• Kiln forming is a term used to encompass several types of glass forming which takes place at temperatures between 1,100 and 1,700 degrees Fahrenheit. Also called "warm glass," it doesn't seem merely warm, but glassblowers ordinarily form glass at 2,000 degrees. A kiln is an oven-type device that reaches temperatures high enough to heat the glass for forming.
  
  

Glass Fusing

• Glass fusing involves using a kiln to link pieces of glass. Applying heat softens glass; the more you heat it, the more fluid it becomes. Two or more pieces of glass join when heated. When the right glasses are heated and cooled, the fused glass will be one solid piece. "Fusing" also describes bending and shaping glass. Full fusing, the joining of two pieces by heating until they flow together, requires temperatures of 1,450 to 1,550 degrees F. Tack fusing, which unites the pieces to where they just stick together yet retain individual character, takes place at 1,350 to 1,450 degrees.
  
  

Inclusion

• Fusing can also involve a technique called inclusion, putting ornamental foreign objects into the glass, such as copper, aluminum and brass. The foreign objects can be foil, mesh, wire and metal leaf. If you use inclusion, watch the thickness of the item you're including. Too thick and the glass could break or bubble. Use metal as thin as possible. Be wary of what the metals do under heat, because metal reactions may create effects you want or don't want.
  
  Ornamental air bubbles are also an inclusion technique. One way to achieve it is to mix a thin paste of water and baking soda, spread it on the glass and let it dry. The kiln firing process forms air bubbles of different sizes.
  
  

Glass Slumping

• The most common bending and shaping of glass in kiln-forming is slumping. This involves using a mold to force fused glass into a bowl, plate or other object shape. This happens at 1,200 to 1,300 degrees F.
  
  

Combing and Fire Polishing

• Combing involves using a tool to change the glass shape while hot. This happens at 1,650 to 1,750 degrees. Fire polishing involves using the kiln to heat the glass enough to make the surface shiny. Do this at 1,300 to 1,400 degrees.
  
  

Other Mold Forming

• Some forms of kiln forming use molds to make more complex shapes. Kiln casting melts glass into a mold inside the kiln at 1,500 to 1,600 degrees. Pate de verre forms shapes by heating a "paste of glass" in the kiln at 1,300 to 1,500 degrees. Glass casting involves pouring hot glass into a mold at 1,500 to 1,700 degrees.