What Is Color Fastness Testing and Why Is It Graded Differently for Light?
Color fastness testing measures a textile's resistance to color change (fading) and color transfer (staining) when exposed to the agencies it will meet in service — washing, rubbing, light, perspiration, water, chlorine, and dry cleaning. It is the single most common cause of textile shipment rejection and consumer returns, which is why virtually every buyer technical file specifies minimum grades.
The grading system is the part most often misunderstood. Most color fastness tests use the Grey Scale, rated 1 to 5, where 5 means no visible change and 1 means severe change. Light fastness is the exception — it uses the Blue Wool Scale, rated 1 to 8, where 8 is the highest resistance and 1 is near-total fading. The two scales cannot be compared directly: a "Grade 4" in washing is not the same evidence as a "Grade 4" in light.
Each test produces two independent readings:
- Color change — how much the test specimen itself faded, against the Grey Scale for Color Change (GB/T 250 / ISO 105-A02).
- Staining — how much dye transferred to an adjacent white fabric or multifibre strip, against the Grey Scale for Staining (GB/T 251 / ISO 105-A03).
A fabric can pass on color change and fail on staining (the dye stays put but bleeds onto neighbors), or vice versa. A complete report must carry both numbers for every test invoked.
Which Standards Govern Color Fastness Testing?
Color fastness is governed by three parallel standard systems. They overlap heavily in principle but differ in detail, and a report referencing the wrong system will not satisfy a buyer's specification.
| Standard system | Primary reference | Common market |
|---|---|---|
| ISO 105 series | ISO 105-C06 (washing), -X12 (rubbing), -B02 (light), -E04 (perspiration), -E01 (water), -E03 (chlorinated water) | EU, international |
| GB/T series | GB/T 3921 (washing), GB/T 3920 (rubbing), GB/T 8427 (light), GB/T 3922 (perspiration), GB/T 5713 (water) | China — largely modified adoption of ISO 105 |
| AATCC | AATCC 61 (washing), 8/165 (crocking), 16 (light), 15 (perspiration), 107 (water) | North America |
A point buyers often miss: GB/T 3920-2008 is a modified adoption (MOD) of ISO 105-X12:2001, and GB/T 3920-2024 (effective 2027-01-01) adopts ISO 105-X12:2016. The two are technically equivalent — the friction head geometry, downward force, and stroke are identical. The only changes in the GB version are that normative references are swapped for Chinese equivalents (e.g., GB/T 7565 / GB/T 33729-2017 replaces ISO 105-F09 for the cotton rubbing cloth). A GB/T 3920 result is therefore comparable to an ISO 105-X12 result for the same fabric. ISO and AATCC are not automatically comparable — see the crocking section below.
External references: ISO 105-A02 on the ISO platform and the ASTM / AATCC methods catalog.
What Does China's GB 18401-2010 Mandatorily Require?
This is the question that separates reports written for the Chinese market from those written only for export. GB 18401-2010 ("National General Safety Technical Code for Textile Products") is a mandatory Chinese national standard — not voluntary. Any textile sold in China must comply, and color fastness is one of the controlled properties.
The standard classifies textile products into three safety classes by end use:
| Class | End use | Required color fastness grade (water, perspiration, rubbing — color change & staining) |
|---|---|---|
| Class A | Infants (≤ 36 months) | ≥ Grade 4 |
| Class B | Direct skin contact (underwear, bedsheets, shirts) | ≥ Grade 3 |
| Class C | Non-skin contact (outerwear, curtains) | ≥ Grade 3 |
The same standard also limits free formaldehyde (Class A ≤ 20 mg/kg, B ≤ 75, C ≤ 300) and pH (A/B 4.0–7.5, C 4.0–9.0), and bans cleavable aromatic amines from azo dyes. A fabric that passes a buyer's voluntary color-fastness spec can still fail GB 18401 on the class threshold — an infant garment (Class A) must hit Grade 4 where an adult shirt (Class B) needs only Grade 3. For products destined for the Chinese market, GB 18401 compliance is not optional. Learn more about our GB 18401 textile testing service.
How Is Color Fastness to Washing Tested?
Washing fastness is the baseline test for almost every apparel and home-textile product. The specimen is laundered under controlled temperature, detergent concentration, and mechanical action, together with an adjacent multifibre strip that captures any staining.
