How bras are made
Many molded bra cups are baked in a hot mold with a removable rib inside, which leaves a hollow tunnel for the wire.
- stations
- 8
- things upstream
- 60
- raw sources
- 16
- steps from the ground
- 8
The short version
A modern molded bra starts with sheets of foam that are pressed between heated, cup-shaped molds until they hold a rounded shape. Stretchy fabric is cut into panels and bonded or sewn around those cups. A curved strip of coated steel slides into a channel under each cup, and a band of elastic, a pair of straps and a row of wire hooks finish it.
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Cut the stretch panels
Stretchy cloth is spread in stacks and cut into cups, wings, center pieces and straps. The cloth is usually nylon or polyester with a small share of spandex, a fiber that can stretch up to five times its own length and spring back.
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Bond foam to the cloth
A thin layer of foam is laid against the inner face of the cut cloth and the two are hot-pressed together. Heat makes the foam tacky, so it grips the fabric with little or no extra glue.
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Press cups in a mold
Two foam layers go into a heated mold with a cup-shaped cavity on each side and a slim forming rib sandwiched between them. The mold closes under heat and pressure, and when it opens the foam keeps its rounded shape. Pulling the rib out leaves an arched tunnel along the bottom of the cup.
180 to 185 degrees in one patented method
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Trim the molded edges
Cutters follow the outline of each pressed cup and clip away the flash around it. What remains is a finished shell with a ready-made channel for the wire.
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Shape and tip the wires
Thin strips of steel, or of nickel titanium, a shape memory alloy, are bent into a U and given a nylon coating at both ends. The soft tips stop the metal from poking through the cloth after months of wear and washing.
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Sew cups to the band
Machinists stitch the cups to the center piece and to the side wings, then run elastic along the bottom band and the edges. The elastic carries most of the lift, and the straps mostly hold things in place.
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Slide in the wires
A wire is pushed into the channel under each cup, running from the center out to the armpit. The open end of the channel is then stitched or capped shut so the wire cannot work its way out.
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Fit hooks and straps
A strip of bent wire hooks goes on one end of the band and a matching strip of eyes on the other. Adjustable straps are sewn on last, and each piece is checked against its size before packing.
Goes in
Worth repeating
- About 500 million bras were sold in the United States in 2001, and roughly 70 percent of them had an underwire.
- Underwire bras are a known cause of false alarms at airport metal detectors.
- Hook-and-eye fasteners were once bent from wire by hand, and Redditch, an English town famous for sewing needles, was the first place to make them by machine.
Back to the ground
Follow every input upstream and bra starts as these 16 raw sources.
Everything it is made of See it on the map
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Keep walking
Sources
- Underwire
- Hook-and-eye closure
- Spandex
- US9603391B1 - Method of forming an underwire channel of a bra
- US7458877 - Bra and method of making it
These sources say little about the factory steps themselves, so parts of this line are a general description. Treat the details with care, and tell us if you know better.
Cite this page: "How bras are made." Assembly Line, 2026-11-03. https://assemblyline.org/make/bra