Why activewear is hard on color
Yoga apparel gets an unusual combination of stress. It is washed after almost every wear, it sits against sweat for an hour or more, it rubs against mats, straps and car seats, and it is often dried in the sun or worn outdoors. A fabric that would be fine as a casual t-shirt can lose color quickly as a legging.
The customer does not see "colorfastness". They see a seat that has gone pale, a waistband that has turned a different shade from the leg, or a stain on a light top worn under a dark bra. Each of those problems maps to a specific test, and each test is run on the dyed fabric that will actually go into production.
The four tests buyers ask for most
| Test | Common method | What it simulates | Where it matters most |
|---|---|---|---|
| Colorfastness to laundering | AATCC 61 | Repeated home washing: color change of the fabric and staining of other fabrics | Every style; dark and bright colors in particular |
| Colorfastness to perspiration | AATCC 15 or ISO 105-E04 | Contact with sweat over time | Leggings, bras, hot yoga lines |
| Colorfastness to crocking | AATCC 8 | Rubbing: color transferring to another surface, dry and wet | Dark colors, deep prints, sets worn with light pieces |
| Colorfastness to light | AATCC 16.3 or ISO 105-B02 | Exposure to light, such as sun or a bright shop window | Outdoor practice, display stock, pastels and brights |
Results are usually reported as grades on a gray scale, where a higher grade means less change or less staining. For perspiration, a grade of 3-4 is a common acceptance level. For the other tests, acceptance levels are agreed in the order specification, based on the color, the end use and your own returns history.
Laundering: the baseline test
Washing is the stress every garment sees, so laundering colorfastness is the test to ask for first. The method reports two things: how much the color of the fabric changes, and how much it stains a multi-fiber strip washed alongside it. The second result is the one that predicts a customer's complaint about dye running onto other clothes.
Write the care label after you know the test conditions. If the fabric was approved at a cool wash, the label should say so. A label that allows warmer washing than the fabric was tested at invites failures that the test would have predicted. The labeling rules note covers the care label in more detail.
Perspiration: the activewear-specific test
Sweat is both acidic and alkaline depending on the person and the moment, and both can shift dyes. Perspiration testing exposes the fabric to simulated sweat under pressure and heat, then grades color change and staining. For leggings and bras, this is often the test that separates a fabric suited to activewear from one suited to casual wear.
If your line includes hot yoga wear, treat perspiration results as a gating item for fabric approval rather than a document collected at the end.
Crocking: color that moves by rubbing
Crocking is color transfer by friction. It is tested dry and wet, and the wet result is usually the weaker one. Deep navy, black, burgundy and saturated prints are the usual concerns. In yoga apparel, crocking problems show up when a dark legging is worn with a light top that overlaps the waistband, or when a dark bra is worn under a pale tank.
Light: fading in the sun and on the shop floor
Light fastness matters more than buyers expect. Outdoor classes, beach yoga and garments dried in the sun all expose the fabric to light. So does a display rail near a window. Bright colors and some pastels can shift noticeably. If your line is sold through a studio retail corner with strong lighting, or marketed for outdoor practice, add light fastness to the test list.
Choosing tests by product and color
You do not need every test on every fabric. A practical approach is to group colors and decide which tests apply to each group.
- Dark and saturated solids: laundering, perspiration and crocking, with wet crocking checked carefully.
- Light and pastel solids: laundering and perspiration, plus light fastness if the product is sold for outdoor use.
- Prints: laundering and crocking on the darkest print color, since the print ground can behave differently from the motif.
- Color-blocked styles: laundering with attention to staining, because a dark panel next to a light panel can bleed in the first wash.
Test the dyed lot, not a library swatch
Colorfastness depends on the dye, the dyeing process and the finishing, not only the fiber. A report on a library swatch in a different color tells you little about your custom shade. Ask for testing on the dyed fabric for your colors, and keep the report with the approved color standard. When the fabric is redyed for a reorder, the same question applies again.
Nylon and polyester also take dye differently, which affects which colors are easy to hold. The nylon vs polyester note explains the trade-offs at fabric selection stage.
Where the reports come from
Some mills test their own fabric in house; some send it to an outside lab; some buyers commission their own third-party testing. Each has a place. In-house results are useful for screening, while an independent lab report carries more weight with retail partners. Which reports you need, who pays for them and when they are due should be agreed in writing before bulk fabric is dyed, because a failed test after dyeing means a delay.
We coordinate the testing plan with the mill and the partner factory as part of the quality control process, and we check that the reports match the fabric and colors on your order. If you are starting a line with dark colors, prints or a set, send the desk your color list and the way the garments will be worn, and we will propose a test plan to confirm with the mill.