Fused glass or kiln formed glass is the process of using a programmable glass kiln to partially melt pieces of specially-formulated art glass into a piece of art. Many types of glasses are available but glass fusers often use dichroic, iridescent, transparent, and opaque glasses that have a COE (coefficient of expansion) of 96 or 90. This simply means that the various pieces of glass fused together have to be compatible in their rate of heat expansion and cooling contraction. Otherwise, the resulting fused glass piece can later exhibit stress fractures -- sometimes weeks or months later!

Glass art that I create is hand cut and layered into a design and then kiln fired over a period of about 14-18 hours. Most pieces are comprised of 2-5 layers of glass, which is how the patterns and designs are built up. Often some of my pieces are made up of individual elements that have been created and fired first, then layered together to develop the overall piece of art.  It is then fused together to finish the piece. Temperatures of up to 1500ºF are typical. For a tack fuse, some of the layering and texture effects are preserved by fusing up to about 1400ºF.

During the kiln process, after the glass is “melted” it is held at a temperature that allows all the different layers to unite, in terms of their expansion/contraction, by "soaking" at about 1000ºF. This is called "annealing".  It is important to sufficiently anneal the glass, otherwise stress fractures and inclusions can later appear in the glass.  Sometimes “clean up” of the fused pieces is necessary after initial firings to reshape rough edges or to fix a straight edge.  This is done by grinding the glass to the shape required.  This process however will leave grinder marks on the glass, so it will once again need to be returned to the kiln and fired to a smooth shiny appearance…called fire polishing.  These initial firings all create a “flat” piece.  The item is often then returned to the kiln and fused again (called slumping) into a mold to give it a shape, bowl, curve etc.  Many of my pieces have had multiple firings, sometimes up to 4 or 5 to create the finished product.  This accounts for approximately 60 – 90 hours of kiln firing alone. 

Some of my pieces include the use of dichroic glass.  Dichroic glass was developed over 100 years ago, but has been perfected in recent years by NASA for use as a filter on the windows of the space shuttles. It has the unusual property of reflecting one color when placed against a dark background, while transmitting another when held up to the light. Quite simply, different colors can be viewed in dichroic glass by examining it at different angles.

Dichroic glass is manufactured in an ultra-clean environment, making it one of the most expensive glasses made today. The process involves depositing many very thin layers of rare metal oxides (magnesium, silicon, titanium) on the surface of a piece of glass. A clean sheet of glass -- typically 19" in diameter -- is affixed to a rotating arm within a special vacuum chamber. A container of the designated metal oxides is placed in the chamber. An electron beam vaporizes the oxides, and the resulting particles evenly coat the rotating glass sheet. Dichroic glass is available in a wide range of color combinations, textures, and patterns.