When it comes to kiln firing an at home kiln, a little bit of preparation (as well as having the right equipment!) can have a big impact on the outcome of your project. In this blog, we’ll be walking you through all the steps of kiln firing – from prepping your kiln to safely removing your project after firing completes.
What Is Kiln Firing?
Kiln firing is the process of heating your kiln to specific temperatures over specific time intervals in order to have the intended effect on the medium you’re firing. The progression of these temperatures and time intervals is known as a firing schedule.
Firing schedules are input through your kiln controller – whether you’re using a manual controller that requires you to update temperatures in real-time or a programmable kiln controller that you program in advance to automatically execute your firing schedule. The kiln controller then cycles your kiln relays to regulate the current to your kiln’s elements, thus controlling its temperature.
Kiln firing has a wide range of potential applications, from heat treating knives to fusing glass.
Understanding Kiln Firing Temperatures
Kiln firing occurs at different temperature ranges, depending on the medium you’re firing, as well as your intended effects. Additionally, different types of kilns have different capabilities when it comes to firing temperatures. Below is an overview of different firing temperatures for different media.
Kiln Firing Temperatures for Ceramics
In ceramics, kiln temperature ranges are typically measured in cones. Pyrometric cones, a technology dating back to the age of kiln sitters, each have a number that corresponds with the temperatures they melt at.
Kiln firing ranges for ceramics range from 1112°F for Cone 022 to 2552°F for Cone 14. This temperature chart includes corresponding firing temperatures for the different cone numbers, as well as the ranges for earthenware, stoneware, and porcelain.
Kiln Firing Temperatures for Glass
Kiln firing temperatures for glass require a greater degree of specificity, both in terms of setpoint and ramp rate. Glass artists categorize temperature according to technique (slumping, casting, fusing, annealing, etc.) and glass “coefficient of expansion” (how fast glass expands based on changes in temperature). Glass thickness is equally important, but that has more to do with changes in hold times or ramp rates as opposed to temperature.
Kiln firing temperatures for glass typically occur at slightly lower ranges than for ceramic, with a 1490°F setpoint for full fusing 90 COE glass and a 900°F annealing setpoint.
Kiln Firing Temperatures for Heat Treatment
Temperatures for heat treatment depend on the critical temperature of the metal or alloy you’re firing. These can range from 1350°F for sterling silver to 2375°F for T2 tungsten. Some of the most commonly used alloys for knifemaking, like 1084 and 1095 steel, occur in the middle of that range, with critical temperatures of 1600°F.
Compared to firing schedules for ceramic or glass, heat treat firing schedules are the simplest. Typically, ramp rate isn’t a factor and there is only a single setpoint.
Steps for Kiln Firing
Once you’re familiar with the process, kiln firing can become second nature. But there’s definitely more to kiln firing than just loading your project and turning on your kiln! In the following section, we’ll be covering the different steps of kiln firing including:
- Prepping Your Kiln
- Loading Your Kiln
- Programming Your Kiln Controller
- Firing Your Kiln
- Unloading Your Kiln
Prepping Your Kiln
Before firing your kiln, it’s important to prep your kiln and make sure your studio space is ready for kiln firing. Firstly, it’s important to make sure your kiln is properly installed, on a level surface – with 36” of clearance from any combustible surfaces. We strongly recommend enlisting the help of a qualified electrician for any necessary electrical work during installation and to inspect your setup.
Before starting a kiln firing, you should do the following to ensure a smooth firing:
- Visually inspect the wiring to your kiln and the kiln elements to ensure there’s no corrosion or debris buildup. While you don’t need to do this before every single firing, it definitely can’t hurt! This should be done regularly.
- Vacuum the chamber of your kiln. Debris, dust, and glazes from past projects can reduce element efficiency, release harmful vapors, or diminish the finish of your project. Again, this isn’t something you have to do before every firing, but it should be done regularly.
- Make sure there is nothing on top of, close to, or inside your kiln. Kilns get hot! Accidentally leaving objects on top of, inside, or near your kiln can pose a major fire risk. Before any kiln firing, you should doublecheck to make sure you didn’t accidentally leave anything where it will be exposed to the temperature of your kiln.
- Keep a firing extinguisher near your kiln. Keeping a reliable fire extinguisher near your kiln is an important kiln safety precaution.
Loading Your Kiln
When it comes to loading your kiln, the process is slightly different depending on the medium you’re firing, but a couple general principles apply:
- Gently place your project inside the kiln. Nothing is worse than having a project break inside your kiln.
