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Complete Guide to Kiln Firing Temperatures

A definitive guide for understanding kiln firing temperatures.

Whether you work in pottery, glass, or heat treat, kiln firing temperatures play a critical role in achieving your desired result. Reaching the correct kiln firing temperature during each stage of your firing schedule is the difference between successfully completing a project…or creating a total mess!

Why Are Kiln Firing Temperatures Important?

Changes in temperature affect the physical properties of a medium. Heat alters a medium’s molecular structure, potentially affecting its hardness, brittleness, malleability, color, water resistance, and more.

Every kiln firing and heat treat process involves exposing material to heat to transform its physical qualities to give it a desired set of characteristics. Whether that’s transforming green clay to bisque, tempering a blade, or casting glass to fit a mold!

Different materials undergo specific physical (and chemical) changes at specific temperatures – so kiln firing temperatures are super important and vary according to medium and technique.

Kiln Firing Schedules

However, kiln firing temperature isn’t the only factor affecting outcome. The relationship between changes in temperature over time is super important. That’s why kiln firing schedules define the following:

  • Step #: The order in which the different kiln firing temperatures occur.
  • Ramp Rate: The speed at which changes in temperature occur (measured in degrees per hour).
  • Setpoint: The desired temperature the kiln reaches during each step (measured in degrees).
  • Hold Time: The length of time (defined in days, hours, or minutes) the kiln stays at a specific kiln firing temperature before advancing to the next step.

Kiln firing schedules vary greatly in kiln firing temperatures, as well as complexity. For instance, normalizing steel for a handmade knife might only involve a single setpoint over a specific hold time. Whereas, bisque firing pottery might involve five different setpoints, each with a specific ramp rate.

In addition to increases in firing temperature, decreases in temperature are equally important. Often, heating up an object and then cooling it down too rapidly jeopardizes its structural integrity, leading to cracks and brittleness.

Kiln firing 1095 steel to 1600° F relieves internal stress and ensures uniformity, making it stronger and harder.
Normalizing 1095 steel to 1600° F relieves internal stress and ensures uniformity, making it stronger and harder.

 

Categorizing Kiln Firing Temperatures

There are multiple ways to categorize kiln firing temperatures – whether by temperature range, material, process, or cone temperature. Artists in different media generally have different ways of categorizing kiln temperature:

  • Heat Treat: By and large, heat treat artists categorize kiln firing temperatures according to process (hardening, normalizing, tempering, etc.) and material. There are very few “one-size-fits all,” standardized ranges or schedules – specificity is key.
  • Kilnformed Glass: 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.
  • Pottery and Ceramics: For pottery and ceramics, kiln firing temperatures are still largely categorized based on cone firing temperatures and ranges – which we’ll be covering more in-depth below! Each ceramic material is rated for a cone that corresponds with a specific temperature, allowing for a more standardized scale.
For a full fuse kiln firing for 90 COE glass, the kiln must reach a setpoint of 1490° F.
For a full fuse kiln firing for 90 COE glass, the kiln must reach a setpoint of 1490° F.
 

 

 Understanding Cone Firing Temperatures

 

Unlike heat treat and glasswork, which require a greater level of specificity, potters deal in pre-defined temperature ranges – which correspond with pyrometric cones. Before the advent of modern programmable digital kiln controllers, kiln temperature control relied on manual kilns and the use of pyrometric cones and kiln sitters to measure when the proper kiln firing temperatures were reached.

Pyrometric cones melt at specified temperatures, providing a range for measuring (and categorizing) kiln firing temperatures. So, for instance Cone 06 for “low fire” clay softens and bends at 1832° F (1000° C), while Cone 14 for “high fire” porcelain softens and bends at 2552° F (1400° C).

Today, digital kiln controllers and digital pyrometers have largely made pyrometric cones obsolete. But cone numbers are still widely referenced for categorizing kiln firing temperatures. While cone firing charts are predominantly used in pottery, they are still sometimes referenced for heat treat and glasswork.

Click the button below for an in-depth cone temperature chart – which notes firing temperatures for each cone and describes the changes clay undergoes at each temperature:

 

Kiln Firing Temperature Ranges in Pottery

As you can see on the cone temperature chart, there are also temperature ranges that are used to categorize kiln firing temperatures for clay. The ranges below also correspond with three different categories of clay: earthenware, stoneware, and ceramics:

  • Low-Fire Clays: Cone 06 – Cone 1: Low-fire clays, also referred to as earthenware, are fired at temperatures ranging between 1828° F to 2079°F.
  • Mid-Fire Clays: Cone 4 – Cone 6: Mid-fire clays, which can be earthenware or stoneware, are fired at temperatures between 2142° F to 2232° F.
  • High-Fire Clays: Cone 10 – Cone 14: High fire clays, which can be used for stoneware or porcelain, are fired at temperatures between 2345° F to 2552° F.
Cone 04 clay, which is a common “low-fire” clay, fires at a kiln firing temperature of 1945° F.
Cone 04 clay, which is a common “low-fire” clay, fires at a kiln firing temperature of 1945° F.

For an in-depth explanation of the different types of clay, check out “Kiln Firing Chart for Pottery and Ceramics [Infographic].”

How to Ensure Your Kiln Reaches the Correct Kiln Firing Temperatures

Now that you understand the importance of kiln firing temperatures, how do you ensure your kiln reaches the correct temperature? That’s where kiln controllers come into play! There are three general phases when it comes to using a kiln controller to manage firing temperatures:

  • Input: First, the user has to enter what temperatures the kiln needs to reach, usually through creating a firing schedule or selecting a pre-set schedule.
  • Execution: Next, the temperature controller automatically executes the schedule, ensuring the kiln reaches the correct kiln firing temperatures over the correct timeframe.
  • Measurement: Throughout the execution phase, it’s important that either the controller itself (or an independent pyrometer) is able to precisely record kiln firing temperature based on input from the thermocouple.

Different kiln control methods handle these three phases more or less effectively. For instance, some temperature controllers are able to precisely execute schedules but are so difficult to use from a User Experience (UX) standpoint that it’s hard to know if you input the correct kiln firing temperatures to begin with! Others allow for too much variability in response times or temperature overshoot, meaning the kiln might not reach the precise temperatures you need during execution. And most kiln controllers require the user to be physically present at the kiln at all times to monitor its temperature.

The TAP Kiln Controllers by SDS Industries were designed to solve all these problems – with a touchscreen and intuitive menus to help artists input the correct kiln firing temperatures, as well as PID control algorithms to ensure maximum precision in the execution phase. Furthermore, all of the products in the TAP Ecosystem include integration with the TAP Kiln Control Mobile app – allowing for artists to remotely control and monitor their projects from their smartphone or tablet!

Explore Temperature Controllers by SDS Industries

The TAP and TAP II Controllers by SDS Industries provide users the most advanced, precise, and easy-to-use temperature controllers on the market today. With responsive touchscreen controls, an intuitive graphical UI, and integration with the TAP Kiln Control Mobile app, TAP Kiln Controllers can pair with any relay-controlled kiln or oven.

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:

Shop the most advanced programmable digital kiln controllers for sale.
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How Much Do Kilns Cost? The True Costs of Owning a Kiln

Description of kiln costs - from purchase and shipping to installation, operation, and maintenance.

For most artists, purchasing a kiln is a pretty big investment. Newer artists, especially, will probably have a lot of questions about what they’re getting into! How much do kilns cost? What about installation and kiln maintenance? Are kilns safe? What type of kiln is right for me? What kind of controller should I use for my kiln?

Don’t worry, we’ve got you covered! You can find our guides on kiln maintenance, kiln safety, types of kilns, and kiln control methods below. And by the end of this article, you’ll have a complete understanding of kiln costs!

Note: For the sake of this article, we’ll be primarily focusing on kiln costs for electric kilns, which are the most common kilns for the hobby kiln and studio kiln market. Gas kilns are typically more expensive, ranging from $3,000 on the extreme low-end to $30,000+ for a high-capacity gas kiln and have their own unique operating and installation costs.

