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All About Kiln Relays

Guide for understanding the difference between different types of kiln relays

No matter what type of kiln or heat treat oven you have, choosing the right kiln relay is super important! Kiln relays play a fundamental role in regulating the temperature of the kiln, as well as ensuring kiln safety. Over the course of this article we’ll be explaining what a kiln relay is, how they work, as well as what type of kiln relay is right for your kiln or oven build.

We’ll also be exploring how TAP Controllers and safety limit controllers like TAP Monitor can help protect you from the consequences of kiln relay failure, so let’s get started!

What Is a Kiln Relay?

Kiln relays are a mechanism that receive signals from the kiln controller and then regulate the amount of electricity sent to the elements of the kiln. Kiln relays rapidly cycle on and off – or “close” and “open.”

When kiln relays cycle on, the circuit closes, and the elements receive electrical current. The kiln element’s electric resistance converts that current into heat, and the kiln gets hotter. When the kiln’s relays cycle off, or opens, it interrupts the current to the elements. This causes the kiln to naturally lose heat.

Kiln relays can open and close extremely fast – ranging from 50 milliseconds for mechanical relays to 20 nanoseconds for solid states relays. This speed, when combined when precise inputs from the kiln controller allows the kiln to execute kiln firing schedules with extreme precision.

Types of Kiln Relays

Not all kiln relays are created equal. They differ by the mechanism they use to open and close the circuit. This mechanism affects their performance, precision, and durability. Kiln relays also differ by their environmental friendliness. For instance, mercury relays are banned in several states and aren’t commonly used for modern kilns, since mercury is highly toxic. Below are explanations of the different types of relays.

Mechanical Relays

Mechanical relays use a physical switch to open and close the relay. That’s why you can hear them click! Mechanical relays are affordable. But since the switch is physical, mechanical relays are more prone to failure. If mechanical relays fail in the open position, your kiln will no longer heat up, which can be a major inconvenience. However, it’s when they fail in the closed position that you have major issues. This causes your kiln to heat up indefinitely – threatening your project and your kiln.

Additionally, since mechanical relays rely on a physical mechanism, they are significantly less precise than other options. And since they have a shorter lifespan, they have a higher environmental cost.

Mercury Relays

Mercury relays use gravity and displacement to open and close the relay. Mercury relays consist of a metal weight in a tube of mercury. Gravity causes the metal weight to fall, displacing the mercury until it closes the circuit. A coil at the top of the tube electromagnetically lifts the weight when it receives current, causing the mercury to recess and open the circuit.

Since mercury relays only use a single moving part, they are extremely reliable – significantly more so than mechanical relays. However, there are some issues with this mechanism. Firstly, it takes time for the displace and recede – so mercury relays have the same level of precision as mechanical relays. Secondly, mercury is highly toxic and exposure to mercury has significant health and environmental risks. These two factors have made mercury relays largely obsolete.

Solid State Relays (SSRs

Solid state relays use semiconductors, electronic parts, and LED or infrared sensors to turn the circuit on and off based on signals from the controller. They do not rely on contact switches or any other moving parts to open or close the circuit. This mechanism has several advantages over other types of kiln relays. First, the lack of moving parts means there is no contact erosion – so solid state relays are extremely reliable and will last pretty much forever, when appropriately rated for the application.

Additionally, the fact that solid state relays rely on electric signals, light, and sensors makes them extremely fast, offering a greater level of precision than any other type of kiln relay. Since solid state relays almost never have to be replaced or thrown away, they are far less taxing on the environment.

What Type of Relay Should You Choose for Your Kiln?

If the summaries above don’t make it obvious, we strongly recommend investing in a solid state relay for your kiln. While they are more expensive than mechanical relays, you’ll end up saving money in the long run by never having to worry about replacement costs. That’s not to mention the potential costs of relay failure, which you exponentially reduce the risk of facing by using an SSR.

Most new kilns have the option for solid-state relays – and your TAP Kiln Controller will be compatible with all three types of relays! If you’ve got an older kiln with mechanical or mercury relays, consider swapping them out for solid-state the next time they need replacement.

How the TAP Ecosystem Helps Protect You from Relay Failure

When we designed TAP, we included all of the quality of life features that we ourselves would want as artists. That included allowing the controller to track usage on kiln components and sending out preventative maintenance alerts, so that artists would be able to replace kiln elements, kiln relays, and thermocouples before they reach the end of their estimated lifespan. All you have to do is enter the life expectancy for your relay(s), elements, and thermocouples provided by your kiln manufacturer or the component’s product sheet!

The TAP Kiln Controller tracks kiln relay usage to provide preventative maintenance alerts to help users replace relays before kiln relay failure occurs.
The TAP Kiln Controller tracks kiln relay usage to provide preventative maintenance alerts to help users replace relays before kiln relay failure occurs.