- ISO 105-C06 / GB/T 3921 — defines 16 procedures (A1S through E2S). The "S" suffix means a single wash cycle; "M" means multiple (≈5 cycles). Methods A and B run at 40 °C and 50 °C and are the most commonly specified; higher letters run hotter and may add peroxide or chlorine bleach.
- AATCC 61 — five procedures (1A–5A). 1A = hand wash at 40 °C, 2A = machine wash at 49 °C; 4A/5A add sodium hypochlorite.
Typical buyer acceptance: color change Grade 4, staining Grade 3–4. stainless steel balls are added to the wash vessel to simulate mechanical abrasion; the count varies by procedure.
How Is Color Fastness to Rubbing (Crocking) Tested — and Why Do ISO and AATCC Disagree?
Crocking measures dye transfer by friction, separately in dry and wet conditions. Wet crocking is almost always the lower of the two and the more common failure point on dark shades, denim, and heavily dyed jerseys.
The method uses a crockmeter — a weighted finger covered with cotton rubbing cloth strokes the specimen in both warp and weft directions. Staining on the cotton cloth is rated on the Grey Scale for Staining.
Here is the engineering detail most summaries skip:
- ISO 105-X12 / GB/T 3920 specify a rectangular (square) rubbing head.
- AATCC 8 specifies a round rubbing head.
- Comparative studies have found the square head tends to grade about 0.5 grade higher than the round head on the same fabric, because the contact geometry distributes pressure differently.
This is why a fabric can pass ISO 105-X12 at "Grade 4" yet report "Grade 3" under AATCC 8. For a buyer specifying one system, a report issued under the other is not a like-for-like substitute — the test method, not just the grade, has to match.
Typical buyer acceptance: dry crocking Grade 4, wet crocking Grade 3. The cotton rubbing cloth itself is specified by ISO 105-F09 (Chinese equivalent GB/T 33729-2017, a modified adoption of the same).
How Is Color Fastness to Light Tested?
Light fastness measures fading under UV exposure. The specimen is irradiated alongside a Blue Wool Reference (a set of eight standard-dyed wool strips of progressively higher light resistance). When the specimen's fading matches one of the reference strips, that strip's number (1–8) is the grade.
- ISO 105-B02 / GB/T 8427 — uses a xenon arc lamp simulating daylight D65; the specimen and blue wool references are exposed simultaneously, so the grade is read off the reference that faded to the same degree.
- AATCC 16 — also xenon arc, but exposure is measured in AATCC Fading Units (AFU) rather than by blue-wool matching. Typical exposures: apparel 20 AFU, upholstery 40 AFU, drapery 60 AFU.
Typical buyer acceptance: Grade 4 for indoor apparel; Grade 6 or higher for outdoor/automotive/marine textiles, where UV dose is far higher.
Why Does the Multifibre Adjacent Fabric Matter?
For washing, perspiration, and water fastness tests, a strip of multifibre adjacent fabric is sewn or pressed against the specimen to capture staining across a range of fibre types in one shot. The strip contains six bands, each a different fibre, so the lab can see which fibre the dye stains most.
There are two principal types, and they are not interchangeable:
| Band | Multifibre DW (ISO 105-F10) | Multifibre TV |
|---|---|---|
| 1 | Cellulose diacetate | Triacetate |
| 2 | Bleached cotton | Viscose |
| 3 | Polyamide (nylon) | Bleached cotton |
| 4 | Polyester | Polyamide |
| 5 | Acrylic | Polyester |
| 6 | Wool | Acrylic |
DW contains wool and secondary acetate; TV substitutes triacetate and viscose and drops wool. Because wool and acetate are highly receptive to many dye classes, DW is the more demanding and the dominant type used worldwide for ISO 105 and GB/T tests. Using TV where DW is specified — or vice versa — changes the staining readings and can flip a pass into a fail. The standard for the multifibre is ISO 105-F10 / GB/T 7568.7.
What Are the Buyer-Acceptance Thresholds Across All Tests?