Understanding Kiln Costs

When people think about kiln costs, a lot of the time they only think about the upfront cost of purchasing their kilns. While we’ll be covering purchase costs in depth, there are additional costs to consider. These include installation costs, kiln maintenance costs, material costs, as well as firing costs.

For the hobbyist, understanding these costs will help avoid unforeseen expenses. It will also help determine the most suitable type of kiln and possibly save some money! But for the professional artist, accurately tracking kilns costs can help make sure they’re pricing their wares correctly.

The Cost of Buying a Kiln

For most artists, purchasing a kiln is by far the most expensive part of kiln ownership. Kiln costs vary tremendously, ranging from around $700 for compact kilns to $20,000+ for large, higher powered, industrial grade kilns. There is also a robust used kiln market on Craigslist, eBay, Facebook Marketplace, and other online markets, where pre-owned kilns range from $275 to $3,000+ dollars.

Factors that influence kiln costs include:

  • Size: Generally speaking, the bigger the kiln, the more expensive – both at the time of purchase and in terms of potential installation, maintenance, and power costs.
  • Power Rating: Larger kilns and hotter kilns typically require more power and are generally more expensive.
  • Maximum Temperature: Generally, kilns with a higher maximum temperature are more expensive than comparable kilns with lower maximum temperatures.
  • Materials Fired: Glass kilns, ceramic kilns, knife kilns, and metal clay kilns (for jewelry) have different price ranges (which we’ll be covering more in-depth below).
  • Temperature Controller Method: The type of kiln controller that comes included with your kiln will impact its price by up to several hundred dollars – but your controller will have a major impact on your kiln firing experience and the functionality of your kiln.
  • Shipping Costs: As a larger item, shipping costs for kilns can add a substantial amount to your purchase price. When comparing prices between kiln suppliers, check to see whether shipping costs are included with the purchase of your kiln.

Whew, that may seem like a lot of factors to keep in mind! Don’t worry, we’ll be covering each of these considerations more in-depth. To help narrow your focus when purchasing a new kiln, it’s important to ask yourself the following questions:

  • How will I be using my kiln? What types of kiln firing schedules will I need to be able to execute?
  • Based on the media and techniques I use, what kiln firing temperatures and element placement will I need for my projects?
  • How big does my kiln need to be? How much space do I have to install the kiln at my home or studio?

The more specifically you can answer those types of questions, the easier it will be to determine which features you need to shop for and the kiln costs you should budget for.

Kiln Size Price Ranges

When it comes to buying a kiln, how big does your kiln need to be? Well, that depends…how big are the projects you’ll be firing? If you only need your kiln for slumping glass or firing jewelry or other small objects, chances are you’ll be able to save a lot of money on upfront costs and installation by purchasing a compact kiln.

However, if you’re firing large ceramic pieces – or firing multiple projects at a time – you’ll probably need to spring for a larger kiln.

Below are the average and median prices for kilns based on size (kiln prices throughout this article are based on aggregate price data from Kiln Frog).*

  • Compact Kilns: Under 15”
    • Price Range: $924.00 – $3318.54
    • Average Price: $1594.83
    • Median Price: $1474.16
  • Medium Kilns: 13” – 18”
    • Price Range: $916.00 – $4623.86
    • Average Price: $2028.56
    • Median Price: $1921.81
  • Large Kilns: 17” – 24”
    • Price Range: $1558.00 – $6889.54
    • Average Price: $3240.21
    • Median Price: $3139.00
  • X-Large Kilns: Over 24”
    • Price Range: $2416.00 – $25328.55
    • Average Price: $6669.63
    • Median Price: $4582.80

As you can see, the size of the kiln makes a big difference in price!

*Price data in this article includes current promotions – prices may vary.

Kiln Costs Based on Power Rating

Another factor that can influence kiln costs – for purchase, installation, and your electric bill – is the power rating of your kiln. When it comes to power rating, there are three ratings you need to understand: voltage, amperage, and wattage.

Voltage is the electric potential of a circuit. Comparing electricity to plumbing, voltage could be considered the pressure in a pipe. In the U.S., kilns typically come in two different voltage configurations: 120V and 240V, which correspond with the electric grid. 120V kilns are typically less expensive and match the voltage of a standard residential wall outlet; however, kilns exceeding 15 amps will need to be installed on a dedicated circuit.

A 240V kiln, on the other hand, needs a special wall outlet (other large appliances, such as wall ovens, AC units, and dryers use 240V outlets). Chances are, you will need the help of an electrician to run a new outlet in order to install your kiln. According to HomeGuide, this will cost anywhere from $250 – $800.

Amperage is the units of electrical current in a circuit. Extending the plumbing analogy, current is similar to the capacity of a pipe: the wider the pipe, the more water that flows. Kilns range from 13 amps to 80 amps. 120V kilns typically only go up to 30 amps, while 240V kilns can range anywhere from 30 amps to 80. At 48 amps or higher, a kiln will have to be wired directly into your power supply – another additional expense!

Watts measure the rate of power flow, calculated by multiplying voltage by amperage. Smaller 120V kilns typically draw between 1500 and 1800 watts, while a large 240V kiln can draw up to 11000 watts. TAP Kiln Controllers by SDS Industries allow you to enter your kiln’s watt rating, as well as the cost per kilowatt hour from your electric bill to automatically calculate your cost per firing.

The kiln costs tracking feature on TAP Kiln Controllers allows artists to automatically track how much they spend per fire.
The TAP Kiln Controller by SDS Industries allows artists to easily track their cost per fire on their electric kiln.

Kiln Costs by Maximum Temperature

Different kilns are capable of reaching different maximum temperatures. Generally, the hotter the kiln, the higher the kiln costs! If you need to fire Cone 14 porcelain, expect to spend more money than if you only need to fire Cone 06 ceramics. Reviewing these firing schedules for glass, ceramic, and metal heat treat can help you figure out which temperatures you’ll need your kiln to be able to reach based on the media and techniques you use.

Kiln Costs by Materials Fired

Speaking of media, when shopping for a new kiln, you’ll find that there are different kilns designed specifically for glass, ceramics, metal heat treat (for objects such as blades and knives), and metal clay (for jewelry and small metal trinkets). How do the materials you fire impact kiln costs?

Kilns have different dimensions and maximum temperatures based on the materials they’re designed to fire. Generally, metal clay kilns will be smaller than glass kilns, which will be smaller than knife kilns. Ceramic kilns tend to be larger and cylindrical, since you can stack pottery during fire. You can expect the price of the kiln to scale accordingly.

Additionally, ceramic kilns and heat treat kilns will typically need to be capable of reaching higher temperatures than metal clay kilns or glass kilns.

Broadly speaking, metal clay kilns will be the least expensive, and ceramic kilns will be the most expensive. Glass kilns and metal heat treat ovens often fall somewhere in between.

Temperature Controller Costs

Finally, an extremely important consideration when buying a kiln is deciding which brand and model of kiln controller to purchase with your kiln. After all, the kiln controller will be your primary interface with your kiln and will largely determine your user experience. Your kiln control method will determine the accuracy of your kiln firing, as well as what you can program the kiln to do.

Upgrading to a fully featured touchscreen programmable digital kiln controller will add a few hundred dollars to your kiln costs compared to a rudimentary 3-key model. Is it worth it?

In our opinion, yes. Definitively. An advanced, easy-to-use kiln controller like the TAP Kiln Controller gives you the ability to:

  • Easily navigate your controller and manage your firing schedules with just a few finger presses.
  • Name, save, and edit unlimited firing schedules with an unlimited number of steps per schedule.
  • Easily find and select the right schedule with alpha-numeric, full text displays.
  • Integrate your controller with the TAP Kiln Control Mobile App so that you can remotely monitor your kiln and create, modify, and execute firing schedules from your mobile device.
  • Enjoy peace-of-mind with push notification alerts and alarms to keep you informed of your firing status, notify you when it’s time for preventative maintenance, or let you know when unexpected conditions occur.

