Have you ever wondered how many different types of kilns are used for pottery? If you have, keep reading.
Here we will look at how kilns are classified, the different types of kilns that have been used throughout time, and answer a few frequently asked questions regarding kilns.
There is a lot of ground to cover, so let’s jump right in.
What is a Ceramic Kiln
A pottery kiln is an insulated chamber of any type that is used to heat ceramic materials to a sufficiently high temperature to cause them to transform from raw clay to a hardened material. To process ceramic materials in this manner is commonly called a firing process.
Kilns can be fueled by wood, gas, or other materials or heated through the use of electric heating elements.
Different Types Of Kilns
Kilns have been in use for almost as long as people have used fire. Over that time, there have been changes to how they are constructed and used.
Here we have listed nineteen different kiln styles that are still used today with some frequency. You may find some overlap between types as many are defined by design features. Others by how they are used, and people use more than one system to classify kilns.
To make understanding these kilns a little easier, we have broken them down into three major groups;
- Modern kilns– These are the designs that are most often used by today’s potters. They are normally gas or electrically fired and use modern methods to monitor and control the kiln.
- Traditional kilns– Traditional kilns operated without the use of modern aids and are still favored by many advanced artisans. They will normally be heated with wood or similar fuels and requires a great deal of skill to maintain a controlled inner temperature in the kiln.
- Primitive kilns– Primitive kilns are the oldest types of kilns. Many are little more than large campfires. The firing methods provided by these kilns are normally reserved for earthenware and stoneware.
If you have a fair amount of knowledge, you may note that we have not classified kilns as Continuous or Periodic as many traditionally would. The reason for this is very simple.
Most people will never likely come into contact with Continuous kilns. These track feed kilns that are designed to operate 24/7 are reserved for industrial use.
Instead, we have limited our list to the Periodic Kilns, often called intermittent kilns, operated by the majority of commercial shops, home potters, and in most teaching environments.
Modern Types Of Kiln
Modern kilns will be the types most often encountered by today’s potters. They offer much more convenience and controllability than older kilns through the use of modern materials and technology.
Most kilns that are considered contemporary or modern will be fueled by gas or powered by electricity. They also have such features as electrical or electronic controls, kiln sitters, and thermocouples to monitor the interior of the kiln and the firing process.
1. Propane Gas Kilns
Propane kilns are one of two types of gas kilns you are likely to encounter. As the name implies, they are fueled by propane burners, much as you would find in a barbeque grill, only on a larger scale.
Burners at the edges of the base of the kiln introduce heat. This can be either on the inside of the firing chamber itself or between the kiln bricks and the outer wall of the kiln in what is termed a bag wall arrangement.
Depending on their size, two advantages offered by propane kilns are their mobility and that they can be used off-grid.
They can be had in either updraft or down draft models and are generally considered harder to control than electric kilns.
2. Natural Gas Kilns
Natural gas kilns are almost exactly like the propane kilns described above and also come in updraft and downdraft models. The one exception is that they use natural gas as fuel for supplying heat to the firing chamber.
This negates the advantages that propane has since, in the majority of locations, natural gas is only supplied by utility companies and is hard piped into the structure of the building.
Natural gas kilns are often favored for industrial or commercial use, where continuous kilns like tunnel kilns and car kilns are utilized. For the majority of potters, though, electric kilns are favored due to the controllability they offer over the firing process.
3. Updraft Kilns
Updraft kilns are gas kilns that have their heating flames arranged at the edge of the firing chamber or behind a bag wall. What makes them distinctive is that the heat travels up the walls of the firing chamber and is then allowed to escape through an opening at the top.
There is an adjustable flue at the bottom of the firing chamber that can be opened or closed to allow more or less air to draft through the chamber.
Thus the name updraft. Air travels from the bottom of the kiln upward through the chamber.
When the damper is closed, it restricts the amount of oxygen within the chamber, which can alter the appearance of the clay or glaze being fired. It also raises the atmospheric pressure in the kiln, forcing heat to be more evenly distributed.
4. Downdraft Kilns
Downdraft kilns are heated in exactly the same way that updraft kilns are. They differ in the fact that their adjustable flue is located at the base of the firing chamber rather than at the top.
