Color fastness to washing is one of the most critical quality indicators for apparel, quantifying how resistant a garment's color is to fading, bleeding, and cross-staining during laundering. This technical article explains the principles, sampling requirements, test procedures, and evaluation criteria used for washing color fastness determination, with reference to internationally recognized standards such as ISO 105-C06, AATCC 61, and GB/T 3921.
Technical Overview
Color fastness to washing (also called color fastness to laundering or soaping) is the resistance of the color of a dyed or printed textile to the action of washing treatments. During laundering, dyes and pigments may be partially removed from the fabric, resulting in visible fading of the material itself, and the detached color may redeposit onto other surfaces, causing staining of adjacent fabrics or other garments in the same wash load.
Washing fastness testing therefore evaluates two independent properties: the change in color of the test specimen and the degree of staining transferred to one or more adjacent fabrics. Both are rated on a grey scale from 5 (no visible change or staining) to 1 (severe change or staining), and both must typically meet specified minimum grades before an article is released to market.
Poor washing fastness is one of the most frequent causes of consumer complaints and product returns in the apparel industry. It can lead to self-staining between contrast panels of a single garment, cross-contamination of light-colored laundry items, and unacceptable color loss after only a few wash cycles. Retailers, brands, and accredited third-party laboratories consequently treat washing fastness as a mandatory item in routine quality control programs.
Testing Samples
Fabric Samples
For ISO-based methods, a specimen of approximately 100 mm × 40 mm is cut from dyed or printed fabric and attached along one short edge to a multifiber adjacent fabric of the same size. For AATCC methods, the standard specimen size is 100 mm × 50 mm (2 in × 4 in). Printed or yarn-dyed fabrics with repeating patterns should be sampled so that all colors are represented.
Finished Garment Components
Specimens may be cut directly from finished garments, including body panels, pocket linings, collars, cuffs, embroidery threads, sewn labels, and contrast trims. For multi-component garments, the interaction between dark and light areas can be simulated by attaching or sewing contrast sections together to evaluate self-cross-staining under washing conditions.
Yarns and Loose Fibrous Materials
Yarn can be wound onto a suitable frame, knitted into a compact piece, or tied into a skein and bound between adjacent fabrics so that a representative test area is obtained. Loose fibers may be combed and compressed into a pad before testing.
Multifiber Adjacent Fabrics
The staining partner specified in ISO 105-C06 and AATCC 61 is a multifiber adjacent fabric conforming to ISO 105-F10, comprising six dyed-free fiber stripes in a single width (typically including wool, acrylic, polyester, nylon, cotton, and acetate, with a wool-free version available for conditions where wool would be damaged). The multifiber construction allows a single test to reveal which fiber types in a wash load are most susceptible to staining by the specimen.
Testing Items
Washing color fastness programs for apparel typically cover the following assessment items:
- Color fastness to domestic laundering, assessed as color change of the specimen and staining of adjacent fabric.
- Color fastness to commercial and industrial laundering at elevated severity.
- Color fastness to washing in the presence of chlorine bleach or oxygen (non-chlorine) bleach.
- Color fastness to soaping with soap or soap and soda solution, as applied under GB/T 3921.
- Self cross-staining between contrast-colored components of the same garment.
- Verification of care-label claims such as machine washability.
Testing Methods
ISO 105-C06 (Colour Fastness to Domestic and Commercial Laundering)
The combined specimen is treated in a sealed stainless-steel canister rotating in a temperature-controlled water bath using a washing fastness tester. A defined volume of detergent solution (ECE or IEC reference detergent, with or without optical brightener and optional sodium perborate) is added together with a specified number of stainless-steel balls that provide mechanical abrasion. ISO 105-C06 defines a family of test conditions covering temperatures from 40 °C to 95 °C and treatment times of 30 or 45 minutes, with varying ball counts and bleach additions, so that the severity of the test can be matched to the intended care procedure of the article.
