The Making of Glass Fiber

Engineered minerals are melted in high-temperature, firebrick lined furnaces, refined to allow volatile materials to escape the “melt.” The melt flows out of the furnace through insulated channels and onto platinum-rhodium bushings. The glass melt is pulled and attenuated through the bushings, then cooled rapidly and coated with a water-based sizing. Each single filament is typically 6 to 32 microns in diameter. There can be 1,000 to 4,000 filaments exiting a typical bushing. In comparison, the average human hair is about 70 microns in diameter. 

Glass Nomenclature


A multi-end roving.

The basic chemistry of the glass is usually referred to by a letter designation, which indicates the preferred application of the particular composition. Table 1, below, lists some common glass types, their applications and associated properties. Two key pieces of information concerning glass fiber properties are specific gravity (used to calculate glass content) and Young’s modulus (used to calculate part stiffness).table-1-reinforcement-types