Additionally, SDS Industries is working on a lineup of more cost-accessible controller options that contain many of the advanced functions of TAP at a lower price point, with all kiln controller inputs performed via your smartphone.

Read our side-by-side kiln controller manufacturer comparison to compare the features of TAP against what you get with lower-priced controller options.

Additional Kiln Costs

In addition to kiln costs at point of purchase and installation, there are also longer-term costs to keep in mind.

We mentioned installation costs earlier. You should plan on budgeting up to $800 if you will need the help of an electrician in installing your kiln. Additionally, if you’re purchasing a ceramic kiln, you may need to buy and install a ventilation system which can run another $200 to upwards of $800.

For kiln maintenance, you will have to replace thermocouples, elements, and mechanical relays at regular intervals. Depending on how frequently you use your kiln and the temperatures you fire to, you should plan on budgeting at least $100 to $200 dollars every year or two to replace these components.

And, finally, you will have to budget for materials. Material costs can vary greatly per artist, but you should plan accordingly!

Conclusion

There you have it! Hopefully, this article has given you a full understanding of the true cost of owning a kiln. However, you should look at kiln costs as a long-term investment. If you take care of your kiln, it could last you for decades and give you countless hours of enjoyment and self-expression – so it’s hard to put a price tag on that! But it’s also important to know what you’re getting into and budget accordingly.

Explore Programmable Digital Kiln Controllers by SDS Industries

If you’re buying a new kiln, you’ll want to make sure it’s coming with the right controller. Ask your kiln supplier about TAP! The TAP and TAP II Controllers by SDS Industries provide users the most advanced, precise, and easy-to-use programmable digital kiln controllers on the market today. With responsive touchscreen controls, an intuitive graphical UI, and integration with the TAP Kiln Control Mobile App, TAP Kiln Controllers can pair with any relay-controlled kiln or oven.

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:

Shop the most advanced programmable digital kiln controllers for sale.

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Kiln Maintenance & How to Care for Your TAP Controller

Kiln maintenance helps prolong the lifespan of your kiln and its components.

Owning a kiln is a little bit like owning a car. With mindful operation and a little bit of routine maintenance, your kiln should last for decades! Proper kiln maintenance ensures your kiln remains safe and operational during that time.

The good news is that kiln maintenance is much simpler (and less expensive!) than maintaining your car. While a car has a gazillion different parts that will eventually need to be replaced, kilns have far fewer points of potential failure. And while it can be a good idea to occasionally enlist the help of an electrician or a kiln engineer (especially during installation), most kiln operators will be able to perform regular kiln maintenance by themselves!

Better yet, today’s programmable digital kiln controllers like TAP Controllers by SDS Industries include advanced diagnostics features and preventative maintenance alerts, so that you know when it’s time to replace kiln elements, thermocouples, and relays. That way, you’re able to maintain optimal performance without having to worry about your kiln conking out on you mid-project!

Routine Maintenance: Component Replacement

Just like with cars, there are certain kiln components that will wear down over time and will need to be replaced on a regular basis, so we’ll start with those first. These components include:

  • Thermocouples: Thermocouples – the probe that measures the temperature of your kiln – are regularly subjected to high temperatures. Over time, thermocouples become corroded and start crumbling at the tip and will no longer be able to accurately record temperature. You’ll need to replace your thermocouples on a regular basis – typically every 30 to 50 firings for Type K thermocouples.
  • Kiln Elements: Elements are the metal coils that line the inside of your kiln and heat up when they receive electric current. Over time, kiln elements become corroded and their resistance increases – meaning that they begin to become less efficient and require more electric current to heat your kiln. The lifespan of kiln elements can range anywhere from 1 to 5 years. Their lifespan depends largely on the type of kiln you’re using, the temperatures you regularly fire to, as well as firing frequency and duration.
  • Mechanical Kiln Relays: Kiln relays regulate the power to the elements of your kiln, allowing them to heat up or cool down. Mechanical relays, which come standard on most kilns, are subject to failure after around 200,000 cycles and will need to be replaced every 12-24 months. Alternatively, investing in mercury or solid-state relays can reduce kiln maintenance costs, since those relays last much, much longer. Mercury relays last around 5 million cycles and will only need to be replaced every 15-20 years. Finally, solid-state relays don’t have any moving parts and can last over 1000 years (TAP Kiln Controllers are compatible with all three relay types!).

Replacing these components is an inevitable part of kiln maintenance. TAP Kiln Controllers calculate health and life expectancy for each of these components based on user defined thresholds, letting you know when it’s time to replace each component to maintain optimal kiln performance.

Other kiln components that may require replacement include kiln bricks, kiln lids, electrical wires, and kiln controllers. However, there are steps you can take to monitor and prolong the lifespan for all of these components:

  • For kiln bricks, be careful when moving your kiln or when placing or removing objects from your kiln. Regularly visually inspect the interior of your kiln. Kiln bricks will need to be replaced when they’re no longer able to properly support kiln elements or when significant chunks of kiln bricks are missing affecting the thermal efficiency of your kiln.
  • For kiln lids, be mindful when opening and closing your kiln to prevent denting or damaging the lid. Do not lean on your kiln or use it as a shelf for storing objects.
  • Regularly inspect electrical wires for discoloration, brittleness, or corrosion. Immediately replace these components if necessary.
  • For kiln controllers, make sure they are properly installed and regularly keep the screen clean and free of debris. We’ll be going more in-depth on how to care for your TAP Controller further below!

TAP Kiln Controllers give users a detailed error log that helps them identify component failure. For a breakdown of error messages and troubleshooting steps, check out p. 12 of the TAP II Controller User Manual.

Maintenance tip for at home kilns

Kiln Maintenance: Installation

Ben Franklin once said, “An ounce of prevention is worth a pound of cure.” This is definitely true when it comes to kiln maintenance. Proper installation will prevent a ton of potential problems later down the road. Below are a few principles for kiln installation that will prolong the life of your kiln:

  • Select a space with adequate clearance and proper surfaces. Heat is a common cause of kiln component failure (or worse!). When installing your kiln, make sure your kiln has at at least 18” of clearance from non-combustible surfaces and 36” from combustible surfaces. Make sure the kiln is installed on a level surface that’s non-combustible and able to withstand high temperatures.
  • Install your kiln in a dry area. Water and electricity don’t mix! Installing your kiln in a dry area prevents shorts and surges and protects your kiln from corrosion, which will significantly reduce the life of your at home kiln components.
  • Follow manufacturer guidelines for installation. When you purchase your kiln, you should receive manufacturer guidelines for installation and kiln safety. Make sure to adhere to these closely when installing your kiln. If you purchase a used kiln, contact the manufacturer for installation guidelines.
  • Get any electric work done by a qualified electrician. At home kilns, especially larger ones, utilize a lot of electricity, so it’s important to make sure that you use a dedicated circuit with a properly rated power outlet and never use an extension cord. Enlisting the help of a certified electrician during installation helps reduce the likelihood of kiln maintenance problems down the road.
  • Make sure thermocouples are properly installed. Thermocouples help your automatic kiln controller precisely regulate the temperature of your kiln. However, thermocouples will only give you accurate temperature readings if they’re properly installed! Thermocouples should be inserted an inch or two into the interior or your kiln and should have at least 1″ clearance from any shelves, components, or any materials you place inside your kiln.
  • For DIY kiln builds, make sure relays are properly installed. Kiln relays ensure the safety of your kiln by cutting power to the elements if the kiln gets too hot. For DIY kiln or oven builds, it’s important to choose the right type of relay; for instance, solid-state and mercury relays will have far more longevity and reliability than mechanical relays. But it’s even more important to make sure that relays are properly rated and installed and that you utilize a safety relay to add redundancy in case one relay fails.
  • Don’t store your kiln outside. Since indoor kiln installation for ceramics and glazing requires proper ventilation, it might be tempting to keep your kiln outside. We strongly, strongly advise against that. Exposure to the elements will reduce the lifespan of your kiln and all of its components.