This is generally considered a more efficient system and favored by most artists. Like most updraft kilns, downdraft kilns will generally be sprung arch kilns where a slightly arched ceiling will rest upon vertical walls.
However, you will occasionally see a catenary arch kiln that is gas-fired. Natural gas-fired sprung arch downdraft kilns are very popular among more traditional artisans.
5. Oxidation And Reduction
Reduction and Oxidation firing are two sides of the same coin. While technically not specific kiln types, gas kilns can be found that have been optimized for each type of firing. So, in the interest of completeness, we will touch on the subject here.
In a reduction kiln, the amount of oxygen available to sustain the burning of fuel is reduced by restricting the amount of airflow allowed to enter the chamber. Under the condition of “reduced” oxygen, the fire will draw oxygen atoms from glazes such as iron or copper oxide. This chemically alters the glaze and changes its appearance.
Oxidation firing is the opposite of this. Plenty of airflow is supplied to maintain the firing process. An atmosphere rich in oxygen is maintained in the firing chamber of either a downdraft kiln or updraft kiln, and no oxygen is drawn from the clay or glazes.
6. Top Loading Electric Kilns
Modern electric kilns come in two types, front-loading, which we will discuss in the following section, and top-loading kilns. Of the two, top-loading electric kilns dominate the market for ceramic kilns.
As you may have guessed from the name, these kilns are fired not by fuel but through electric resistance coils and aren’t loaded through a door on the front but through an opening in the top.
Top loading electric kilns come in a huge variety of sizes ranging from a very small kiln that is intended for making beads to very large models designed for commercial or educational settings.
See Also: Small Kilns for Home Use
Basic top-loading kilns that rely on peepholes or kiln sitters to help you control the kiln temperature manually can be purchased very reasonably. Nicer models with electronic controls and preprogrammed firing sequences are a little pricier but still within reach of most potters’ budgets.
The one issue some have with top-loading electric kilns is the fact they are top-loading. If you have back issues or are height-challenged, leaning over the chamber walls to load and unload the kiln can be uncomfortable.
7. Front Loading Electric Kilns
The second most popular type of kiln in use today is the front-loading electric kiln. Like top-loaders, they come in many sizes, from stackable countertop models to those that resemble small rooms.
The same control options are available; many front-loading kilns, though are accurate enough to be used in chemical laboratories.
These kilns have doors on the front of them like a cabinet. This makes them much easier to load and unload. The one major drawback to this type of kiln chamber is that they do tend to be pricier than other electric kilns
8. Top Hat Kiln
Our last electric kiln option is the top hat kilns. These are very different than any other kilns you are likely to come across. Instead of your clay works being placed inside the kiln chamber, they are placed on a base called a plinth.
The kiln construction is designed for the chamber to be lowered over the work from above for firing. Once the firing is completed, then the chamber is raised once again to allow easy access to the fired pottery.
In most cases, the raising and lowering of the chamber are achieved through a series of cables and pulleys. You will, however, occasionally see a pneumatic or hydraulic top hat kiln.
9. Microwave-Assisted Firing Kilns
Microwave-assisted kilns are fairly new to the market, and to be honest, the home models are not well suited to ceramics. Limited in size to around 2¾ inches to 6¼ inches in diameter, they are only capable of reaching the neighborhood of 1650 degrees Fahrenheit (900 Celsius).
This is barely in the range for firing clay, and microwave kilns would best be reserved for fusing glass or making very small items from metal clay.
10. Raku Kilns
Raku pottery kilns are designed for a very special process. Making Raku pottery involves removing the pottery from the kiln while it is still red hot and bringing it into contact with combustible materials such as paper or wood in a closed environment.
The resulting flash fire creates a “reduction” atmosphere that, along with the contact between the flames and the pottery, results in the characteristic raku effect.
Opening an electric kiln at these temperatures can shorten the life of the heating elements, so they are rarely USD for raku ceramics. The most common type of raku kiln is a propane kiln.
11. Car Kilns
When most people think of a car kiln, their minds picture one of the large industrial tunnel kilns that are continuous fire and never allowed to cool. There are, however, smaller car kilns that are used in smaller shops and schools.
