Art glass is often produced by hand by blowing or pressing. Usually the objects are being formed by remelting already-formed glass and fusing different colors together to form new shapes like marbles, stained glass, glassware, or simply art.
There are four basic styles of art glass furnaces, and they vary widely in design and function. They may be used to melt raw batch, cullet, or both. Some will melt only clear glass, while others will melt colors.
The free-standing pot furnace is the most common furnace type. Many small studios use these furnaces because they are easy to construct, and the crucible is easy to replace if it breaks or wears out. GREENCAST®-94 F PLUS, MIZZOU® CASTABLE, and NARCON® MZA CASTABLE are good options for the free-standing pot furnaces.
Some studios prefer the invested crucible furnace design because the pot is much less prone to thermal shock. The backup material also allows the artist to keep working for a period of time after the pot has broken. GREENCAST®– 94 F PLUS, MIZZOU® CASTABLE, and NARCON® MZA CASTABLE products are good options for the invested crucible furnace design.
The day tank is used to melt and contain the molten glass without the use of a crucible. Usually “charged” (filled with batch or cullet) or “banked” (reduced in temperature, but glass is still molten) at night, the term “day tank” refers to the time that the furnace is actually used to produce glass. These types of furnaces require quality glass-contact materials like ZIRMUL® or KORUNDAL XD®. The superstructure may contain KX-99® or NIKE S65W as an upgrade for improved alkali resistance. The crown/gathering port crown/spacer calls for a material that is high in alkali and creep resistance. An andalusite product, such as VERSAFLOW® 57A PLUS, should work well. High-alumina materials, such as GREENCAST®-94 F PLUS, also have a proven track record in this application.
Continuous-melt furnaces are similar to the day tank, but due to the continuous flow of glass, slightly higher-quality materials are required, such as ZIRMUL® or VISION® in the glass-contact applications and NIKE S65W or VISTA® in the superstructure.
INSWOOL®, INSBOARD, GREENTHERM, and KAST-O-LITE® products are also very important to the construction of all types of furnaces.