Additionally, later this year, we’ll be releasing TAP Monitor – the most advanced digital pyrometer and limit controller ever created. TAP Monitor adds the convenience and peace of mind of precise, remote temperature monitoring to your smartphone or tablet. When purchased as a set of configurable components, TAP Monitor can also be wired to a redundant safety relay to act as a safety limit controller, making sure your kiln shuts off safely in case of relay failure.

Explore Kiln Control Solutions by SDS Industries

The TAP Ecosystem includes a host of solutions to enhance kiln safety and help you prevent (or safely respond to) kiln relay failure. In addition to being the most advanced, precise, and easy-to-use programmable digital kiln controllers on the market today, the TAP and TAP II Controllers by SDS Industries provide advanced diagnostics, preventative maintenance alerts, and remote real-time kiln monitoring and error alerts via TAP Kiln Control Mobile App. These features help you prevent and proactively address any potential failures in your kiln or oven build.

Additionally, our soon-to-be released TAP Monitor Digital Pyrometer & Limit Controller can be added to any kiln or oven build, regardless of your current kiln control method, to provide safety redundancy and real-time remote kiln monitoring.

We invite you to explore our selection of programmable kiln controllers, pyrometers, 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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What is an Industrial Kiln? Understanding Commercial Kilns, Furnaces, and Ovens

An in-depth guide to industrial kilns and industrial kiln control

Kilns aren’t just limited to home and studio applications. Industrial kilns, or commercial kilns, are used in a wide variety of industrial processes. From mass producing ceramic tableware to processing plastic, industrial kilns are used to create many of the objects you use in day-to-day life.

Compared to kilns for personal or artistic use, industrial kilns are typically much larger and more powerful, designed to process large quantities of materials in industrial settings. Designed for mass production and commercial use, industrial kilns are often permanently installed and capable of reaching extremely high temperatures.

Example of a front-loading commercial kiln.

Industries That Use Commercial Kilns

Industrial kilns, furnaces, and ovens are used across a wide variety of industrial sectors including:

  • Ceramic: Industrial kilns are used in the ceramic industry to produce tableware, pottery, tile, and other ceramic products.
  • Glass: Industrial glass kilns, furnaces, and annealers are used in the glass industry to produce windows, sheet glass, drinkware, bottles, mirrors, and more.
  • Construction and Building Materials Manufacturing: In the construction industry, commercial kilns and heat treat ovens are used to produce brick, tiles, windows, machinery, tools, and other building materials.
  • Metal Processing and Manufacturing: Industrial heat treat ovens and furnaces are used to process metal for a wide variety of applications including, but not limited to, knifemaking, jewelry production, and silverware manufacturing.
  • Plastic Processing and Manufacturing: The plastic processing and manufacturing industry uses commercial kilns to heat raw material into finished or semi-finished plastic products.
  • Food Industry: In the food industry, industrial kilns and commercial ovens are used to dry, cook, and process food.
  • Waste Management: The waste management industry uses commercial furnaces for incineration, recycling, and energy recovery.

However, these are just a few of the industries that use industrial kilns, furnaces, and ovens. Kilns and ovens are also used in the medical, pharmaceutical, electronic, automotive, military and defense, and aerospace industries (among countless others!).

Read more about the history of industrial kilns.

The Differences Between Industrial Kilns, Furnaces, and Ovens

When it comes to commercial thermal processing equipment, there are three main categories: kilns, furnaces, and ovens. Superficially, all these terms can be used interchangeably. However, typically, each of these terms is used to denote equipment used for specific use-cases or to describe equipment capable of reaching specific temperatures:

  • Industrial Kiln: More likely to be used to describe thermal processing units used to process ceramics or glass. Typically used to describe units that reach maximum temperatures of approximately 1400° C (2552° F).
  • Industrial Furnace: More likely to be used to describe thermal processing units used for metal heat treatment and metallurgy. Often used to describe units that reach peak temperatures exceeding 1400° C (2552° F), all the way up to 1750° C (3182° F).
  • Industrial Oven: More likely to be used to describe thermal processing units used for the food, electronic, medical, and pharmaceutical sectors. Often used to describe units whose processes don’t result in a fundamental phase change (such as drying, moisture reduction, and bakeout).

Industrial Kiln Controllers

Commercial kilns are “industrial grade,” which means they have more stringent requirements for kiln safety and input and output precision. Industrial kiln controllers, also known as ICS (Industrial Control Systems) kiln controllers, must be capable of executing a variety of complex firing schedules with extreme precision.

The TAP Kiln Controller is the most advanced industrial kiln controller, with precise input and output precision.

