How fiberglass insulation is made

Fiberglass insulation is made like cotton candy, with molten glass flung through a spinning cup.

stations: 6
things upstream: 28
raw sources: 8
steps from the ground: 8

The short version

Fiberglass insulation starts as sand and recycled glass melted at about 1,450 °C. The molten glass is forced through the holes of a spinning metal cup, and centrifugal force pulls it into thin fibers. A binder resin glues the fibers into a mat, which is baked at around 200 °C, cut and rolled.

Melt sand and scrap glass

Natural sand and recycled glass are mixed and heated to 1,450 °C to make molten glass.

1,450 °C

Goes in
Silica sand
Fling it through a spinner

Molten glass is forced into a rapidly spinning metal cup with small holes. Centrifugal force pulls the glass out through the holes as fibers, and they cool in the air.
Dab on the binder

A drop of binder goes at each fiber crossing, so the fibers hold together and the mat has cohesion and mechanical strength.

Goes in
Adhesive
Bake the mat

The fiber mat is heated to around 200 °C, which cures the resin binder.

around 200 °C
Press it flat

The mat is calendered, which means it is pressed between rollers, to give it strength and stability.
Cut, roll and pack

The mat is cut into batts or continuous blankets, packed in rolls or panels, and palletized.

End of the lineFiberglass insulation Next it goes into dishwasher.

Worth repeating

Games Slayter discovered mass production of glass strands in 1932 when he blew a jet of compressed air at a stream of molten glass.
Fiberglass insulates because it traps air in tiny pockets, and small gas cells stop heat from carrying by convection.
In 2011, the US National Toxicology Program removed bio-soluble glass wool used in building insulation from its Report on Carcinogens.