You can classify kilns for pottery and ceramics in many different ways. The two most common are their heat source and airflow design, but the atmosphere they create and other factors can also come into play.
This article looks at the most common types of kilns you are likely to encounter, discusses their benefits and limitation, and answer a few of the most commonly asked questions related to kilns.
Different Types of Kilns for Ceramics and Pottery
Kilns are used for various purposes, from making bricks to fine china. While all operate on the principle of heating material to very high heat in order to transform the materials in them, they vary significantly in design.
Here we will look at the most common types of pottery and ceramic kilns used today.
1. Electric Kilns
By far, Electric kilns are the most popular type used today. They were initially designed for small-scale production, as found in most schools and craft centers.
Because they offer a high degree of controllability, artisans, commercial, and many industrial users have now moved to their use. Another plus for electric kilns is their reliability. In commercial and industrial use, you cannot overemphasize this point.
Because electric kilns don’t require the combustion of fuels, they generally have an oxygen-rich atmosphere. However, you can achieve a reduction atmosphere with specific techniques.
You can find many small electric kilns available today suitable for hobbyist use.
2. Gas Fired Kilns
Gas-fired kilns were once the favorite type of kiln, especially among artisans. Electrics have overtaken them, but rising energy prices are seeing them make a resurgence.
Gas kilns come in many different designs depending on how they open, draft, and the atmosphere produced. They can use LPG, propane, butane, and even methane gases as fuel sources. By far, propane and LPG are the most common.
Natural gas and propane gas kilns are most familiar, with both updraft and downdraft models being popular.
Updraft kilns generally have burners on each side. The flames travel up each side of the chamber to provide even heating. Inside many gas kilns, you will find a bag wall. Bag walls are loose assemblies of material, most commonly fire bricks, that shilled the pottery from direct contact with the flames.
The flames travel up the outsides of the chamber, and hot gases, exit out the top. Thus their name.
Downdraft kilns differ from updrafts in that the waste gases exit through the bottom of the kiln before entering an exhaust flume. The circular flow pattern provides more efficient heating.
Whether you want an oxidation or reduction atmosphere, you can find a gas kiln to meet your needs.
4. Kilns That Use Other Fuels
Gas and electric kilns are relatively new kids on the block. Before their advent, most kilns used wood, charcoal, or coal as a heat source. While these are fairly rare to find today, many traditional craftsmen still favor them. The grain and finish these traditional kilns provide are very different from what modern kilns provide and allow the artisan to have greater control over their finished products.
A major drawback is that they are much harder to control and require specialized skills to deliver quality results.
Anagama kilns are the most famous of these traditional kilns. Wood fired, these kilns have been in use in Japan since the 5th century and are still thought to produce the finest pottery and ceramics.
5. Intermittent kilns
We are most familiar with intermittent kilns. The kiln is loaded and sealed, then brought up to temperature. You then start the firing process. Time and temperature follow a preselected process inside the kiln.
After firing, you allow the entire kiln and the ceramics or pottery inside to cool.
6. Continuous kilns (sometimes called Tunnel kilns)
People producing large amounts of ceramics and pottery often use a tunnel or continuous kiln. Driven by conveyor belts, the material you want to fire is slowly fed through a large box. The center of the box is normally the hottest point. The kiln gradually brings the pottery up to temp as the belt travels towards the hot spot, it is then fired, and then cooled as it moves to the excite of the kiln.
Continuous kilns may be electric or gas but many wood and coal-fired models are still in use.
7. Chamber Kilns
Chamber kilns are a subtype of the intermittent kiln. They come in two varieties front-loaded and top-loaded. This, obviously depends on where their door is located.
A Chamber kiln consists of a sealable thermal chamber where pottery and ceramics are placed for firing and then sealed. Most modern chamber kilns are equipt with electronic controls making them very easy to manage even for novices.
8. Bell or Top-Hat Kilns
Tophat kilns have a stationary firing surface. You place the wares to be fired on the hearth and then the chamber or top hat is lowered over them.
You will see bell kilns with virtually any common heat source including gas, wood, and electricity. A top-hat kiln’s size is limited by the lifting apparatus that can be fitted in the studio.
9. Raku Kiln
Rakuware is a traditional form of Japanese pottery normally used in tea ceremonies. A Raku kiln is the special low-temperature kiln used to produce this rather porous type of pottery.
Raku kilns come in many different shapes and use a variety of heat sources. Their main characteristics are they are designed to come up to temperature very quickly and to allow the easy removal of the rakuware while at maximum temperature.
10. Roller-Hearth Kiln
Roller-hearth kilns are most commonly used in the manufacture of earthenware and ceramic flooring tiles. The items to be fired are placed on bats which are then drawn through the continuous kiln riding on rollers.
While you will rarely see them outside of industrial settings, you will occasionally see one in a craft school.
11. Anagama Kiln
Anagama kilns are some of the oldest kilns still in use. They have been a mainstay of Japanese potters since the 5th century. Consisting of a long, narrow chamber with a firebox at one end and a flue at the other.
Operating at relatively low temperatures compared to modern kilns, fire times in Anagama kilns can last from one day for fine pieces to two weeks for larger works of pottery.
What is a periodic kiln used for?
Periodic kilns are the type that most people are familiar with. Periodic kilns get their name because they are not firing on a continuous basis. You load the kiln, seal it, bring it to temperature, allow it to cool, and empty it when done.
Hobbyists, schools, small industrial producers, commercial pottery, and ceramic shops mostly use periodic kilns to produce small batches of wares.
What are the advantages of a periodic kiln?
Periodic kilns offer several advantages. The sealed chamber lets you control the atmosphere inside. They are very versatile allowing for the firing of many different sized works and works of different materials. Modern periodic kilns mostly have electronic controls giving you very precise control over firing conditions and times.