Evaluation of Color Fastness to Washing: Standards, Test Methods, and Grey Scale Assessment

Color fastness to washing is one of the most frequently evaluated performance properties in textile quality control, measuring how well dyed and printed fabrics retain their color and avoid staining adjacent materials during laundering. This technical guide explains the evaluation principles behind ISO 105-C06, AATCC TM 61, GB/T 3921, and JIS L 0844, covering specimen preparation, test severities, grey scale and instrumental assessment, and typical acceptance criteria. Understanding the full evaluation workflow helps manufacturers, brands, and buyers reduce color-related claims and select the correct test protocol at accredited third-party laboratories.

Technical Overview

Color fastness to washing, also referred to as laundering fastness or wash fastness, quantifies the resistance of textile colors to domestic and commercial laundering. During washing, the combined action of water, detergent, mechanical agitation, and elevated temperature can cause dyes to desorb from the fiber, fade in shade, or migrate and redeposit onto adjacent fabrics. The evaluation therefore has two independent dimensions: the change in color of the specimen itself, and the degree of staining transferred to adjacent materials.

Both aspects are assessed on a grey scale from grade 1 to grade 5, where grade 5 indicates negligible change or staining and grade 1 indicates severe change or staining, with intermediate half-step ratings such as 3-4 permitted. The principal international test methods are ISO 105-C06, AATCC TM 61, the Chinese national standard GB/T 3921, and the Japanese standard JIS L 0844. Results are heavily influenced by:

• Dye class and the strength of the dye-fiber bond (e.g., reactive vs. direct dyes on cotton)
• Dye concentration, with deep shades generally producing lower staining grades
• The completeness of fixation, soaping-off, and rinsing after dyeing or printing
• The selected test severity, including temperature, duration, detergent composition, and mechanical action

Testing Samples

Fabric Specimens

For most routine evaluations, a fabric specimen is cut and stitched face-to-face with a multifiber adjacent fabric of the same dimensions. Under ISO 105-C06 and GB/T 3921, the typical specimen size is 40 mm x 100 mm; under AATCC TM 61 it is generally 50 mm x 100 mm. The composite specimen is then laundered under controlled conditions so that any dye bleeding transfers directly onto the adjacent fibers.

Yarn and Fiber Specimens

Yarns may be evaluated by knitting them into a suitable fabric form, winding them in parallel layers around the multifiber strip, or securing a specified mass of yarn between the multifiber fabric and an inert backing. Loose fibers are combed, laid into a uniform thin sheet, and pressed onto the adjacent fabric. These adaptations ensure consistent contact and reproducible staining results across sample types.

Multifiber Adjacent Fabric

The adjacent fabric is a striped fabric containing six fiber components, commonly wool, acrylic, polyester, nylon, cotton, and acetate (or viscose in some configurations). A wool-containing multifiber (type DW) is used for mild wash conditions, while a wool-free version (type FW) is used for more severe conditions because wool itself is damaged at higher temperatures. Each stripe is assessed separately for staining, which reveals to which fiber types the migrating dye is most attracted. Specimens should be conditioned in a standard atmosphere before assessment, as specified in ISO 139.

Testing Items

The evaluation report normally covers the following items, each expressed as a grey scale grade:

• Color change of the specimen after washing and drying (grey scale for change in color, ISO 105-A02 / AATCC EP 1)
• Staining on each fiber stripe of the multifiber adjacent fabric (grey scale for staining, ISO 105-A03 / AATCC EP 2)
• Self-staining or back-staining observations where relevant, particularly for dark and deep shades
• Any visual irregularities such as crease marks, frosty appearance, or non-uniform color loss

Typical commercial acceptance criteria require a minimum grade 4 for color change and grade 3-4 or above for staining, although individual brand specifications may be stricter for light shades or looser for very dark colors.

Testing Methods

ISO 105-C06 / GB/T 3921

The ISO method uses a rotating wash wheel with sealed stainless-steel containers and a defined liquor ratio. Test severity is designated by a code combining temperature, duration, and the number of stainless-steel balls added to simulate mechanical abrasion. Commonly specified severities include 40 °C for mild hand-wash articles, 50 °C and 60 °C for everyday colored apparel, and 70 °C to 95 °C for severe laundering, with durations of 30 or 45 minutes and 0, 10, or 50 steel balls depending on the selected code. Standard ECE reference detergent is used, with sodium perborate included in certain severe tests to reflect activated oxygen bleach systems. GB/T 3921 is technically aligned with ISO 105-C06, making results broadly comparable.