What makes a car kiln is that the pottery to be fired is loaded on a base called a car and then slid into the chamber. On smaller kilns of this type, the door of the kiln is most often a part of the car and clamped into place after the car has been rolled into place.
Traditional Types Of Kiln
Electric and gas kilns dominate most of the pottery world, but there are still many potteries and artisans that practice traditional techniques and firing methods. In this section, we will look at some of the more traditional styled kilns used by these artisans.
If you have visited some of the historical villages located across the United States, you may have seen some of these in use.
12. Climbing Kilns
The basic premise behind these kilns is heat rises, and it is easier to work with nature than to fight it. They are built up the side of hills and maybe one long open tunnel or a series of interconnected chambers.
Most climbing kilns have historically been wood-fired, but many were also fired with coal. By the same token, they may differ from one to the next by having a single firebox at their base or with several built into them along the sides.
13. Wood Burning Kilns
Wood burning kilns come in a huge variety of shapes and sizes, from a massive bottle kiln to catenary arch kilns and even the wattle and daub kilns many potters build in their backyard.
What they all have in common is being fueled by wood. The most efficient styles seem to be the catenary arch kilns and sprung arch kilns with fire boxes built into one end and a flued chimney stack located on the other to create airflow.
14. Soda Kilns
Soda kilns are used for salt-glazed pottery like stoneware. They are most often of loose brick construction and can be wood or gas-fired.
Soda kilns are usually large enough to walk into and used for firing large amounts of pottery in a single go.
The kiln is loaded, and the opening bricked up. Then the kiln is fired until it reaches a cone nine temperature (2336F /1280C). At this point, either bicarbonate of soda or common salt that has been dissolved in water is sprayed into the kiln.
At these temperatures, the salt or soda is instantly vaporized, and the resulting gas settles over the pottery and reacts with the hot clay to form a glaze. The kiln is then left to cool for several days before being opened.
15. Beehive Kilns
Beehive kilns were large industrial kilns with straight brick walls leading to a high domed ceiling. They got their name from the strong resemblance they bear to traditional European beehives.
The majority of beehive kilns were fired from multiple fireboxes located around the perimeter of the kiln construction. These were separated by the main firing chamber by a bag wall. The heat was forced up to the ceiling, where it was trapped and then drawn back down by a flue located in the center of the floor, creating a downdraft kiln effect.
While there are not many of these kilns still in use, there are still a few being used by companies specializing in classic pottery designs.
16. Bottle Kilns
Bottle kilns were developed later than beehive kilns, and as the name implies, they look much like tall bottles.
Though they appear to be an open chambered kiln with a tall stack from the outside, many actually had baffled inner chambers that created a downdraft kiln effect. Like many large kiln styles of their period, they were constructed mainly of firebrick and fired with coal.
This latter point is created with much of their demise as companies sought to lower the pollution they produced with the environmental regulations that began to appear in the 1970s.
There were two primary types of bottle kilns built; Muffle Kilns and Calcining Kilns. Muffle Kilns were fired at lower temperatures and were used mainly to enamel pottery or apply over glaze detailing.
Calcining Kilns’ main purpose was to fire ingredients that would later be ground for grog and added to other clays to increase their friability and durability.
Our last categories are the most primitive methods of firing clay work that we still use today. In fact, they are probably the oldest methods ever used. They were used to create the earliest earthenware and the vast amounts of artifacts that exist today are testament to what can be achieved even without the use of any modern technology.
17. Stack Firing
Stack firing is the earliest method of firing clay that we know of and has literally been around since the dawn of man.
Clay is formed and allowed to dry the same as we do it today, minus any wheel work. It is widely believed that coiling was the earliest way of working clay.
Once dried, the clay creations were loosely stacked and then surrounded by fuel. In Europe and the Americas, this was most often wood, and in other parts of the world, either wood or coconut husk was used.
Once the full was laid, it was set alight and allowed to burn. Primitive potters learned to determine the temperature of the clay by observing the color of its glow within what amounted to a campfire.
Once the desired heat had been reached, the fire was racked away from the pottery, and the pieces were allowed to cool on their own.