- If firing multiple pieces, evenly distribute them throughout your kiln. Even distribution ensures that there is adequate airflow and even temperature throughout your kiln.
- Leave adequate space between the pieces you’re firing. Both clay and glass expand when fired. Leaving 1/2” between ceramic pieces and 1/8” between glass pieces ensures that your projects aren’t jeopardized as they expand with heat.
- Ensure proper clearance between the project and the kiln. When loading your kiln, make sure to maintain the following clearances between your project and the components of your kiln:
- At least 1” of clearance above the kiln floor.
- At least 2” of clearance from your kiln elements.
- At least 2” of clearance from your thermocouples.
- At least 2” of clearance your kiln’s lid.
- Pay attention to the temperature of different areas of your kiln. The closer a project is to the elements, the faster it heats up! Generally, you should place projects closer to the center of your kiln – but it might be helpful to place them closer to the elements if you’re firing thicker ceramic pieces or going for a more aggressive glass fuse.
- Protect the floor of your kiln. If you’re glaze firing ceramic or firing glass, it’s possible that melted glaze or glass will drip onto the floor of your kiln. Coating your kiln floor in kiln wash or sand can make cleanup significantly easier.
Programming Your Kiln Controller
Properly programming your kiln controller with the correct firing schedule is essential to a successful kiln firing. Different firing processes for different media – whether you’re working with glass, ceramics, or metals – all have unique setpoints, hold times, and ramp rates.
Your kiln controller may come with preset schedules, or you may find recommended firing schedules from the manufacturer of your media. But you can find tons of information for different firing schedules online from Facebook groups, YouTube, and Reddit where other artists share their firing schedules.
Once you have the correct schedule, programming your controller is mostly a matter of being mindful of entering the correct information. At SDS Industries, our goal with the TAP Controller is to make entering and executing the correct firing schedule as easy as possible – with intuitive menus, touchscreen controls, large text displays, and the ability to create schedules remotely with TAP Kiln Control Mobile. Plus, TAP Controllers give you the ability to save and access an unlimited number of schedules – so that you’re able to easily replicate successful kiln firings.
Firing Your Kiln
Once you’ve programmed your controller, it’s time to start firing! If you’re using an advanced automatic controller, such as TAP by SDS Industries, then firing your kiln is an extremely streamlined process. You just press start on your kiln and your TAP Controller will automatically execute your kiln firing – with alerts and alarms and real-time updates and remote monitoring to your smartphone or tablet.
Even so, we recommend never leaving your kiln unattended during firing! And if you need to open your kiln lid to check the status of your project or to unload your kiln, you should always use safety glasses and heat resistant gloves.
Unloading Your Kiln
Unloading your kiln is another stage of kiln firing that varies by medium. For heat treatment, you’ll often need to open the kiln and remove your ware for quenching while the kiln is still at maximum temperature. In this case, safety is key. In addition to safety glasses and heat resistance gloves, you’ll want to use tongs to transfer your wares to the quenching medium.
For glass and ceramics, you should allow them to cool inside your kiln prior to removal. For ceramics, you should let your kiln cool to 125°F to 300°F prior to unloading. For glass, you shouldn’t open your kiln until it reaches 100°F and shouldn’t unload your kiln until the glass reaches room temperature. For both of these mediums, there’s a risk of thermal shock if you unload your kiln before it cools down adequately, which can cause your project to crack or shatter.
Upgrade Your Kiln Firing Experience with TAP by SDS Industries
Are you looking for the best possible kiln firing experience? TAP by SDS Industries has got you covered!
The TAP and TAP II Controllers by SDS Industries provide advanced, precise, and easy-to-use multi-setpoint controls for kiln and offer responsive controls and an intuitive graphical UI on a large, easy-to-read touchscreen and allow you specify ramp rates and hold times for each step for maximum convenience.
The soon-to-be-released TAP&Go is a single setpoint controller designed specifically for heat treat. With simplified controls and a more affordable price point, TAP&Go provides the fundamental functionality you need!
All of the TAP Controllers are compatible with any relay-controlled kiln or oven and integrate with the TAP Kiln Control Mobile app to maximize your productivity while always keeping you informed on the status of your project.
We invite you to explore our selection of programmable kiln controllers, standalones, and conversion kits on our online store. You can also purchase TAP Digital Controllers or TAP Controlled Kilns and Heat Treat Ovens through one of the following distributors:
- Evenheat
- Hot Shot Oven & Kiln
- Mobile Glassblowing Studios, LLC
- Jen-Ken Kilns
- Kiln Frog
- Sheffield Pottery
- Delphi Glass
