By definition, glass fusing is the method used to combine glass pieces by partially melting the glass at very high temperatures. It’s the heat bonding of individual pieces of glass commonly performed in a kiln. Fusing can be done to create stunning works such as jewelry, sculptures, and tableware.
A kiln is an oven or furnace. Typically a kiln is used for baking and drying in pottery, but it’s also a necessity in glassblowing. A kiln is used for slowly cooling—annealing—hot glass after it’s taken its form.
Instead of soldering the pieces of glass together, the glass is overlapped on each other and fired in the kiln with temperatures ranging from 750-850 degrees Celsius.
Fusing cannot be done between glass pieces with different viscosities, as it will cause the glass crack once it’s cooled down. The glass pieces must have the same coefficient of expansion to prevent breakage. Glassblowers tend to stick to using the same brand of glass to ensure proper fusion and compatibility between the pieces.
Other tools such as running, grozing, and breaking pliers are essential glass cutting tools. Running pliers apply pressure to the areas of scored glass so that it breaks evenly. Grozing pliers come in handy for chipping away any excess glass before you start fusing. Finally breaking pliers break the glass along the scored lines you’ve created. Like in ceramics, you have to score—or put lines in—the glass to create a stronger fusion, which is why these pliers are a necessity.
In glass fusion, molds can be used through a process called slumping, which is glass shaped over a mold in high temperatures. The Romans used slumping when creating open vessels like plates and bowls. These molds determine what the shape of your glass will be after it’s fired in the kiln. You can purchase premade molds or make your own at home, but make sure they can withstand temperatures of 927 degrees Celsius.
Glass fusion allows the artist to bend and shape glass into different forms to create beautiful pieces.