Though this method didn’t involve such a kiln as we think of them today, we fill we would be remiss, not to mention how our ancestors originally created ceramics.
18. Pit Firing
With all likelihood, pit firing probably was a natural progression from the stack method that was discovered by accident.
In this method, a pit is dug in the ground and lined with combustible materials. These could be wood or straw, and there is evidence that dried manure was used in many regions.
Once the pit was lined, the clay objects to be fired were arranged in the pit and surrounded by more combustible materials. Once filled, the entire thing was set ablaze, and the fire was allowed to burn down and die on its own.
In some regions, the pits would often be covered with sand, soil, or other fireproof materials to create what were, in essence, the first reduction kilns.
Once the pit was sufficiently cooled, the fired pottery would be dug out and cleaned. Some artifacts were also carefully polished.
It could be expressed that these early pit firings were the true birth of the kiln.
19. Sawdust Kiln
A sawdust kiln could be thought of as a slightly modernized form of a pit firing. Though in use for eons, this method is still a favorite among weekend warriors who create primitive clay work. They are often built out of common construction bricks, cinder blocks, or even created out of old steel drums.
The basics of how they work are very similar to pit firing. Once a container has been partially constructed, a layer of sawdust or another waste wood material is laid on the bottom.
The clay items to be fired are then arranged loosely on the sawdust, and the space between them is filled with more combustible material. The original layer is then buried in sawdust, and the process is repeated until the kiln or barrel is filled.
Once filled, the kiln is set afire and allowed to burn of its own accord. The clay work is left in place until it has cooled and then dug out for cleaning and polishing.
Frequently Asked Questions
What are the two most common types of kilns?
There are two different answers to the question of what are the two most popular kilns. On one hand, the correct answer would be electric kilns and gas kilns. Electric kilns dominate the market at almost every level but a gas kiln is preferred by many artisans due to it being able to create a reduction atmosphere.
On the other hand, top-loading and front-loading kilns would be the correct answer if you are going by design. Top loading kilns are by far the most commonly seen due in great part to their lower price point.
Front-loading kilns would be second. They are more expensive but much easier to load and unload.
Can you have a kiln at home?
Yes, you can have a kiln in your home. many potters work at home and kilns can be found that range from countertop models all the way up to industrial-sized units. One word of caution. If you are going to install a kiln in your home be sure your wiring can handle its load. It is best to consult a licensed electrician for help.
Can I use my oven as a kiln?
No, you can not use a standard oven as a kiln. 2,759 degrees Fahrenheit(1,515 degrees Celsius) is considered the minimum temperature to properly fire clay. Home ovens are not capable of reaching anywhere near these temperatures.
Can I make my own kiln?
Many home potters build backyard kilns. The majority of these are wood kilns of different designs. They are very inexpensive to build and are a great way to get your feet wet if you are wanting to get into pottery but have a tight budget.
What are the 2 basic types of kiln atmospheres?
The two basic types of atmospheres you can have in a kiln are oxidation and reduction. An oxidative atmosphere is achieved by allowing adequate airflow in the kiln to maintain an oxygen-rich atmosphere. Under these conditions, the oxygen molecules in the clay and/or glazes are left undisturbed.
A reduction atmosphere in a kiln is developed when there isn’t enough fresh air entering the kiln to keep the combustion of the fuel at an optimum level. As the oxygen level drops, oxygen molecules are drawn out of the clay and glazes to help feed the flames.
Reduction firing is most often performed in gas kilns but can wood kilns can also be used if properly outfitted. Electric kilns all operate in an oxidative state.
What is a Tunnel Kiln?
A tunnel kiln is a type of industrial kiln used to fire large amounts of pottery. Instead of pottery being placed into a firing chamber it is loaded onto cars that are carried through a heated tunnel.
These are usually continuous fire kilns that produce pottery on a 24/7 basis.
What is an Intermittent Kiln?
An intermittent kiln is any kiln that is only heated during firing. This category of kiln includes all of the kilns that are normally used by home potters, schools, and small commercial shops.
The name comes from the fact that they are not heated continuously as with continuous kilns but only intermittently as needed.