The TAP Kiln Controller by SDS Industries includes a variety of features and benefits for industrial kiln usage, such as:

  • PID (Proportional Integral Derivative) control algorithms to ensure maximum accuracy between temperature input and output.
  • Multizone temperature control to set specific temperatures in up to three different areas of an industrial kiln or oven.
  • The ability to create, store, edit and execute an infinite number of firing profiles.
  • The ability to remotely monitor commercial kilns and edit and execute firing processes through the TAP Kiln Control Mobile App.
  • Advanced diagnostics and preventative maintenance alerts to ensure peak performance for industrial thermal processes.
  • High quality components for maximum precision and durability.

Read more about the roles and functions of industrial kiln controllers.

Explore Industrial Kiln Controllers by SDS Industries

The TAP and TAP II Controllers by SDS Industries are the most advanced, precise, and easy-to-use industrial 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 to allow you to easily manage and execute your kiln firing schedules.

We invite you to explore our selection of programmable industrial 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 industrial kiln controllers for sale

CTA: Choose the Most Advanced Industrial Kiln Controllers

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A Complete History of Kilns

History of Kilns Blog Header Image

For millennia, humans have been using kilns to fire pottery, ceramic, glass, brick, limestone, grain, metal objects, and other materials. It’s not hyperbole to say that the history of kilns is the history of civilization. Dating back to the rise of agriculture in the Neolithic Age, humans have been using kilns to create the objects they need to support their community – from baking breads and cereals, to creating containers for grain and waters, crafting blades, knives, and tools, and creating fertilizer, mortar, art, and ornamental objects.

Throughout the past 10,000 years, the kiln has undergone many iterations and advancements, resulting in the modern industrial and at home kilns we use today. Today, we’ll be looking at the rich history of kilns from around the globe!

The Early History of the Kilns: 8000 – 6000 BC

The first kilns date back to approximately 8000 BC. Originating in the Near East, early kilns were pit fire kilns – consisting of holes or trenches dug into the earth where wares were placed and then surrounded and covered by wood or other combustible material. While this design was thermally inefficient, unstable, and unpredictable, the insulation from the earth allowed pottery to reach high enough temperatures to fire at least some of the time.

These early pit fire kilns were often temporary structures – and we only know they existed based on the remains of pit fired pottery dating back to this time period. However, the earliest kilns were prone to failed firings and fired pottery was often brittle.

A pit fire kiln.
The pit fire kiln was the earliest iteration of the kiln.

The First Known Kiln: 6000 BC

The earliest known surviving kiln dates back to 6000 BC at the Yarim Tepe site in modern day Iraq. This kiln, which still utilized an earthen firing chamber, represented a major advancement in kiln technology. The kiln was double-chambered, with a clay grate placed over the firing chamber for stacking wares – and its remaining walls suggest that it was dome-shaped at the top to create an updraft and prevent thermal loss (a design also known as a beehive kiln).

In other parts of Mesopotamia, the design of chambered kilns continued to evolve over the next few millennia to be more thermodynamically efficient, allowing for greater volumes of pottery to be fired at higher temperatures.

Early Advancements in Kiln Technology: 3000 – 300 BC

By approximately 3000 – 2500 BC, the ancient Egyptians had begun using vented chambers that allowed wares to be fired while keeping them completely separate from the fuel source. These kilns were built vertically, with an open fire at the bottom that could be stoked to regulate temperature. This design allowed the fire to receive more oxygen while still remaining controlled and thermodynamically efficient.

By the 18th Dynasty (1550 – 1292 BC), the Egyptians had begun firing glazes for pottery and creating early glasswork to imitate precious stones such as turquoise.

An example of ancient Egyptian ceramic glaze.
Ancient Egyptians pioneered the use of glasswork and ceramic glazes.

The ancient Greeks (3000 BC – 300 BC) expanded on the design of Mesopotamian kilns, primarily favoring beehive constructions. Greek kilns were built partially into the earth, with an underground firing chamber. They used clay, and later brick, to construct additional chambers for piling vases and smoke collection.

Ancient Grecian pottery.
Examples of ancient Grecian pottery.

The Rise of Industrial Kilns: 1600 BC – 500 AD

The Romans (625 BC – 476 AD) refined Greek kiln design, adding air flow piping to keep smoke from coloring the fired products, as well as chimneys to improve draft. Improved building materials such as brick and concrete allowed the Romans to build large-scale industrial kilns that were capable of firing up to 40,000 ceramic vessels at a time! The Romans used these industrial kilns to create the clay tile they used throughout their empire.

The remains of an ancient Roman industrial kiln in Morgantina.
The remnants of an ancient Roman industrial kiln in Morgantina, Italy.

The Romans are also attributed with the creation of lime kilns, which they introduced to Britain. Burning limestone was used to create mortar and concrete, allowing for the creation of the famous structures of the Roman Empire. (Later, this technology was used for construction during the Middle Ages – and then to create fertilizer during the 18th century).