AATCC 61 (Colorfastness to Laundering, Home and Commercial: Accelerated)
AATCC 61 uses a similar sealed-cylinder principle with 1993 AATCC Standard Reference Detergent without optical brighteners. The standard defines five accelerated procedures: Test 1A simulates hand washing at 40 °C; Test 2A simulates five home laundering cycles at 49 °C with 50 steel balls; Test 3A operates at 71 °C for higher-severity domestic washing; Test 4A incorporates sodium hypochlorite to simulate chlorine bleach; and Test 5A uses a non-chlorine (activated oxygen) bleach system. Because each accelerated cycle represents multiple actual launderings, Test 2A is one of the most widely specified procedures in buyer protocols.
GB/T 3921 (Colour Fastness to Washing with Soap or Soap and Soda)
The Chinese national standard GB/T 3921 evaluates fastness to soaping using a standard soap solution, or soap plus sodium carbonate in the more severe methods. Numbered test conditions (Method 1 through Method 5) range from mild treatments at 40 °C for 30 minutes to severe treatments at 95 °C for up to 4 hours, allowing mills and garment factories to select conditions appropriate to the fiber type and end use of the product.
Post-Treatment and Drying
After the washing cycle, specimens are rinsed two or three times in cold water, drained, and the specimen is separated from the adjacent fabric except at one stitching line. Both parts are then air dried at a temperature not exceeding 60 °C and conditioned in a standard atmosphere before evaluation.
Evaluation of Results
Color change is assessed against the grey scale for assessing change in color (ISO 105-A02), and staining is assessed against the grey scale for assessing staining (ISO 105-A03). Grades range from 5 (negligible effect) to 1 (severe effect), with intermediate half-step ratings such as 4-5 and 3-4. AATCC procedures use equivalent grey scales together with a chromatic transference scale for staining. Assessment is performed under standardized lighting, typically D65 illumination, by trained observers.
Instrumental Color Measurement
Where greater objectivity and repeatability are required, results may be calculated instrumentally using a spectrophotometer and the CIELAB color difference system, following ISO 105-A05 for change in color and ISO 105-A04 for staining. Instrumental methods are particularly valuable for resolving borderline visual ratings between laboratories.
Applications
Determination of washing color fastness supports a wide range of activities across the textile supply chain:
- Incoming quality control of dyed and printed fabrics at garment factories.
- Validation of dye selection, dyeing recipes, and soaping-off and fixing processes in mills.
- Compliance verification against buyer performance specifications and product labels.
- Support for eco-label and product certification programs that set minimum fastness grades.
- Root-cause analysis of consumer complaints involving fading or staining after laundering.
- Comparative benchmarking of competitive products and new dye or auxiliary chemical developments.
FAQ
What fastness grade is generally required for apparel?
Most brand and retailer specifications require a minimum of grade 3-4 or 4 for both color change and staining to adjacent fabrics, with darker shades and children's products frequently held to grade 4 or higher. The exact acceptance limit depends on the fiber content, shade depth, and the contractual agreement between supplier and buyer.
Why does a well-dyed fabric sometimes show poor washing fastness?
Common causes include incomplete removal of unfixed or hydrolyzed dye after dyeing (insufficient soaping-off), use of a dye class unsuited to the fiber, inadequate fixing treatment, excessive dye loading in deep shades, or poor rinse efficiency. Correcting the after-treatment process often improves the rating by a full grade or more.
Are ISO 105-C06 and AATCC 61 results interchangeable?
No. The two methods use different detergents, temperatures, liquor systems, and abrasion levels, so a grade obtained under one method cannot be directly converted to the other. The method specified in the purchase order or product standard must be followed when reporting results.
How many specimens should be tested?
At least one specimen per color per dye lot is customary for routine control, while disputes, certification testing, or accreditation audits typically require replicate specimens tested in parallel to confirm reproducibility. Sampling should cover all distinct colors, prints, and components of a style.
Can grey scale ratings be replaced by instrument measurement?
Instrumental assessment per ISO 105-A04 and ISO 105-A05 provides objective, repeatable values and is increasingly used to supplement or verify visual ratings, but grey scale grades remain the reference language of commercial specifications in most markets.