The term "fused glass" refers to glass that has been heated, or fired, in a kiln. Kiln formed glass is another commonly used term to describe fused glass. Different techniques are used to acquire different shapes, forms and textures. Each technique requires different firing schedules in the kiln. Common temperatures range from 1,200 to 1,500 degrees Fahrenheit. Higher temps (1,460 to 1,500 degrees = full fuse) are used to achieve melting of this glass. What goes into the kiln is very sharp with precisely angled corners. What comes out is very smooth with rounded edges and corners. Slightly lower temps (1,325 to 1,380) are used for tack fusing. These temps will allow the glass to keep its basic shape but will soften the edges slightly. Finally, molds can be placed in the kiln with a piece of glass that has previously been full fused. Taking the kiln to a temperature of about 1,225 will allow the glass to "slump" into the mold so it takes the shape of the mold. This is how many bowls, plates and dishes are created.
Each kiln schedule involves a series of "ramps" and soaks." This refers to how quickly you ramp up to specific temperatures and how long you hold, or soak, the glass. These portions of the schedule are extremely important and should not be ignored. A normal full fuse schedule takes approximately 21 to 24 hours to complete.