How swimsuits are made

At one Los Angeles factory, the cloth rests on long tables for days before a worker saws through the stack.

stations: 9
things upstream: 35
raw sources: 11
steps from the ground: 8

The short version

Swim fabric is mostly nylon with 10 to 20 percent spandex, and it gets cut with surprising patience: rolled out, rested for days, then stacked and sawn. Machinists on an assembly line sew one section each. A polyester liner is basted in, and elastic is stretched into the leg and neck openings before a twin needle topstitches it down.

Rest the rolled cloth

Shell fabric arrives as a blend of roughly 80 to 90 percent nylon with 10 to 20 percent spandex, solid or printed. At the Los Angeles factory sewing for the Lime Ricki brand, it is spread on long tables and left for a few days to flatten and relax.

Goes in
Nylon Polyurethane Spandex
Stack and saw

The rested cloth is layered several inches deep, a pattern goes on top, and a worker hand-cuts through the pile with a special saw. Abely, a maker in China, uses a cutting machine for bulk runs instead.
Cut lining and trim

Lining, trim and elastic are cut as separate pieces. Soft lining is usually all polyester.

Goes in
Polyester
Sew the main seams

Machinists join the straps, sides and crotch with a zigzag or stretch stitch, which copes with pulling far better than a straight one. Thread is polyester or woolly nylon, since cotton gives too little and suffers in chlorine and salt water. On an assembly line, each machinist handles one part of the suit.

Goes in
Sewing thread
Baste in the liner

The liner slides in through the neck, and its seams are matched to the suit's at the crotch, sides and straps. A temporary running stitch holds the two together at every opening until the end.
Stretch on the elastic

Elastic goes around the neck and leg openings at about 25 percent stretch. Only the elastic is pulled, and the suit cloth lies relaxed under the needle.
Topstitch the edges

The elastic is folded into the suit and a twin needle runs over it, the last stitching the garment gets. A seam ripper then removes the basting thread.

Goes in
Sewing thread
Inspect each suit

Every finished suit gets its own check, and any that falls short is held back from customers.
Fold and pack

Approved suits are folded and packaged by hand, then shipped to the warehouse.

End of the lineSwimsuit

Worth repeating

Spandex began to be used in swimsuits in the 1960s, almost always blended with nylon.
Spandex is not especially durable, and chlorinated water in pools and hot tubs wears it down faster.
Cotton thread is a poor choice for a swimsuit, because it has too little stretch and holds up badly in chlorinated or salt water.