AATCC TM 61

The AATCC accelerated method uses similar wash-wheel equipment with 1993 AATCC standard reference detergent without optical brighteners. The most widely applied procedure, Test 2A (49 °C, 45 minutes, 10 steel balls), is designed to simulate the color effect of five successive home launderings in a single 45-minute run. Other severities include Test 1A for mild conditions, Test 3A and 4A at 71 °C with increasing mechanical action, and Test 5A, which incorporates chlorine bleach to evaluate bleach sensitivity. ISO and AATCC methods are not directly interchangeable due to differences in detergent, temperature, and machine geometry, so the specification must state which standard applies.

Post-Wash Handling and Drying

After the wash cycle, composite specimens are rinsed, squeezed or blotted to remove excess liquor, and separated before drying in air or a low-temperature oven, typically not exceeding 60 °C. Specimens are then conditioned in the standard atmosphere before grading, because residual moisture and creases can distort visual assessment.

Visual and Instrumental Assessment

Visual grading is performed by trained assessors in a color-matching booth under standardized illumination, comparing the tested specimen against the retained original using the grey scales. Instrumental measurement with a spectrophotometer offers improved objectivity and repeatability: ISO 105-A05 and ISO 105-A04 describe the calculation of grey scale grades from colorimetric data for color change and staining respectively, while AATCC EP 7 provides the corresponding instrumental procedure. In cases of dispute, instrumental results are often preferred because they eliminate observer variability.

Applications

Wash fastness evaluation is applied throughout the textile supply chain, from dye house development to final shipment inspection. Key applications include:

• Incoming and outgoing quality control for dyed and printed fabrics used in apparel, workwear, towels, bedding, and other home textiles
• Dye and auxiliary selection, recipe optimization, and fixation or soaping process validation during product development
• Substantiation of care label claims, such as machine washability at 40 °C or 60 °C
• Verification of compliance with brand performance specifications and product certification requirements
• Root-cause analysis of customer complaints involving shade fading, cross-staining of garments in mixed wash loads, or back-staining of ground fabric in prints

Accredited third-party laboratories routinely perform these tests to support product certifications, buyer approvals, and export documentation, providing results that are recognized across international markets.

FAQ

What does a grey scale grade of 4 mean?

A grade of 4 for color change means the washed specimen shows only slight visible fading compared with the original, while a grade of 4 for staining means only slight color transfer onto the adjacent fabric. Higher grades indicate better fastness, with 5 representing no perceptible change or staining.

Which test severity should be selected?

The severity should match the intended care conditions of the end product. A 40 °C test suits delicate or hand-wash items, 50-60 °C tests suit most everyday apparel, and 70-95 °C or bleach-containing tests apply to heavy-duty or industrial laundering. Buyers' testing protocols usually dictate the exact code, such as ISO 105-C06 or AATCC 2A.

Are ISO 105-C06 and AATCC TM 61 results interchangeable?

No. The two methods differ in reference detergent, temperature set points, liquor conditions, and mechanical action, so a fabric may achieve slightly different grades under each. The applicable standard must be agreed between supplier and buyer before testing.

How many home washes does one laboratory test represent?

AATCC TM 61 Test 2A is calibrated so that one 45-minute cycle approximates five home launderings. ISO 105-C06 tests represent a single laundering cycle at the stated severity rather than a cumulative number of washes.

How can poor wash fastness be improved?

Common corrective actions include selecting dyes with higher fixation and lower substantivity to adjacent fibers, optimizing alkali and salt profiles during dyeing, improving soaping-off with suitable detergents at high temperature, and applying aftertreatment fixing agents. Fixing agents should be validated carefully, as they may reduce light fastness or fastness to perspiration.

Can the assessment be performed with an instrument instead of the grey scale?

Yes. Spectrophotometric assessment per ISO 105-A05 and ISO 105-A04 or AATCC EP 7 converts measured color differences into equivalent grey scale grades and is widely accepted, particularly when visual grades are borderline or disputed.