Birch Studio United States: Longline Sports Bra Built on Recycled Polyester/Spandex 2x2 Rib Knit
Birch Studio, based in United States, needed a longline sports bra that delivered modest compression and support without moving away from a clean, commercial silhouette. The finished fabric was Recycled Polyester/Spandex 2x2 Rib Knit.
Project brief and fabric selection
The fabric selected combines 2x2 Rib Knit (paired rib structure) with rPET from bottles with elastane, giving GRS traceable recycled content. Construction is paired rib structure at 240-300 GSM. The brief also asked for plus shape retention. Each lot was checked against in-house pressure mapping before cutting began.
Construction and fit decisions
Pattern and construction were adjusted around the chosen fabric: seam placement moved away from high-friction areas, stitch density was matched to the elastane content, and the fit block was revised once the first wear trial showed the panel tension distribution. The development brief set the outcome as pressure stayed between 12 and 18 mmHg.
Dyeing and finishing approach
Finishing was limited to processes that support modest compression and support. Soft handle came from construction rather than heavy softening, which keeps performance stable through repeated washing. Consistency between repeat lots mattered more to Birch Studio than an isolated best result.
Measured results
Measured outcome: pressure stayed between 12 and 18 mmHg, verified by in-house pressure mapping. Size sets were checked after five home washes to confirm that dimensional change stayed inside the agreed tolerance before bulk release. Fabric Recycled Polyester/Spandex 2x2 Rib Knit supplied the base behaviour for modest compression and support.
Repeat order performance
The style moved to repeat orders after two seasons. Bulk fabric is now booked against a fixed recipe, with test reports issued per lot, and the 2x2 Rib Knit construction is used for additional colourways in the same programme. The United States market requires documentation, so reports shipped with every lot.
