THE KILN
In pottery, the most important tool of all is the kiln. A kiln uses heat to transform soft, malleable clay into a permanent rock-like state. There are many types of kilns; some use combustion for heat – such as gas, oil, or wood – and others use electricity for a clean source of heat.
FUEL-BURNING KILNS
Fuel-burning kilns include kilns that burn gas, oil, and wood.These types of kilns are commonly used by professional potters, colleges, and art centers because of their large capacity and firing results created. They are also cheaper to operate than electric kilns.
Fuel-burning kilns are typically fired in oxidation and reduction cycles; that is, at certain points during the firing the air is reduced and the gases from the combustion burn in reduction. This starves the flame of oxygen, thus the flame pulls oxygen from the clay and reacts with the base metals that are used as colorants in clay and glazes.
Reduction firing produces specific clay body and glaze color and depth. By pulling the iron to the surface of the clay, the clay color will become a toasty orange color. In reduction, metal colorants such as copper will go from green to red. Rutile will turn from a mustard yellow to a purple blue tint. As you might imagine, the firing results from a fuel burning kiln are tricky to control, and require a fairly extensive knowledge of glaze chemistry and combustion conditions to achieve predictable results.
Because fuel-burning kilns produce combustion gases, they are more difficult to vent than electric kilns. They are usually housed outdoors, such as in a kiln shed or kiln yard.
ELECTRIC KILNS
Almost every ceramic studio has an electric kiln even if it also has a fuel-burning kiln. Electric kilns are far more common than fuel-burning kilns in schools and home studios because they are easier to fire and to vent. These kilns are also smaller and render more predictable results. Electric kilns do not fire in reduction, therefore color and day colors are more uniform.
The heat inside an electric kiln is clean and does not produce combustion gases from the heat source. There are gases emitted during firing, but they are from the clay and glazes as they burn off organic matter and fumes from the metals oxides and carbonates used as colorants in the glazes. These gases are easily vented with a standard setup. Therefore it is far more common to find electric kilns inside buildings than fuel burning kilns.
Even if you plan on building a kiln that fires with gas or wood at some point, having an electric kiln in the studio is a great way to start, use for bisque firing or for testing clays and glazes.
Space and budget limitations generally dictate the choice of a kiln for the home studio, but the most important issue is what types of items will be fired. You might not know exactly what type of projects you’ll be making at first, but imagining future projects and scenarios will help determine the best kiln size. Kilns have specific interior dimensions that will dictate the scale of work you are able to make. Once the ideal size is determined, look at ceramic catalogs and find out what the electrical requirements are for the size kiln being considered. Also, consider the kiln’s exterior dimensions and where it will likely be placed.
If you plan on working small or have limited electrical supply, you can buy a small electric kiln that will plug into a regular household electrical outlet. This might be a good option to begin with because you can always use a small kiln later – after you’ve also purchased a larger kiln – for testing clays, glazes, and application techniques.
Ceramic suppliers provide information about purchasing a kiln; visit their websites. Shop around because prices vary by supplier. Ask potters and pottery teachers for their recommendations. They will have experience with different kilns and can suggest their favorite brands and features.
When you buy your kiln, you’ll also need a venting system. The kiln venting system is some times available from the kiln manufacturer. There are aftermarket vents that work well too.
-Jeff Zamek
Need a Kiln?
Electric: Rocky Mountain Clay offers electric kilns. Just call us and we can get you set up with delivery and installation!
Gas: Cooperworks manufactures the best gas, wood, or specialty kilns in the Denver Metro Area. www.cooperworkskilns.com
Need a Kiln Repaired?
We can repair any issues with a kiln. Just fill out the following contact form or call us with your issue! https://rockymountainclay.com/equipment-repairs/