Kiln Maintenance Tips Before, During, and After Firing

While proper installation and regularly replacing necessary components can prevent a host of kiln maintenance issues down the line, there are also steps you can take before, during, and after firing to prolong the life of your kiln. Below is a list of tips for kiln care and maintenance!

  • Regularly clean your kiln. Debris, dust, and glazes in the interior of your kiln can reduce element efficiency, ultimately reducing their lifespan. Carefully dusting around the element grooves and regularly vacuuming your kiln’s interior helps prevent this. Just be careful not to damage the elements or the surrounding brick! If melted glaze gets on your kiln brick, make sure to gently scrape it off to avoid it absorbing into the kiln brick. You can also use kiln wash to minimize potential damage from dripping glaze (just make sure not to get it on the kiln’s elements!). Additionally, you should only clean your kiln when it is powered off to avoid causing electrostatic discharge if you accidentally hit the thermocouple and other mishaps.
  • Keep your lid closed between firings. Leaving your kiln’s lid open leaves it susceptible to dust, debris, or wildlife getting in (yikes!). Make sure to keep your lid closed when you’re not using the kiln.
  • Do not lean on your kiln. Leaning on your kiln can cause dents or stress fractures, reducing its efficiency.
  • Don’t use your kiln for storage. Storing items in your kiln can easily damage the bricks or elements of your kiln.
  • Be careful opening and closing your kiln. Be gentle opening and closing the lid of your kiln to avoid damaging the lid or the top-edge of your kiln.
  • Don’t open the kiln for prolonged periods when it’s still hot. While it may be necessary to occasionally open your kiln to monitor the status of your work during firing, prolonged exposure to abrupt changes in temperature can cause cracks and fractures in your kiln brick.
  • Regularly inspect kiln elements. Regularly visually inspect your kiln’s elements for debris buildup or corrosion. Occasionally, kiln elements may become dislodged from the grooves in the brickwork and may need to be repositioned. Additionally, you can use a multimeter to test their resistance. Once they exceed 10% of the recommended resistance in your kiln’s user manual, it’s time for them to be replaced.
  • Invest in a safety relay controller. The biggest threat to your kiln’s lifespan (as well as your safety and the welfare of your household and personal property) is too much temperature. Occasionally relays fail. If they fail in the open position, your kiln will keep heating up indefinitely. This is no bueno! Investing in a redundant safety relay controller like the TAP Monitor ensures that your kiln safely shuts off in case of relay failure.

Caring for Your TAP Controller

TAP Kiln Controllers are carefully manufactured from high-quality components and backed by an industry leading 3-year warranty. However, like any advanced electronic device, they are subject to failure, wear and tear, and their lifespan can be prolonged by proper care. Below are tips for caring for your TAP Controller:

  • Make sure your controller is properly installed. You can find tips for kiln controller installation for DIY builds here, but if you have any questions we encourage you to contact us.
  • Regularly clean your screen to keep it free from any dust or debris.
  • Avoid wearing jewelry or watch while using your TAP Controller, as these can result in scratches on the screen.
  • Again, we cannot stress this enough, do not store your kiln or your controller outdoors.
  • Regularly review diagnostic errors so that you can spot and troubleshoot potential errors with controller output.
  • Make sure your controller is updated to the latest software. If you’re connected to WiFi, updates will be downloaded automatically and you will be notified via pop-up. Simply follow the on-screen instructions. But you can find instructions for manually updating kiln controller software for your TAP Controller here.

Additionally, SDS Industries is always working to improve our kiln controllers and provide users with new features that improve their kiln firing experience. We’re currently working on an automated device monitoring software for TAP Controllers that monitors device performance and health. By monitoring various controller metrics, the software will be able to detect potential controller degradation so that we can be proactive and inform you if your controller needs repairs.

Maintenance tips and cleaning instructions for TAP Kiln Controllers by SDS Industries.

Tips for Cleaning Your TAP Controller

TAP Kiln Controllers use a resistive touchscreen for user inputs. As mentioned earlier, to maintain optimal performance, you should regularly clean your TAP Controller to ensure it’s free of dust, debris, smudges, and fingerprints. Below are a couple dos and don’ts for cleaning your TAP Controller:

  • Before cleaning the display, use a dry, lint-free microfiber cloth to gently wipe away any dust from the touchscreen.
  • Use distilled water to dampen the microfiber cloth to gently clean the touchscreen display.
  • Do not use the following cleaning agents: tap water, ammonia, acetone, ethyl alcohol, methyl chloride, or ethyl acid, as these can cause damage to your screen.

Explore Programmable Digital Kiln Controllers by SDS Industries

The TAP and TAP II Controllers by SDS Industries provide users the most advanced, precise, and easy-to-use programmable digital kiln controllers on the market today. With responsive touchscreen controls, an intuitive graphical UI, and integration with the TAP Kiln Control Mobile App, TAP Kiln Controllers can pair with any relay-controlled kiln or oven.

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:

Shop kiln controllers for electric kilns by SDS Industries.

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Kiln Firing Chart for Pottery and Ceramics [Infographic]

Kiln firing chart blog header

When it comes to firing ceramics, different types of clays and glazes are rated for different temperatures. A kiln firing chart, also known as a cone firing chart, is a useful tool for understanding the effects of temperature on different types of clays and glazes, as well as determining what firing schedule setpoints should be used depending on the cone rating of the media you’re firing.

What Temperature Is Pottery Fired At? Understanding Different Types of Ceramics

What temperature is pottery fired at? Well, that depends. There a three main types of clay that are used to make pottery: earthenware, stoneware, and porcelain. Each of these has different temperature requirements, as well as different properties once fired.

1. Earthenware

Earthenware clay is the most common type of clay used in ceramic firing today. Earthenware is softer than the other types of clay, making it easier to work with and more forgiving. Earthenware also has the lowest firing temperature requirements, which is why it was the first type of clay used to make pottery during the early stages of kiln history.

A collection of fired earthenware pottery to demonstrate the qualities of fired earthenware
Fired earthenware is porous and relatively soft. Earthenware ranges from white and gray hues to browns, oranges, and reds.

Firing Temperature

Earthenware clay typically reaches maturity (or optimum hardness) between 1745° F and 2012° F, although some low-firing earthenware clays can be fired in temperatures as low as 1200° F.

Cone Rating

Earthenware is what’s known as a “low fire” clay. Earthenware clay can be fired from Cone 015 up to Cone 1, but Cone 04 is the average.

Physical Properties

Since earthenware is fired at lower temperatures, it typically remains porous, relatively soft (you can scratch it with a knife!), and still absorbs water. Glazes are often required to make earthenware harder and watertight.

2. Stoneware

Stoneware is a “mid-range” or “high fire” clay that requires higher firing temperatures and a longer firing schedule than earthenware. Once it has been fired, stoneware is hard, dense, and rocklike – hence the name!

A collection of fired stoneware ceramics, demonstrating its hard, rocklike texture
Named for its hard, rock-like texture, fired stoneware is often gray or brown.

Firing Temperature

Stoneware reaches maturity between 2000° F and 2400° F – hotter than lava!

Cone Rating

Stoneware is typically fired between Cone 2 all the way up to Cone 12, with Cones 7 and 10 being the most common for mid-range stoneware and high fire stoneware, respectively.

Physical Properties

Since stoneware is fired at higher temperatures, it has time to fully vitrify, or form a glassy, nonporous bond on its surface. Finished stoneware is durable, hard, and nonporous. Unlike earthenware, stoneware is waterproof once fired even without the use of glazes.

3. Porcelain

Originating in China in 1600 BC, porcelain is a “high fire” clay that produces extremely hard, shiny, often white or translucent ceramics. Also known as kaolin clay (named after Kao-ling hill in China, where it was mined for centuries), raw porcelain is extremely dense and difficult to work. Often, porcelain is mixed with other types of clay to improve its workability.

