How fiberglass is made

Fiberglass is ordinary glass drawn into threads as fine as silk, then bundled and bonded in resin.

stations: 6
things upstream: 16
raw sources: 10
steps from the ground: 5

The short version

Fiberglass starts as molten glass made from sand, limestone and soda ash. The glass drips through a plate of tiny nozzles called a bushing and is stretched into fine filaments, which are coated with a protective size and gathered into strands. Strands are then woven, chopped or matted and bonded in resin.

Weigh and blend the batch

Silica sand, limestone, soda ash and other minerals are measured by computer and blended. For the reinforcing grade called E-glass, boron compounds are included.

Goes in
Silica sand Limestone Soda ash
Melt it in the furnace

The batch is melted into a glowing liquid in a large furnace. Glass has no true melting point, so it simply softens and flows as it gets hotter.
Feed it to the bushing

Molten glass flows through channels to a small platinum alloy plate pierced with hundreds of nozzles. The bushing is the most important piece of the machine.
Stretch it into filaments

Glass drips from each nozzle and is pulled by a fast-spinning winder into a fine thread. Quick cooling stops it from forming crystals.
Coat it with sizing

A thin chemical coating called a size is applied to the filaments right after they form. It protects them from scratching one another and helps resin bond to them.
Gather, dry and wind

Filaments are collected into strands and wound onto cakes, which are dried. Strands are later woven into cloth, chopped, or laid into mats.

End of the lineFiberglass Next it goes into printed circuit board, wind turbine, surfboard and 9 more.

Worth repeating

In 1893, Edward Drummond Libbey exhibited a dress woven with glass fibers that had the diameter and texture of silk.
Games Slayter of Owens-Illinois invented glass wool for insulation between 1932 and 1933.
The most common glass fiber is E-glass, an alumino-borosilicate glass with less than 1% alkali oxides.