What is kiln formed glass, also known as fused glass?

When glass is heated above 1200˚ it becomes as soft as taffy. With more heat glass softens to a honey-like consistency as parts liquefy and fuse together into a singular form.

 

Fusing is, at its most basic, stacking two or more layers of glass in a kiln and heating the glass until it is blended or joined into a single unit. It is then cooled down through an annealing process.

 

Different effects or levels of fusing are achieved by adjusting the temperature and length of time the glass is in the kiln. However in order to fuse successfully, the glass pieces must be compatible with one another, meaning the glass will expand and contract at the same rate when it is heated and cooled. This is known as the co-efficient of expansion (COE). I use compatible glass from Bullseye Glass company.

 

The glass is heated up to 1490˚ F for a full fuse where all the layers melt together as one, or 1375˚ for a tack fuse, where the different layers remain distinct. This creates nice dimension. Next, the glass may be put back into the kiln again for a second time to “slump”. Slumping refers to the glass softening and taking on the shape of a mold such as a plate or bowl. The temperature for slumping is 1225˚ F.

 

Some of the complex detailing on my pieces can look like painting. There's no painting involved, however I do use glass that is crushed to a fine powder for some of the detailing. This powder is called Frit.

 

Many of my pieces use dichroic glass. Dichroic is a special coating placed on glass by using a highly technical vacuum deposition process, originally produced for the aerospace industry.

 

The main characteristic of dichroic glass is that it has a transmitted color and a completely different reflective color. These two colors shift and blend depending on your angle of view and the play of light.

  • Stringer—A spaghetti-like glass shape used as a decorative element in the hot glass arts.

 

  • Frit—Ground glass, ranging in particle size from gravel-like to a fine powder. Frit is sometimes used as a raw material in glass manufacture, and sometimes as a coloring agent or for decorative effect in hot glass crafts like blowing and fusing.

  • Streaky—a glass that is made by mixing two or more molten colors that are swirled in a sheet.

 

  • Dichroic—(pronounced dye-crow-ick) glass, commonly called dichro for short, literally means ”two colored” and is derived from the Greek words ”di” for two, and ”chroma” for color. It was thus named because of its fantastic multi-colored and reflective properties. When you look at this glass, it appears to have more than one color at the same time, especially when viewed at different angles.