A collection of fired porcelain ceramics, demonstrating its hard, glasslike white exterior
Fired porcelain is hard, smooth, and glasslike – notable for its white or translucent color

Firing Temperature

Porcelain typically reaches maturity between 2381° F and 2455° F – however, pure kaolin reaches maturity at 3272° F!

Cone Rating

Porcelain clay is fired between Cone 10 and Cone 13.

Physical Properties

Once fired, porcelain is extremely hard and fully vitrified, making it watertight and non-absorbent. Porcelain is noted for its distinct white color.

Understanding Firing Cone Ratings

As we mentioned earlier, different ceramic materials and glazes have a cone rating. Firing cones, or pyrometric cones, are a simple pyrometric device that indicate kiln temperature. Firing cones melt when exposed to a certain temperature for a prolonged period of time. Different ceramics and glazes are given a cone rating to indicate the temperatures at which they’ll reach maturity.

Firing cones range from 022 to 14, with 022 being the lowest temperature and 14 being the highest. As you’ll see on the kiln firing chart below, when a firing cone rating has a ‘0’ in front of it, a lower number indicates a higher fire temperature.

However, for firing cones without a ‘0’ in front of their rating, higher numbers indicate higher firing temperatures.

Kiln Firing Chart [Infographic]

In the kiln firing chart below, you’ll be able to see which temperatures correspond with various cone ratings and materials. The color gradient indicates the incandescence of the kiln at various temperatures, and the column to right indicates how the physical properties of ceramic changes at each temperature.

A pottery kiln firing chart, with temperature labels for each cones as well as insights for what changes occur in the clay at various temperatures.

Download PDF!

Reach the Right Setpoints on Your Kiln Firing Chart with Ease and Precision

The TAP and TAP II Controllers by SDS Industries are the most advanced, precise, and easy-to-use pottery kiln controllers on the market today. With responsive touchscreen controls, an intuitive graphical UI, and integration with the TAP Kiln Controller Mobile App, TAP Kiln Controllers can pair with any relay-controlled kiln or oven to allow you to easily manage and execute your kiln firing schedules.

We invite you to explore our selection of digital kiln controller, 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:

CTA to shop pages for pottery kiln temperature controllers.

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Understanding Kiln Firing Schedules for Glass, Ceramics, Pottery, and Heat Treat

Kiln firing schedules for glass, ceramics, pottery, and heat treat

The primary function of a kiln controller is to help users input (and successfully execute!) their kiln firing schedules…but what is a kiln firing schedule? Below, we’ll be helping you understand kiln firing schedules, as well as how firing schedules differ for materials such as glass, ceramic, pottery, and metal heat treat!

Definition of Kiln Firing Schedules

A kiln firing schedule is a progression of steps, made up of temperature changes over specific time intervals, that a kiln moves through during a firing. Each step of a kiln firing schedule is made up of four components:

  • Step #: Also known as a ‘segment,’ step # represents the order in which the steps of the schedule occur.
  • Ramp Rate: Measured in degrees per hour, the ramp rate is the speed at which the kiln is heated up or cooled down.
  • Setpoint: Measured in degrees, the setpoint is the desired temperature the kiln reaches during each step.
  • Hold Time: Also, known as a ‘soak,’ hold time is the length of time (defined in days, hours, or minutes) the kiln stays at a specific setpoint before advancing.

Each of these components determines the properties of the finished ware once the firing schedule reaches completion. Even extremely minor variances in adhering to kiln firing schedules can have a major impact on the finished result, so it’s important to accurately input firing schedules into your kiln controller and to utilize kiln controllers that are able to automatically execute kiln firing schedules with extreme precision.

Example of a Kiln Firing Schedule

Kiln firing schedules, sometimes colloquially referred to as programs or firing schedules, can best be described as the road map the controller uses to execute a firing. While kiln firing schedules can string together as many steps as necessary to achieve the desired firing result, below we’ll be looking at an example of a three-step firing schedule:

Example of a 3-step kiln firing schedule in order to illustrate the format and various components of firing schedules

Assuming the kiln starts at room temperature, or 70° F, the example schedule shown above will result in a firing that takes 5 hours and 24 minutes to complete. Below is a visual graph representing the firing profile of this schedule:

A 3-step kiln firing profile plotted as a line graph

In this graph, we can see that the kiln follows a 500 degree-per-hour ramp rate from time 0 (when the kiln was started) to 950 degrees (the first setpoint). Once the setpoint is achieved, the controller regulates the temperature to keep the kiln at 950° for 30 minutes.

Once the hold time from the first step is completed, the kiln advances at a rate of 1200 degrees-per-hour to a setpoint of 1425° and holds there for 20 minutes.

Finally, the kiln moves to step three, cooling at a rate of 300 degrees-per-hour down to a setpoint of 700°. Because the hold time at Step #3 is zero, the kiln firing schedule is now complete!

See our article on Alerts and Alarms so you can be notified when your kiln firing schedule reaches certain firing points! 

Ramp/Hold vs Time-to Temp Schedules

Kiln firing schedules can also be expressed in different formats. The example above is the common Ramp/Hold format, which can also be described as a Ramp/Soak or Ramp/Dwell schedule. This is the most common kiln firing schedule format, and it is also the format that is supported by TAP Kiln Controllers.

However, kiln firing schedules can also be written in a Time-to-Temp format, which contains all of the same information but prioritizes the timing of the firing as opposed to the temperature of the firing.

When generating a Time-to-Temp schedule, you are, in effect, saying “I want to be at 950 degrees in 1 hour and 45 minutes.” At that point, the controller is responsible for converting the defined “Time-to-Temp” into a usable Ramp Rate. By saying we want to be at 950° in 1 hour and 45 minutes, and assuming we’re starting from 70°, we’ve essentially created a firing schedule with an implied ramp rate of 500 degrees-per-hour.

NOTE: Some controllers that use Time-to-Temp format do not report accurate ramp rate, which can affect outcomes of the firing schedule. For instance, a Time-to-Temp controller might report that your kiln went from 100° to 1250° in one minute, because that was what it was programmed to do, even though achieving that level of temperature change over that time interval simply isn’t possible.

Below is the exact same kiln firing schedule from before written in a Time-to-Temp format:

A kiln firing schedule written in Time-to-Temp format

The firing graph for both formats would look exactly the same – and executing either format would yield the same outcome once the firing schedule reaches completion (assuming the controller was capable of converting the Time-to-Temp into an accurate ramp rate). The only difference is how the kiln firing schedule is expressed. What was defined in three steps in the Ramp/Hold format requires five steps in the Time-to-Temp format, despite yielding the same firing profile.

What Factors Does a Kiln Firing Schedule Depend On?

Kiln firing schedules are dependent on the material/media being fired, as well as the physical capabilities of the kiln. There is no one-size-fits-all approach to kiln firing schedules, as the material within the kiln will require its own unique schedule to achieve optimal results. Later in the article, we’ll be looking at examples of firing schedules for glasswork, firing ceramics, and metal heat treat.

Limitations of Kiln Firing Schedules

Now that you know the components of a kiln firing schedule, you should also understand the limitations. The physical capabilities of the kiln dictate certain physical boundaries that cannot be overcome. The material of the kiln, chamber size, power rating, and thermocouple gauge all contribute to the kiln’s demonstrated performance.

As kilns approach higher temperatures, their ability to heat at defined ramp rates begins to fall off. A kiln that can heat at a ramp rate of 3600 degrees-per-hour while at 200° will likely be unable to generate the same ramp rate at 1500°. This is a result of the kiln material and power rating.

Thermocouples are used to read the temperature inside a kiln chamber and communicate that temperature to the kiln controller. A kiln with an 8-gauge thermocouple will respond much slower to temperature input than a 20-gauge thermocouple. This can result in overshoot at low setpoints as the thermocouple needs time to “catch-up” to the heat that has been applied to the kiln.

