Whites turning grey, dye bleeding onto shirts, cuffs fading pale — most workwear complaints trace back to one hidden metric: color fastness. It never shows on a quotation, and only reveals itself after washing. This article covers three things: how fastness grades are read, what "Grade 4" actually means, and which 6 test reports to demand at acceptance.
1. How fastness grades are read
Color fastness measures how firmly dye is fixed to the fiber, graded 1–5 against the grey scales in GB/T 250 (color change) and GB/T 251 (staining):
| Grade | Meaning | Buyer's verdict |
|---|---|---|
| 1 | Severe fading / staining | Reject |
| 2 | Obvious fading | Fail |
| 3 | Noticeable fading | Marginal for outerwear |
| 4 | Slight change, visually near-none | Pass line for workwear |
| 5 | No change | Premium, higher cost |
"Grade 4 color fastness" in industry talk means the fabric reached Grade 4 on both grey scales — visually near-identical after washing, with no dye transfer onto lighter garments. For workwear worn daily and washed weekly, Grade 4 is a reasonable floor. Fabric below Grade 3 will almost certainly generate complaints after bulk delivery.
2. Fastness is a family of metrics, not one number
The most common buyer mistake is signing off on a single "Grade 4" claim. Fastness is tested under different conditions, and one fabric can be Grade 4 for washing but Grade 2–3 for rubbing:
- Washing fastness (GB/T 3921): simulates repeated home laundering
- Rubbing fastness (GB/T 3920): dry and wet separately — cuffs and pocket edges fade first
- Light fastness (GB/T 8427): critical for outdoor roles (security, engineering, logistics)
- Perspiration fastness (GB/T 3922): critical for next-to-skin and summer uniforms
- Light + perspiration combined (GB/T 14576): the harshest outdoor scenario
Practical rule: indoor roles focus on washing + rubbing; outdoor roles must add light and light-perspiration tests. Always ask suppliers to report each item separately rather than one blanket "Grade 4".
3. The 6 reports to request at acceptance
- GB 18401 safety class report — mandatory national standard; Class B minimum for skin-contact use. No report, no deal.
- Washing fastness (GB/T 3921) — Grade 4 minimum.
- Rubbing fastness (GB/T 3920) — dry Grade 4, wet Grade 3+.
- Light fastness (GB/T 8427) — Grade 4+ for outdoor roles.
- Fiber content and weight report — GB/T 2910 quantitative analysis plus GSM tolerance, so the promised 65/35 blend is real.
- OEKO-TEX Standard 100 or equivalent — the easy answer for export clients and eco-conscious buyers.
Two checks when reviewing reports: confirm the lab carries CMA/CNAS accreditation, and confirm the sample batch number matches the delivered batch — presenting batch A's report with batch B's goods is the industry's most common trick.
4. Put fastness into the contract
Reports verify this batch; contract clauses protect every batch. Specify per-item fastness floors, grey-scale acceptance, and full-batch return liability in the technical schedule — see 12 technical clauses every uniform contract needs and 3 warranty traps in uniform contracts.
Fastness is only one dimension of fabric quality. For shade consistency and GSM stability, see 4 hard indicators of fabric consistency; to score suppliers across all dimensions, use the 21-dimension supplier screening guide. Hengtun delivers per-batch fastness reports with every workwear order — contact us for swatches and report samples.