Aggregated from typical apparel and home-textile buyer specifications (individual retailers may demand higher):
| Test | Color change | Staining | Notes |
|---|---|---|---|
| Washing | ≥ 4 | ≥ 3–4 | — |
| Dry rubbing | — | ≥ 4 | — |
| Wet rubbing | — | ≥ 3 | Almost always lower than dry |
| Light | ≥ 4 (indoor) / ≥ 6 (outdoor) | — | Blue Wool Scale 1–8 |
| Perspiration (acid/alkali) | ≥ 3–4 | ≥ 3–4 | — |
| Water | ≥ 4 | ≥ 3 | — |
| Chlorinated water (pool) | ≥ 4 | — | ISO 105-E03: 20/50/100 mg/L chlorine |
These are starting points. For China-market goods, the GB 18401 class (A/B/C) imposes its own floor that overrides the buyer spec when it is stricter — infantwear at Class A must hit Grade 4 across the board.
FAQ
What is the difference between ISO 105 and GB/T color fastness standards?
Most GB/T color fastness standards (GB/T 3920, 3921, 3922, 5713, 8427) are modified adoptions of the corresponding ISO 105 methods, and results are technically comparable. The differences are in normative references (Chinese equivalents for rubbing cloth, grey scales) and a few editorial clauses, not in the core procedure.
Is color fastness testing legally required?
In most markets it is not a legal requirement — it is a buyer/contractual specification. The major exception is China, where GB 18401-2010 makes color fastness (and formaldehyde, pH, azo dyes) mandatory for any textile sold domestically, with thresholds graded by product class (A infant / B skin-contact / C non-skin).
Why are light fastness grades on a 1–8 scale when other tests use 1–5?
Light fastness is graded against the Blue Wool Reference — eight strips of progressively higher light resistance — so the scale runs 1–8. Other tests use the Grey Scale (1–5). The two scales measure different things and cannot be compared numerically.
Why does the same fabric pass ISO 105-X12 but fail AATCC 8 on crocking?
The two methods use different rubbing-head geometry — ISO/GB specify a square head, AATCC a round head — and the square head typically grades about half a grade higher. The grade is only meaningful when read against the method actually specified.
What is multifibre DW fabric and when is it used?
Multifibre DW (ISO 105-F10) is a six-band adjacent strip (diacetate / cotton / nylon / polyester / acrylic / wool) sewn against the specimen in washing, perspiration, and water tests to capture cross-fibre staining. DW contains wool and is the dominant type; TV is a non-wool variant and is not a drop-in substitute.
Can color fastness be tested on-site at the factory?
Crocking and basic washing can be approximated on-site with portable kits, but the controlled conditions (temperature, pressure, xenon arc exposure, multifibre staining assessment, grey-scale grading) require an accredited laboratory. ISO/IEC 17025-accredited reports carry weight that on-site checks do not.
Our Testing Capabilities
Beijing ZKGX Research is an ISO/IEC 17025 accredited third-party testing laboratory providing color fastness verification to ISO 105, AATCC, and GB standards. For textile and apparel clients we routinely deliver:
- Color fastness to rubbing — dry and wet, per ISO 105-X12 / GB/T 3920 / AATCC 8, with square-head crockmeter and ISO 105-F09 cotton cloth.
- Color fastness to washing — per ISO 105-C06 / GB/T 3921 / AATCC 61, across the A1S–E2S procedures and 1A–5A, with multifibre DW adjacent fabric.
- Color fastness to light — xenon arc per ISO 105-B02 / GB/T 8427 / AATCC 16, graded against Blue Wool References 1–8.
- Color fastness to perspiration — acid and alkaline, per ISO 105-E04 / GB/T 3922 / AATCC 15.
- Color fastness to water and chlorinated water — per ISO 105-E01 / GB/T 5713 / AATCC 107 and ISO 105-E03 (20/50/100 mg/L chlorine).
- GB 18401-2010 compliance packages — color fastness, formaldehyde, pH, and azo-dye screening by product class (A/B/C) for China-market textiles.
- Grey Scale and instrumental grading — visual grading per GB/T 250 & GB/T 251, with spectrophotometric backing where required.
Acceptable sample types include woven and knitted fabrics, dyed and printed textiles, garments, home textiles, swimwear, denim, upholstery, and children's textile products. To discuss a specific standard, product class, or buyer specification, contact our laboratory.
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Textile color fastness test specimens graded against grey scale and blue wool reference strips in an ISO/IEC 17025 testing laboratory — Beijing ZKGX Research