Kiln Firing Schedules for Glass

While the kiln firing schedule example above was hypothetical, in this section we’ll explore actual kiln firing schedules for different types of glasswork techniques.

Please Note: Each of these schedules is for 90 COE glass. Additionally, each firing schedule will have to be adjusted according to your specific kiln, the size of your project, as well as the type of glass you’re using – some experimentation will be required, so please just use these as a general guideline.

For additional in-depth technical information about using your kiln to fire glass, please visit https://www.bullseyeglass.com/index-of-articles/.

Full Fuse Firing Schedule

A full fuse is when you use heat and time to combine two or more layers of glass to form one single solid piece of glass. The layers of glass fuse together – hence the name! Below is a full fuse firing schedule for projects that are smaller than 12”.

A full fuse firing schedule for 90 COE glass

  1. 400°F/Hr to 1250°F – hold 30 minutes.
  2. 600°F/Hr to 1490°F – hold 10 minutes.
  3. AFAP°F/Hr to 900°F – hold 30 minutes.
  4. 150°F/Hr to 700°F – hold 0 minutes.
  5. AFAP°F/Hr to 70°F – hold 0 minutes.

You can find temperature guidelines for additional glasswork processes here.

Glass Casting Firing Schedule

Glass casting is when you melt glass until it is soft and malleable enough to conform to a mold. The glass then hardens to create a glass object in the shape of the mold. Below is a glass casting firing schedule for a small open face mold cast:

A glass casting firing schedule for 90 COE glass

 

 

  1. 100°F/Hr to 200°F – hold 6 hours.
  2. 100°F/Hr to 1250°F – hold 2 hours.
  3. 600°F/Hr to 1525°F – hold 3 hours.
  4. AFAP °F/Hr to 1200°F – hold 4 hours.
  5. 50°F/Hr to 900°F – hold 6 hours.
  6. 12°F/Hr to 800°F – hold 1 minute.
  7. 20°F/Hr to 700°F – hold 1 minute.
  8. 72°F/Hr to 70°F – hold 1 minute.

Additional details about casting firing schedules can be found here.

Annealing Firing Schedule

Annealing glass is the process of stabilizing glass during the cooling process by holding it at a steady temperature to give it time to strengthen. COE 96 glass is typically annealed at a setpoint of 960°F. However, the size of the glass, its thickness, as well as the number of layers being used determines how long the anneal hold needs to be.

From the example of the Full Fuse Firing Schedule above, we highlighted the steps that involved annealing in green:

An annealing firing schedule for a glass kiln

Notice that Step #3 has the kiln hold at the annealing setpoint 900°F for 30 minutes in order to give the fuse time to stabilize, and then Step #4 and Step #5 have the kiln slowly cooling down from the setpoint to the final temperature.

See our article Benefits of Using a Digital Controller for Glass Kilns for more information about using your kiln for glasswork!

Kiln Firing Schedules for Ceramics

Before getting into kiln firing schedules for ceramics, it’s important to know what Cone # the material you’re firing is rated for. This represents the setpoint at which the type of material you’re using is properly fired. So, for example, Cone 04 clay would need to reach a setpoint of at least 1945°F whereas Cone 6 Porcelain would need to reach a setpoint of 2232°F.

Please Note: All of these kiln firing schedules are for 04 Cone clay. Just like with glasswork, each firing schedule will have to be adjusted according to your specific kiln, the size of your project, as well as the type of clay, stoneware, or porcelain you’re using – some experimentation will be required, so please use these as a general guideline.

Candling Firing Schedule 

Candling is the process of allowing clay to fully dry prior to high temperature ceramic firings. This involves heating your kilns to a low temperature for a prolonged period of time. Below is an example of a kiln firing schedule for candling your clay:

A pottery kiln firing schedule for candling clay

  1. 150°F/Hr to 150°F – hold 12 hours.

Simple, right? However, this is just to get the clay ‘bone-dry’ before firing it, since the natural moisture of the clay, if fired too quickly, can cause your project to crack and fissure!

Bisque Firing Schedule for Cone 04 Ceramics

A bisque firing is the process of turning clay into ceramics! Below is a slow bisque firing schedule for Cone 04 clay:

A bisque firing schedule for Cone 04 ceramics

  1. 80°F/Hr to 250°F.
  2. 200°F/Hr to 1000°F.
  3. 100°F/Hr to 1100°F.
  4. 180°F/Hr to 1695°F.
  5. 80°F/Hr to 1945°F.

You’ll notice that this firing schedule doesn’t include any hold times. However, the total firing time is 13 hours and 26 minutes. So how does that work? In this case, the firing time is dictated by the ramp rate – or the amount of time it takes for your kiln to reach each setpoint in the firing schedule.

Glaze Firing Schedule for Cone 04 Ceramic

When firing pottery, it’s important to match the Cone # of your glaze to the Cone # of your clay. In this case, we’re using Cone 04 clay, which is a “low-fire” clay. Therefore, we’d want to use a glaze that’s in the Cone 06-04 range. In other words, the temperature of the glaze firing schedule shouldn’t exceed the temperature of the bisque firing schedule.

Glaze firing schedule for Cone 04 ceramics

  1. 150°F/Hr to 250°F.
  2. 400°F/Hr to 1695°F.
  3. 100°F/Hr to 1945°F.

See our article on How to Use a Pottery Kiln Temperature Controller for more information on how to fire ceramics!

Firing Schedules for Heat Treating Metals

Just like with glasswork and pottery, kiln firing schedules for metal heat treat is extremely dependent on the type of material you’re using. But, additionally, it’s dependent on the qualities you want the finished metal to have. For heat treat, the rate at which you cool the metal has a significant impact on the molecular structure of the metal. For these examples, we’ll be working with 1095 steel.

Please Note: All of these kiln firing schedules are for 1095 steel. Just like with Each firing schedule will have to be adjusted according to your specific kiln or heat treat oven, the type of metal you’re using, its thickness, as well as the desired properties – some experimentation will be required, so please just use these as a general guideline.

You can find more information about setpoints and cooling rates for different effects on different types of metal here.

Normalizing Firing Schedule for 1095 Steel

Normalizing is a process where metal is heated to an extremely high temperature for a defined period of time and then either air-cooled or furnace cooled at a controlled ramp rate. Normalizing relieves internal stress and ensures uniformity, resulting in harder, stronger metals. Below is a normalizing firing schedule for 1095 steel:

A schedule for normalizing 1095 steel in a heat treat oven

  1. AFAP°F/Hr to 1600°F – hold for 15 minutes.
  2. Remove knife or blade from the oven and allow to air-cool.

Quench Hardening Firing Schedule for 1095 Steel

Quenching is the process where metal is heated and then cooled rapidly by dipping it into an oil, polymer, or water, resulting in very hard, very brittle metal. This increases the hardening of the metal (but also its brittleness). Below is a quench firing schedule for 1095 steel:

Heat treat schedule for quench hardening 1095 steel

  1. AFAP°F/Hr to 1600°F – hold for 15 minutes.
  2. Remove knife or blade from the oven and quench in fast oil to 150°F.

Tempering Firing Schedule for 1095 Steel

After hardening, the metal is heated to a lower temperature to reduce excessive hardness and relieve internal stress. Tempering makes metals less brittle – it should be done within two hours after the steel cools from the quench hardening process. Below is a tempering firing schedule for 1095 steel:

Tempering firing schedule for 1095 steel

  1. AFAP°F/Hr to 400°F – hold for 2 hours.
  2. Allow knife or blade to slowly cool – either air-cooled or within the oven.

You’ll notice that most heat treat applications have simple kiln firing schedules that only involve a single setpoint and aren’t dependent on ramp rate. For this reason, it might make sense to use a single setpoint controller for heat treat applications like the TAP & Go by SDS Industries.

Check out Guide to Choosing Heat Treating Controllers for more information about different types of heat treatments!