In Great Britain, early examples of climbing kilns have been found from during the time of Roman occupation. Climbing kilns (or tunnel kilns) were long, multichambered kilns 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.

Meanwhile, across the world, the Chinese had already perfected the art of climbing kilns. “Dragon kilns” as they were known in China, first began appearing during the Shang Dynasty (1600 – 1046 BC). By the Common Era, “dragon kilns” were widespread throughout China, sometimes reaching up to 60 meters long and capable of consecutively firing 25,000 pieces. Chinese “dragon kilns” were extremely well designed and capable of reaching up to 1400° C in order to fire stoneware and porcelain.

An example of ancient Chinese porcelain (c. 14th- 11th centuries BC)
By c. 1400 – 1100 BC, ancient Chinese kiln technology was advanced enough to fire porcelain.

An Increase in Efficiency and New Techniques: 400 AD – 1700 AD

The Japanese further refined Chinese kiln construction beginning in the 5th Century, creating the famous Anagama and Noborigama kilns. Over the next millennium, Japanese kilns evolved to become extremely thermodynamically efficient. This efficiency allowed the Japanese to later craft the ornate, sophisticated porcelain pieces the country became famous for – the lineage of using traditional techniques in Japan for firing porcelain and ceramics is still alive today!

A climbing kiln in Kyushu Island, Japan
A climbing kiln in Kyushu Island, Japan.

In Europe, throughout the Medieval and Renaissance periods, kilns continued to be an important part of day-to-day life. By the Renaissance, potters had begun using muffle kilns (or reduction kilns) for second or third firings, allowing for the application of additional glazes and majolica. These additional firings allowed for the creation of lusterware, which has iridescent metal glazes and was highly valued during that time period. (However, it’s worth noting that this technique had already been discovered almost 800 years earlier – with lusterware first appearing in modern day Iraq in the early 9th century).

Kilns During the Industrial Revolution: 1700 AD – 1900 AD

As with many industries and manufacturing processes, the Industrial Revolution had a major impact on kiln design. Coal (or anthracite) replaced wood burning and charcoal as the primary fuel source for kilns and ovens. In England, bottle kilns, famous for their bottle-shaped flutes, became commonplace. Despite their inefficiency, bottle kilns were widely used into the mid-20th century.

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.

During this time period, industrial kilns grew in scale – with large factories capable of mass-producing ceramics and other fired goods.

The Rise of the Modern Kilns: 1900 AD – Present

During the Industrial Age, coal-burning kilns were slowly phased out for gas kilns and electric kilns – and the modern kiln was born! Compared to prior kilns, gas kilns and electric kilns were extremely efficient and capable of reaching high temperatures. These new fuel sources and advancements in technology allowed kilns to become extremely big and extremely small – from industrial kilns that are hundreds of yards long to hobby kilns that are about the size of a toaster oven!

Although early modern kilns were all manually controlled, the use of gas and electricity allowed for far more control and precision in regulating kiln temperature, which allowed for more complex firing processes such as those needed for glasswork.

In the 1950s, the kiln sitter was invented, which allowed for kilns to automatically shutoff once they reached a specified temperature.

The Automatic Kiln Controller Revolution: 1986 – Present

The Digital Age brought with it the invention of the automatic kiln controller, which could be programmed in advance to carry out entire firing schedules without user input. While early automatic controllers were complicated and difficult to operate, they still significantly streamlined the firing process.

In 2015, SDS Industries revolutionized the automatic kiln controller industry with the release of the TAP Kiln Controller – the first commercially available consumer kiln controller to utilize an intuitive, graphical user interface. Using touchscreen technology, the TAP Kiln Controller allows users to easily operate their kiln and create, edit and save an unlimited number of firing schedules and steps. Additionally, the TAP Controller allows users to quickly check the status of their kilns with easy-to-read indicators and push notifications to their mobile devices.

User Interface from a TAP Digital Kiln Controller
SDS Industries released the TAP Kiln Controller in 2015.

In 2017, SDS Industries released the first iteration of the TAP Kiln Control Mobile App, which allowed users to remotely monitor and control their kiln from their mobile device – another major leap forward for the kiln control industry. Since then, SDS Industries has continued to be at forefront of kiln control innovation with updates to their mobile app, the release of TAP II Controllers with built-in Wi-Fi integration, as well as the upcoming releases of TAP Monitor, TAP & Go, and TAP Micro.

Enjoy Most Advanced, User-Friendly Automatic Kiln Controllers

The TAP and TAP II Controllers by SDS Industries are the most advanced, precise, and easy-to-use automatic 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.

We invite you to explore our selection of automatic 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

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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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