Colour Fastness to Perspiration: Testing Activewear Properly
A sports bra spends its working life pressed against skin that is producing warm, slightly salty liquid at a pH that varies from person to person and from day to day. That is a far more aggressive environment than a home laundering test reproduces. When a deep navy bra bleeds onto a light top, or a neon shade dulls in a ring under the bust after two weeks, the cause is almost always perspiration fastness, and it was never tested. This is one of the cheapest tests in the lab and one of the most expensive failures in the field.
The Two Standards and Why pH Matters
The two methods buyers should name are AATCC 15 (colorfastness to perspiration) and ISO 105-E04. Both use artificial perspiration solutions, but they differ: AATCC 15 works at about pH 4.3, while ISO 105-E04 requires two solutions, acidic at pH 5.5 and alkaline at pH 8.0. Human sweat ranges roughly from pH 4.5 to 8, so test both ends. The solutions contain histidine and other amino acids deliberately, because these complex with metals and with metal-complex dyes and cause the shifting that plain water does not.
How to Read the Result
In AATCC 15 the specimen is sandwiched with a multifiber strip in a perspirometer under load and held in an oven at 38 degrees C for 6 hours, then dried. ISO 105-E04 uses 37 degrees C plus or minus 2 for 4 hours under a 5 kg load. Two ratings come back: change in color of the specimen, rated against the AATCC gray scale for color change (EP1) or ISO 105-A02; and staining of each component of the multifiber strip, rated against the gray scale for staining (AATCC EP2 or ISO 105-A03). Workable requirements for activewear are change in color of 4 or better and staining of 3-4 or better on nylon and acetate, rising to 4 for deep shades. Insist that the report shows the actual ratings per fiber, not a single overall pass.
Where Failures Come From
Dye class and shade depth drive almost every result. Acid dyes on nylon give the bright fashion shades buyers want but have weaker wet fastness in deep colors unless properly after-treated with a syntan or fixing agent. Disperse dyes on polyester perform better on perspiration but bring their own risks: sublimation during heat setting, thermal migration into elastane, and poor crocking. Deep shades such as black, navy, wine and dark teal are the ones that fail. Remedies, in order, are a thorough reduction clear, a fixing agent, a slight reduction in shade depth, or a change of dye class. Each remedy costs money and time, so test at the lab-dip stage rather than after bulk dyeing.
Building the Protocol for Repeat Orders
Test every colorway on every fabric lot, and test every component separately: shell, lining, elastic band, printed logo, care label and pad cover fabric. Elastic in particular bleeds badly and is usually skipped. Require both acidic and alkaline results, the numeric gray scale ratings, and a photograph of the multifiber strip. When a shade fails, the fix and the re-test are the supplier cost, not the buyer cost, and that should be stated in the order terms before the first dye lot is run.
Related Fastness Worth Bundling
Perspiration alone is not enough. Bundle it with AATCC 61 test 2A or ISO 105-C06 for laundering, AATCC 8 or ISO 105-X12 for dry and wet crocking at 4 and 3-4 respectively, ISO 105-E01 for water, AATCC 162 or ISO 105-E03 for chlorinated water if the bra is marketed for pool or triathlon use, and ISO 105-B02 or AATCC 16.3 at 20 AFU if the range will sit in lit window displays. A bra can pass perspiration and still ruin a customer white top through wet crocking.
One hour of lab work per colorway at development prevents a category of complaint that no inspection at the factory would ever catch, because the garment looks perfect when it is packed.