The Easiest Way to Precisely Execute Kiln Firing Schedules

The TAP and TAP II Controllers by SDS Industries are the most advanced, precise, and easy-to-use digital kiln controllers on the market today. With responsive touchscreen controls, an intuitive graphical UI, and integration with the TAP Kiln Controller Mobile App, TAP Kiln Controllers can pair with any relay-controlled kiln or oven to allow you to easily manage and execute your kiln firing schedules.

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:

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Types of Kilns: An Informative Guide for Kiln Users

Blog Header Image for Different Types of Kilns

Kilns have been used for millennia to create ceramic, glass, and even metal objects. As technology has advanced, so have kilns. Now, there are a wide variety of kilns available on the market for hobbyists and professionals alike. In this guide, we’ll explore the different types of kilns and their specific uses.

What Is a Kiln?

Before getting into the distinctions between the different types of kilns, let’s reach a broad definition for what a kiln is. A kiln is an insulated chamber that can be heated to very high temperatures for firing, burning, or drying of pottery, ceramics, glass, metals, or other materials.

Types of Kilns: Overview

As human civilization has evolved, the kiln has undergone many iterations. There are multiple ways to categorize kilns. For instance, you can categorize kilns based on power source, heat distribution, structure or technique, use-case or size, material fired, or control method. Below is a quick overview of the various types of kilns. Later in the article, we’ll be exploring the most common types of modern kilns more in-depth.

Types of Kilns Based on Power Source

  • Wood-Fired Kilns: Wood-fired kilns use heat from burning wood to increase the temperature of the kiln.
  • Coal-Fired Kilns: Coal-fired kilns, which used coal to replace wood for the fuel source, were widely used up until in the mid-twentieth century.
  • Gas Kilns: Gas kilns use natural gases or propane to heat materials and are capable of reaching high temperatures that exceed the temperatures of wood burning or electric kilns.
  • Electric Kilns: The most common type of kiln for artists and hobbyists, electric kilns use electric current to heat elements inside the kiln, offering more precise control over temperature.

Types of Kilns Based on Heat Distribution 

  • Intermittent Kilns: Intermittent, or periodic, kilns are only heated some of the time. With intermittent kilns, the ware is placed inside the kiln and the internal temperature of the kiln is increased or decreased based on a firing schedule. However, once the firing is complete, the ware and the kiln itself are allowed to fully cool.
  • Continuous Kilns: Continuous kilns are perpetually heated. Continuous kilns, or tunnel kilns, have a continuous heat source in the center. Ware is physically moved throughout the kiln, closer or farther to the heat source, to control its temperature. Continuous kilns are more commonly used for industrial processes.
  • Updraft Kilns: Updraft kilns are heated from the bottom of kiln and air is exhausted from the top.
  • Downdraft Kilns: More efficient than updraft kilns, downdraft kilns are also heated from the bottom, but the construction of downdraft kilns forces the hot air to recirculate the kiln rather than escaping from the top.

Types of Kilns Based on Structure or Technique

  • Pit Fire Kilns: The earliest iteration of the kiln, pit fire kilns are wood burning kilns that rely on earthen pits to provide insulation.
A pit-fire kiln.
The pit-fire kiln was the earliest iteration of the kiln.
  • Beehive Kilns: Beehive kilns, another early iteration of wood burning kilns, utilize arches to create a domed brick chamber for firing. Beehive kilns included baffles to regulate airflow and control the temperature of kiln, as well as holes at the top of the chamber (and later chimneys) to allow the heat to rise.
A beehive kiln in Death Valley, CA
Beehive kilns were one of the earliest evolutions of wood burning kilns.
  • Climbing Kilns: Climbing kilns were built into hillsides. A fire would be lit at the bottom and, since heat rises, the temperature of the kiln would increase with greater regularity, allowing for greater quantities of pottery to be fired.
A climbing kiln in Kyushu Island, Japan
Climbing kilns utilized changes in elevation to heat pottery with greater regularity. 
  • Soda Kilns: Soda kilns use large, arched chambers, with a chimney on one end, and are heated to high temperatures. During firing, sodium bicarbonate dissolved in water is sprayed onto the ware to form a glaze.
  • Sawdust Kilns: Sawdust kilns are simplistic kilns that consist of a small brick chamber where bisque is covered in sawdust. A grate is used to cover the top of the kiln, and the fire is lit on top of the grate.
  • Anagama Kilns: Originally invented in China and later brought to Japan, Anagama kilns are wood-burning kilns that consist of a sloped earthen structure with a single fire chamber on one end and a chimney on the other.
  • Noborigama Kilns: An evolution of the Anagama kiln, Noborigama kilns are multi-chambered wood-fired kilns that consist of a succession of chambers with a stoked fire at the lowest level. More efficient than Anagama kilns, Noborigama kilns capture and recirculate the hot air from previous firings.
  • Raku Kilns: Raku is a firing technique where the ware is removed from the kiln while the kiln is still hot. As such, Raku kilns must allow for the ware to be easily removed. Today, most Raku kilns are gas powered since electric kilns can be damaged by opening them when the kiln is at temperature.
  • Top Hat Kilns: Top hat kilns are designed so that the firing chamber is lowered down onto the wares and then raised again when firing is complete, often using a hand-crank.
  • Bottle Kilns: An evolution of the beehive kiln, bottle kilns (or bottle ovens) are coal-fired kilns made from brick that consist of a hovel that tapers into distinctive bottle-shaped chimney – hence the name! The unique shape of the bottle kiln improved draught while protecting wares from inclement weather.
Bottle kilns in Stoke-on-Trent, England
Named for their distinctive bottle-like shape, bottle kilns were widely used for industrial processes in England during the late 18th and 19th centuries.
  • Car Kilns: Typically used for industrial processes, car kilns utilize a static firing chamber, through which wares are moved on a wheeled cart. Smaller scale car kilns are occasionally used by schools or potteries.
  • Front-Loading Kilns: Front-loading kilns, or side-loading kilns, have a hinged door built into the front of the kiln. Wares are loaded horizontally into the kiln.
  • Top-Loading Kilns: Top-loading kilns have a hinged door built onto the top of the kiln. Wares are lowered down into the kiln, making it easier to ensure they’re centered.

Types of Kilns Based on Material Fired

  • Glass Kilns: Glass kilns are specifically designed to heat glass to very precise temperatures so it can be fused, slumped, or cast.
      • Annealing Kilns: Annealing kilns are used to slowly cool down glass to improve its durability and prevent the glass from experiencing thermal shock.
  • Ceramic Kilns: Ceramic kilns, or pottery kilns, are used to fire pottery, clay, and other ceramic materials.
  • Knife Kilns: Knife kilns, also commonly referred to as heat treat ovens, are designed to heat treat blades to increase their hardness, improve their durability, or otherwise alter their physical properties.
A ceramic kiln is a type of a kiln used for firing pottery and ceramics.
Ceramic kilns are usually more tall and cylindrical since pottery can be stacked during firing.

 

Types of Kilns Based on Use-Case

  • Hobby Kilns: Hobby kilns tend to be smaller and less expensive, intended for home or studio use by artists and crafters. Depending on their size and design, hobby kilns can be used for a variety of applications, ranging from firing single quantities of small ceramics and glassware to firing small batches of wares or more large-scale pieces.
  • Industrials Kilns: Industrial kilns are much larger and more powerful, designed to handle large quantities of materials in industrial settings. Designed for production and commercial use, industrial kilns are used to fire larger quantities of materials or for processes that require higher temperatures.
  • Small Kilns: Small kilns are small, transportable kilns, for firing a small quantity of material. They are typically used by hobbyists who work in a home or studio setting and have limited space. Typically ranging between .6 and 6 cubic feet, small kilns can be used for a variety of applications, such as making jewelry and small ceramic pieces to slightly larger wares.
Small kilns are small, transportable kilns, for firing a small quantity of material.
Small kilns range from .6 to 6 cubic feet. The smallest small kilns are better suited for making jewelry, small plates, and other small wares.
  • Large Kilns: Large kilns are large, often permanently installed, kilns that are designed for industrial or commercial use and can handle much larger quantities of materials. Typically larger than 9 cubic feet, large kilns can be used to accommodate a much wider range of applications.

