Shrinkage and Fabric Growth Solutions for Swimwear: A Technical Guide
This guide sets out how shrinkage and fabric growth can be engineered into swimwear before bulk production begins.
How the problem appears in production
dimensions change after washing or hanging is most obvious the fabric stays wet, stretched and chemically exposed for hours. Buyers usually find it during fitting rather than in the lab, so early target setting matters. Because the fabric stays wet, stretched and chemically exposed for hours, target checks are made on a worn sample rather than flat fabric alone.
Specification targets that work
Set the measurable target at under 3% in length and 4% in width after five washes. Without a number on the tech pack the mill chooses its own standard, which rarely matches the brand requirement. Keep AATCC 135 dimensional change named in the tech pack so every lot is measured the same way.
Fabric and finish options
The practical route combines set the fabric 2% above target width and test relaxation, run a controlled pre-shrink cycle and fix drying temperature by fabric thickness. Options can be combined, but every added step needs extra approval time. Where swimwear is worn for pool training and beach use, set tolerances around that range of movement.
Construction details
Pattern and seam placement decide whether the fix survives wear. Because the swimwear is used for pool training and beach use, allow for worst-case load rather than average use. Any change to nylon and polyester knits at 190-230 GSM with high elastane requires re-testing against under 3% in length and 4% in width after five washes before bulk is released.
Validation before bulk
Approve against AATCC 135 dimensional change and keep reports with the bulk file. A short pre-production run of 30-50 pieces exposes problems a lab sample cannot. Past reports from AATCC 135 dimensional change help the mill reproduce the same recipe on the next order.
