How stainless steel water bottles are made

Many steel bottles begin as a straight tube of metal that is inflated with water pressure into a bottle shape.

stations: 7
things upstream: 74
raw sources: 25
steps from the ground: 10

The short version

A stainless steel tube is cut to length and placed in a water expander, where huge pressure swells it into a bottle with no base. Inner and outer bottles are necked, threaded and cleaned, then nested and welded to a bottom plate. Air is pumped from the gap between them, and the bottle is polished, coated and tested.

Cut the steel tube

Raw stainless steel tube is cut to the length needed for the inner or outer bottle.

Goes in
Stainless steel
Inflate with water pressure

The tube is clamped in a water expander and filled with water under enormous pressure. The wall swells outward into a bottle shape, with no bottom yet.
Neck and thread the top

A press forms the shoulder, a machine squeezes the top into a neck, and a threading machine rolls threads for the cap. The edges are then trimmed and smoothed.
Clean the shells

Ultrasonic cleaning removes oil and dust so the surfaces are clean and dry before assembly.
Nest and weld the bottom

The inner bottle is pressed inside the outer one, a round bottom plate is added, and the outer bottle and plate are welded. A water test then checks the welds.
Pump out the gap

The space between inner and outer walls is evacuated. This vacuum stops heat from conducting across and keeps the outside of a hot bottle comfortable to hold.
Polish, coat and test

The outer surface is polished, then powder-coated or painted. Logos are printed, and sample bottles are tested for leaks, insulation and drops.

Goes in
Paint

End of the lineStainless steel water bottle

Worth repeating

A water-expanded steel bottle comes out with no bottom, so a round plate has to be welded on before it can hold anything.
One water expansion tube can yield two outer shells, which are then cut apart.