Types of Kilns Based on Control Method

  • Automatic Kilns: Automatic kilns, or digital kilns, use automatic temperature controllers to execute the firing process and control the temperature of the kiln without user input.
  • Manual Kilns: Manual kilns rely completely on user input in order to execute a firing schedule, although they may sometimes utilize a device known as a kiln sitter to power off the kiln when it’s reached a specific temperature.

Traditional Kilns: The Evolution of Wood Burning Kilns 

The first kilns, developed nearly 10,000 years ago, were extremely rudimentary. They consisted of a hole or trench that was dug into the ground and filled with combustible materials. Pottery was stacked within the flames, and the insulation of the earth allowed the pottery to reach high enough temperatures to fire. This technique, known as pit firing, was extremely sporadic and unpredictable, often resulting in shards of broken pottery.

Wood burning kilns and, later, coal burning kilns, remained the standard up until the industrial revolution. However, over the centuries, technology for wood burning kilns continued to evolve, resulting in greater precision and temperature control. Pre-industrial advancements in kiln technology include beehive kilns, climbing kilns, soda kilns, sawdust kilns, bottle kilns, car kilns, and Anagama kilns – all of which leverage changes in elevation, airflow, and distance from the heat source to better regulate kiln temperature.

Comparisons of Modern Kilns 

While a few contemporary artists and specialists still use wood-fired kilns and traditional firing methods, the industrial revolution introduced the modern kiln, which uses gas or electricity to produce heat. Modern kilns come in a variety of configurations for a variety of applications – from large industrial kilns that are big enough to fill a room to tabletop kilns that are about the size of a toaster oven!

Hobby Kilns vs. Industrial Kilns

The first major distinction between types of kilns is whether they are designed for hobby or industrial use. Hobby kilns tend to be smaller and less expensive than industrial kilns (typically ranging from $700-$2,000 dollars), intended for home or studio use by artists and crafters. These kilns are often electric and digital, making them easy to use and control.

In contrast, industrial kilns are much larger and more powerful, designed to handle large quantities of materials in industrial settings. Industrial kilns can cost tens of thousands or even hundreds of thousands of dollars! Industrial kilns can be electric or gas-powered and may have more complex controls. These kilns play a crucial role in many manufacturing processes and are essential for producing a wide range of products that we use every day.

Small Kilns vs. Large Kilns – Is There a Difference in Performance?

Small kilns vs big kilns…it’s all relative, right?! For this case, let’s think of small kilns as being used by hobbyists who work in a home or studio setting and have limited space. These kilns are typically designed to fire a small quantity of materials at a time and can be easily transported. Big kilns, on the other hand, are designed for industrial use and can handle much larger quantities of materials. They are often permanently installed and require a dedicated space.

But to answer your question – yes. Kiln size can affect performance in several ways:

  • Temperature Distribution: Large kilns may have more difficulty maintaining a consistent temperature throughout the entire kiln due to increased heat loss from the larger surface area. This can lead to uneven firing, resulting in variations in color and texture of the fired pieces.
  • Fuel Consumption: Large kilns require more fuel to maintain the desired temperature, which can increase operating costs.
  • Production Capacity: The size of the kiln will determine the maximum size and number of pieces that can be fired at one time, which can impact production capacity.
  • Heat-Up and Cooling Times: Large kilns may take longer to heat up and cool down than a small kiln, which can affect the overall time it takes to complete a firing cycle.
  • Maintenance: Large kilns may require more frequent maintenance and repair than small kilns due to the increased wear and tear on the components.

Overall, the size of the kiln is an important factor to consider when determining the performance of a kiln. The optimal size of the kiln will depend on the specific needs and requirements of the user.

Gas Kilns vs. Electric Kilns

When it comes to modern kilns, another big distinction is the power source.

Gas kilns use natural gas or propane to heat the materials being fired. These kilns are often used by industrial manufacturers who need to fire large quantities of materials quickly. Gas kilns can reach higher temperatures than electric kilns, making them ideal for certain types of projects.

Electric kilns, on the other hand, use electricity to heat the materials being fired. They are often used by hobbyists and artists who need more control over the firing process. Electric kilns are typically smaller and more affordable than gas kilns, making them a popular choice for home use.

Manual Kilns vs. Digital Kilns

When using a manual kiln, the operator must manually control the temperature and other variables during the firing process, rather than relying on automated controls. This can involve adjusting the fuel source, opening and closing vents, and monitoring the temperature with a thermometer. Manual kilns are often used by artists and craftspeople who prefer a hands-on approach.

Digital kilns, on the other hand, use a programmable digital controller to automatically carry out the firing schedule without direct user input. Modern digital controllers, such as TAP Controllers from SDS Industries, are fine-tuned, intuitive, and provide constant communication and feedback to users. The controllers allow for precise temperature control and can be programmed to follow specific firing schedules.

Differences between Glass Kilns, Ceramic Kilns, and Knife Making Kilns

Different types of kilns are optimized for specific materials. Glass kilns, ceramic kilns, and knife making kilns are made to meet the unique properties of each of these materials and the way they react to heat. Here are some of the main differences in these kiln types:

Temperature Range

  • Glass kilns are typically used for melting and shaping glass at temperatures ranging from 1,1000 to 1,800 degrees Fahrenheit.
  • Ceramic kilns are used for firing ceramics at temperatures ranging from 1,800 to 2,400 degrees Fahrenheit.
  • Knife making kilns are used for heat-treating steel at temperatures ranging from 1,500 to 2,200 degrees Fahrenheit.

Heating Elements

  • Glass kilns often use heating elements made from molybdenum wire.
  • Ceramic kilns often use heating elements made from Kanthal wire.
  • Knife making kilns may use heating elements made from Kanthal or nichrome wire.

Firing Cycles

  • Glass kilns may have longer firing cycles with slow heating and cooling rates.
  • Ceramic kilns may have shorter firing cycles with faster heating and cooling rates.
  • Knife making kilns may have a shorter firing cycle but a longer hold time at the peak temperature to allow for the desired heat treatment of the steel.

Firing Environment

  • Glass kilns often use a controlled atmosphere to prevent oxidation and maintain consistent heating.
  • Ceramic kilns may use a reduction atmosphere to enhance the glaze or surface finish of the fired ceramic.
  • Knife making kilns may have an inert atmosphere to prevent oxidation of the steel.

Size and Shape

  • Glass kilns come in all shapes and sizes, from small, table-top units to large, elongated kilns.
  • Ceramic kilns also come in a variety of shapes and sizes but are typically more cylindrical, since you can stack ceramic during the firing process.
  • Knife making kilns may be smaller and have a long, narrow shape to accommodate blades or other small metal objects.
A 3D rendering of a knife making kiln
Knife making kilns and heat treat ovens are used for making knife blades or for other metal heat treatments.

 

Conclusion

There you have it! Like we mentioned in the beginning, the kiln has undergone many different iterations throughout its history, but hopefully now you have a better understanding of the different types of kilns.

If you’re in the market for a new kiln, we encourage you to check out the kilns available at one of our partners:

And if you’re looking for the most advanced, precise, and easy-to-use automatic kiln controllers to pair with your electric kiln, we invite you to check out the TAP and TAP II Controllers by SDS Industries! With responsive touchscreen controls, an intuitive graphical UI, and integration with the TAP Kiln Controller Mobile App, TAP Kiln Controllers are the most advanced, precise, and easy-to-use automatic kiln controllers on the market today. TAP Controllers can pair with any relay-controlled kiln to help streamline the firing process and give you greater control over your projects.

We invite you to explore our selection of automatic kiln controllers, standalones, and conversion kits on our online store.

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