatures:
- At approximately 660° F, the clay becomes bisque. Water molecules that were chemically bonded to the clay are driven off. At this stage, the clay becomes fully dehydrated or ‘bone dry.’
- At around 930° F, the clay becomes ceramic. This means that its chemical properties are permanently changed and it can no longer dissolve in water.
- Between 1730° F and 1832° F, the clay becomes sintered. This means that the particles on the surface of the pottery are bonded together, increasing in hardness and density. However, the surface is still porous enough to accept glazes.
To avoid breakage, it’s important that the clay is slowly brought up to temperature and then allowed to cool slowly. A pottery kiln temperature controller allows potters to input the Setpoint (the temperature of the kiln) and the Ramp Rate (how quickly the kiln is heated up) to ensure that the pottery firing is successful.
Step 3: Glaze Firing
Once the bisqueware is fully cooled, potters and ceramicists apply glazes to the outside of the pottery to add color, change texture and finish, or to make the pottery water resistant or waterproof. Often, several layers are needed.
Once glaze has been applied and allowed to fully dry, the pottery is fired a second time. This is known as glaze firing. Glaze firing is typically done at the same temperature as the bisque firing, or slightly lower. Glaze firing at a higher temperature than the bisque firing can result in defects, blisters, bubbles, a cloudy finish, or other imperfections in the glaze.
The Role of a Pottery Kiln Temperature Controller
A pottery kiln temperature controller is the device that is used to manage the temperature of the kiln during a pottery firing. For electric kilns, automatic kiln controllers allow potters and ceramicists to preprogram their kiln to reach specific temperatures at specific time intervals.
Using Pottery Kiln Temperature Controllers to Create a Firing Schedule
The most advanced pottery kiln temperature controllers – such as the TAP and TAP II Controllers by SDS Industries – use an intuitive touchscreen interface to allow users to create the schedule for their pottery firings.
A schedule is a list of steps for each stage of the firing schedule. Each step includes:
- Step #: The order in which the steps of the schedule occur.
- Ramp Rate: The speed at which the kiln is heated or cooled (typically measured in degrees per hour).
- Setpoint: The maximum temperature the kiln reaches during this step.
- Hold Time: The length of time the kiln stays at temperature.
You can check out various sample schedules for firing ceramics here, courtesy of the Ceramic Arts Network. However, it’s important to follow the setpoint instruction for the type of clay you’re using, as well as the specific glaze. Pottery firing schedules aren’t one-size fits all!
Pottery kiln temperature controllers allow potters and ceramicists to create, name, and save different firing schedules for candling, bisque firing, and glaze firing. These can be easily edited to create specific schedules for different types of clays and glazes.
Pottery Firing with a Pottery Kiln Temperature Controller
Once the schedule has been created, the artist simply loads their piece into the kiln and presses ‘Start.’ At this point, the pottery kiln temperature controller automatically takes care of the rest, ensuring that the pottery is fired at the correct temperature from beginning to end.
However, for additional peace of mind, potters can use their pottery kiln temperature controller to set alerts or alarms to let them know when the kiln has reached specific stages in the firing process.
Using a Mobile App to Monitor and Control Your Pottery Firing
Additionally, today, potters and ceramicists have the option to monitor and control their pottery firing schedule from the convenience of their smartphone or tablet.
The TAP Kiln Control Mobile App, available on iOS and Android, integrates with pottery kiln temperature controllers to let potters:
- Monitor their kiln remotely with real-time updates.
- Skip firing steps or abort firings.
- Receive real-time firing updates.
- Create and modify schedules.
- View firing logs with by the minute data points.
- Update kiln settings.
- And more!
By upgrading to a premium subscription, TAP Kiln Control Mobile App users unlock additional convenience and quality-of-life features like Remote Start!
What is a PID Control Algorithm?
When firing pottery, temperature precision plays an important role in ensuring consistent outcomes. Pottery kiln temperature controllers that utilize a PID, or “Proportional Integral Derivative,” control algorithm, detect and compensate for discrepancies between input temperature and the temperature of the kiln. Basically, this means that PID controllers are extremely precise in reaching (and maintaining) specific temperatures during the firing process, minimizing the possibility of errors.
TAP Digital Kiln Controllers and Standalones utilize PID control algorithms, along with high quality components and preventative maintenance alerts, to ensure that potters and ceramicists can focus on their craft, without having to worry about the performance of their kiln.
Learn More About the Most Advanced Pottery Kiln Temperature Controllers
For pottery firing, the TAP and TAP II Controllers by SDS Industries are the most advanced, precise, and easy-to-use controllers on the market today. With responsive touchscreen controls, an intuitive graphical UI, and cutting-edge kiln controller software, TAP Kiln Controllers can pair with any relay-controlled kiln or oven.
We invite you to explore our selection of pottery kiln temperature controllers, standalones, and conversion kits on our online store. You can also purchase TAP Digital Controllers or TAP-Controlled Pottery Kilns through one of the following distributors:
- Hot Shot Oven & Kiln
- Mobile Glassblowing Studios, LLC
- Jen-Ken Kilns
- Kiln Frog
- Sheffield Pottery