Kilns: Overview And Use With Ceramic Clay

If you’re working with ceramic clay, you’ll need to have access to a kiln in order to finish your work.

Kiln Overview

A kiln is essentially a very high temperature “oven” of sorts that can reach temperatures over 2,000* F. Different types of clay fire at different temperatures, so if you work with ceramic clay, be aware of which kind you are using. A “low-fire” clay (one that requires a low temperature in the kiln) will melt if fired at too high a temperature. Conversely, if you’re using a “high-fire” clay (one that requires a high temperature in the kiln) and fire it to too low a degree, it will never be completely solid (or “vitreous”).

There are many different types of kilns, but today, they are mainly heated either by gas or electricity. Large-scale production companies generally use gas kilns and small-scale production (hobbyists, schools, etc.) typically use electric kilns. They come in a variety of sizes from 8” x 8” x 6” (for very small, individual works) to very large, walk-in kilns. Here is a photo of artist Jun Kaneko working on a large ceramic work inside his kiln:

Jun Kaneko in his Omaha, Nebraska studio/kiln, working on one of his massive dango (“dumpling”) ceramic pieces.

Jun Kaneko in his Omaha, Nebraska studio/kiln, working on one of his massive dango (“dumpling”) ceramic pieces.

The bricks that are surrounding him make up the inside of his kiln. In this photo, Kaneko is adding glaze to his piece. Glaze is like paint, but it is comprised of glass elements, so when it is heated to a high temperature, the glass particles melt and create a hard, glossy surface (think of a coffee mug). Because the glass particles melt, Kaneko has his piece supported by bricks so that if the glaze melts down the bottom of his piece, it doesn’t fuse to the kiln floor. If the glaze melts down onto the bricks, they can be tapped lightly with a hammer to remove them from the ceramic piece.

If you’re interested in buying a kiln, you can get a brand new kiln from between $400 and $4,000, depending on size and type. Many times, you can find used kilns online or in the classified ads for much less. Keep in mind that electric kilns may require a specific type of circuit. While some small jewelry kilns may be able to run off of household 120 volt power outlets, larger kilns will require 220 or 240 V. If you don’t already have this in your home or studio, it can be very costly to have it installed! Do your research before making any decisions.

Kiln Use

Ceramic clays are made from clay minerals and other raw materials. They are water-based, meaning that eventually the water in the clay will evaporate and it will become hard and brittle. To keep them from falling apart, pieces made from ceramic clay must be fired in a kiln.

In ancient times, people mined clay from the earth and made vessels and pottery pieces that were then fired in primitive kilns, kept hot over many hours with fire.

Pieces made from ceramic clay are allowed to air dry for a period until the majority of the water has evaporated, then they are fired (i.e. “baked” but don’t say that to a professional ceramicist!) at high temperatures until the clay becomes solid. Think about the tile in your bathroom or your coffee mug—chances are they are made using this process.

The benefit of using ceramic clay is that, once fired, it can last forever (unless you drop it and break it—same as your coffee mug). The drawback is that, unless you have access to a kiln, ceramic clay will become very brittle and crumble. Ceramic clay also requires a bit of “babysitting.” When you are working with ceramic clay, the piece must be kept damp with a spray bottle of water and wrapped in light plastic in order to keep it pliable. Clay dust is also a health hazard as it contains bits of silica. If you work with ceramic clay, don’t ever sweep dry bits of clay—instead, use a damp sponge to pick up any clay dust. Once the clay has been fired, don’t attempt to sand it for the same reason—silica can be released into the air, and it’s not good to breathe.

Most kilns today are electric and require only that you flip a switch and have patience until your work is ready.


An electric kiln







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