Wanda Kehlenbeck Tyner - Glass Artist

What is Kiln-forming?

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What is Kiln-forming?

The glass artwork on this website are made using a process called kiln-forming or glass fusing.  This process may be referred to as working with “warm” glass, because the working temperatures of kiln-formed glass lies midway between the extremes of glass blowing (“hot” glass) and stained glass (“cold” glass).

Fused glass is the process of cutting special type of colored glass and using a high-temperature kiln to fuse or melt the glass pieces so that they blend together. This is done to create fascinating color combinations on the surface of the glass and attention-grabbing shapes that would not otherwise be possible. At fusing temperatures, a piece of glass that is placed on top of another piece of glass will soften and melt into the base glass, but the color on each piece of glass stays unique in its color.

Before fusing, the artist will have separate pieces of colored glass cut into various sizes and shapes, but after fusing the artist has a single piece of glass that contains two or more colors with the shapes melted together in an unlimited amount of design possibilities.

Artists who fuse glass can increase or decrease the temperature of the kiln to affect how the glass will melt. At 1500 degrees (the full fusing stage of the heating cycle), two or more pieces of glass will soften and melt completely into each other on a flat kiln shelf, but the base glass will not lose its overall shape. At 1350 degrees, the pieces of glass will not fuse fully, but instead, the upper piece of glass will only begin to sink into the base glass, leaving a raised shape on top of a smooth glassy surface. After glass is fused, it must be gradually cooled so that it does not shatter. This is called the annealing stage.

Once glass is fused together and cooled to room temperature, artists can continue to manipulate the overall shape of the final piece. By placing the glass back into the kiln and heating it slowly to approximately 1250 degrees Fahrenheit, the colorful piece of fused glass can be set on top of slumping molds. The flat glass can be slowly softened into bowls, platters, and various abstract sculptural shapes.

An artist can leave the edges of the fused and slumped pieces in their natural, soft, curved configuration; or they can be shaped and polished outside the kiln with various types of abrasive sanding belts.

The glass for kiln-forming is purchased already colored. The coloring is created at the glass factory by adding various chemicals and elements to the silica mixture that is heated to create the glass. There are four main types of glass used in glass fusing:

  • Opalescent glass – opaque glass that you can’t see through.
  • Cathedral glass – transparent glass.
  • Iridized glass – either opalescent or cathedral glass that has been coated with a metallic coating made of tin. This coating can be silver colored, gold colored, or have a rainbow transition from gold and silver, to purple, blue and green. There are also patterned and textured iridized glasses. Different effects can be obtained depending on whether the iridized coating is facing the bottom of the piece, the top surface of the piece, or is sandwiched between layers of glass.
  • Dichroic glass – Thin layers of metallic oxides, such as titanium, silicon, and magnesium are deposited upon the surface of the glass in a high temperature, vacuum furnace. This creates a brilliant coating on the glass that displays more than one color, especially when viewed from different angles.

The glass is purchased in sheets of varying thickness, crushed glass (frit), powdered glass, thin rods, cane or stringers and thin shards of glass (confetti).

Any glasses fused together have to be tested “compatible” or they will crack upon cooling. Glass has to be heated slowly, and can be brought to specific temperatures to achieve different effects. It then has to be cooled slowly to complete the annealing process. The kilns for glass fusing are usually computer controlled to achieve consistent results. However, in spite of this each hand made glass item will be different, and certain inconsistencies or imperfections are part of the mystery and beauty of this process