Difference Between a Glass & Ceramic Kiln

Ceramic kilns are often used for firing glass.

Ceramic and glass kilns are both made from the same materials, but there are distinct differences in how the kilns work. While glass can be fired in a traditional ceramic kiln, there are modifications that need to be taken into consideration.

Energy Source

Ceramic kilns are powered by gas, electricity and wood fire heat. Each of these has its own advantages, but the kilns that are easiest to use and have more versatility are electric. Most glass-specific kilns are electric. Electric ceramic kilns can be modified, with the help of varied shelves and temperature monitoring, to accommodate glass pieces.

Heating

Kilns made specifically for ceramics are heated from the sides in order to heat multiple layers all at once. Glass kilns have heat that comes from the top of kiln, typically in a clamshell lid. Glass kilns heat single layers of glass, keeping the temperature uniform to prevent cracking. Ceramics need to be fired at higher temperatures than glass as well. While glass can be fired in a ceramic kiln, the heat will have to be monitored more closely and the glass will have to be loaded carefully to prevent the pieces from being heated unevenly. A programmable kiln allows the user to set the temperature and fire glass pieces with little fuss, according to a brochure from Skutt Kilns and Wheels.

Size

Ceramic and glass kilns have different shapes and sizes. Ceramic kilns need to heat multiple layers so they are typically tall and narrow, enabling the user to place many different shelves inside. Glass kilns, because the heat comes from above, are long and shallow. Both glass and ceramic kilns can be purchased with different loading capabilities. Some kilns are front loading, while others are top loading with a clamshell lid. Front-loading kilns are good for firing glass that needs to be handled for manipulation during firing, according to "A Beginner's Guide to Kiln-Formed Glass."

Ceramics

Commercial ceramic kilns come in many sizes, from small, microwave-sized kilns to ones big enough to fire 4-foot pieces of pottery. Electric ceramic kilns are lined with fire brick and are usually metal on the exterior. Shelves made from material that can withstand high heats are used to layer pieces in order to fire more pieces at once. The "Potter's Studio Handbook" states that the shelves are very delicate and must be handled with care.

Glass

There are different accessories made specifically for glass kilns. Because of the varying thicknesses of the glass to be fired, the shelves are often made from vermiculite, which leaves a smooth surface on the bottom of the glass and distributes the heat evenly. One negative aspect of vermiculite is how it holds moisture. Moisture in the kiln during firing can cause glass to bubble. Bead collars are available for glass kilns. Collars are stacked inside a glass kiln in order to make beads. Collars do not have heating elements and have small doors where beads can be added and removed.

References

• Skutt Kilns and Wheels: Glass brochure
• "A Beginner's Guide to Kiln-Formed Glass"; Brenda Griffith; 2007
• "Potter's Studio Handbook"; Kristin Muller; 2007
• Big Ceramic Store: Buying a Kiln Tutorial