How plastic bottles are made

A soda bottle begins as a clear plastic test tube the size of your finger, which is then inflated to bottle size.

stations: 5
things upstream: 18
raw sources: 8
steps from the ground: 6

The short version

A PET bottle is made in two steps. Dried PET chips are melted and injected into a mold to make a small, thick-walled tube called a preform, with the finished neck already formed. Later the preform is reheated, stretched with a rod and inflated by high-pressure air against a bottle-shaped mold.

Dry the resin

PET chips are dried in hot air, since even a little moisture would degrade the plastic when it melts. The dry chips go straight to the injection machine.

Goes in
PET plastic
Inject the preforms

Melted PET is shot into a cooled mold, forming a clear tube with a closed end. The neck and thread are molded at full size, and they will not change shape later.
Reheat them to softness

Preforms ride through an oven with infrared lamps. They soften until they are rubbery without melting, and the lamps are tuned to heat the walls evenly.
Stretch and blow

A rod pushes the soft preform lengthwise as high-pressure air balloons it into a bottle-shaped mold. Stretching in both directions lines up the molecules and strengthens the walls.
Test every bottle

Cameras and sensors check wall thickness, clarity and neck dimensions. Bottles that fail go back to be recycled.

End of the linePlastic bottle Next it goes into shampoo, sunscreen, aspirin and 12 more.

Worth repeating

Plastic bottles were first used commercially in 1947 but remained impractical until the 1970s, when the PET bottle was introduced.
The 28 mm PET bottle neck finish used for almost all PET beverage bottles worldwide was standardized as PCO 1881, with the guideline finalized in 2009.
PET gives very good barrier properties against alcohol and essential oils, along with a high degree of impact resistance.