Colour Fastness Requirements for Sports Bra Fabrics
Activewear is the hardest category for colour. A bra is worn next to skin, washed more often than almost anything else in the wardrobe, and exposed to sweat, friction under the arm, sunscreen on the back and shoulders, chlorine in some programmes, and sunlight when training moves outdoors. A fabric that passes a basic wash test can still fail in the field, which is why the fastness spec for this category has to be broader than the one most mills offer by default.
The minimum set to require
Start with six tests and grade them to the ISO 105-A02 grey scale for colour change and ISO 105-A03 for staining. Washing to ISO 105-C06 or AATCC 61 at grade 4 for change and 3 to 4 for staining. Perspiration to ISO 105-E04 or AATCC 15, acid and alkali, at grade 4. Rubbing to ISO 105-X12 or AATCC 8 and AATCC 116, dry at grade 4 and wet at 3 to 4, with grade 3 acceptable on very deep shades. Light to ISO 105-B02 or AATCC 16 at grade 4. Water to ISO 105-E01 at grade 4. And chlorinated water to ISO 105-E03 at grade 4 where the range is sold for pool or multi-sport use.
Why nylon is the risky one
Deep shades on nylon dyed with acid dyes are the most common source of bleeding, especially in red, royal and navy. Two practical fixes: specify nylon 66 rather than nylon 6 where the price allows, because it holds dye better and has a higher melt point, and require a proper fixing and aftertreatment step in the dye recipe rather than a standard rinse. Elastane is the second risk, because spandex takes up disperse dye readily and releases it slowly, which shows up as staining on adjacent panels and on lighter trims. Ask specifically about elastane staining, not only overall fastness.
Sunscreen and other real-world agents
There is no dedicated ISO number for sunscreen staining, so most brands run an in-house spot test: apply a standardised amount of a high SPF formulation to the fabric, hold it under load at elevated temperature for a set period, launder once, then grade the change. It takes half a day and catches a failure mode no standard test will. Do the same for deodorant and antiperspirant on the underband area, where aluminium salts and fragrance oils sit directly against the fabric.
Heat, pressing and bonding
If the construction uses adhesive film on the cut-out edges or heat transfer labels, add ISO 105-P01 colour fastness to dry heat and run a press trial at production temperature and dwell time on the actual shade. Yellowing of white and pale shades after pressing is common with elastane-containing fabrics and is entirely avoidable if it is tested before bulk rather than discovered after packing.
Shade control across the program
Fastness and shade consistency are separate problems. Hold bulk to a delta E of 1.0 or less against the approved standard, view under multiple illuminants in a light box, and require a lab dip and a bulk shade band per lot. Where a cut-out back style combines a shell, a mesh backing and binding, shade all three together, because a mesh that matches in daylight can flare badly under store lighting. Inspect incoming lots for shade variation within a shipment to ANSI/ASQ Z1.4 at AQL 4.0.
Six tests, one in-house spot test and a defined delta E. That is the whole specification, and it prevents most of the colour complaints this category generates.
