How asphalt shingles are made

The crushed stone on a shingle is there to block sunlight, since UV light would eat the asphalt below.

stations: 5
things upstream: 41
raw sources: 14
steps from the ground: 8

The short version

An asphalt shingle is built on a base mat, today usually of glass fiber. The mat is coated with asphalt that contains mineral filler to make it waterproof, and crushed stone granules are pressed into the top surface. A sealant strip on the underside bonds each shingle to the one below it.

Form the glass mat

Wet, random-laid glass fibers are bonded with resin into a thin mat. This base gives the shingle its strength and holds the asphalt.

Goes in
Fiberglass
Coat it with filled asphalt

The mat is run through hot asphalt that has mineral filler stirred into it. The coating makes the shingle waterproof.

Goes in
Asphalt Limestone
Press in the granules

Crushed stone or ceramic granules are pressed into the hot surface. They block ultraviolet light that would degrade the asphalt, protect it from damage and provide the color.

Goes in
Gravel and crushed stone
Stripe on the sealant

A strip of adhesive is put on the back of the shingle. In the sun, it softens and sticks the shingle down to the layer beneath.

Goes in
Adhesive
Cool and cut

The continuous sheet is cooled, cut into shingle shapes and stacked into bundles.

End of the lineAsphalt shingle

Worth repeating

Asphalt shingles are an American invention by Henry Reynolds of Grand Rapids, Michigan, first used in 1903.
Fiberglass shingles overtook organic felt shingles in use by 1982.