Denim QC in Pakistan: Shade, Wash and Measurement

Key Takeaways

• Indigo dyes the yarn surface, so denim shade is judged after the wash under a stated light.

• Shade banding across a dye lot is unfixable at final inspection. It belongs to the dyeing and cutting stages.

• Wash variation between laundries comes from recipe, machine load and water.

• Leg twist and shrinkage surface after laundering, so the pre-production wash test still changes the outcome.

• AQL counts countable defects. Shade is a judgment against an approved reference.

• The laundry's chemistry and effluent record is a second file. It is not a substitute for quality data.

What makes denim different at inspection

Denim is a warp-faced twill. The warp carries the indigo, the weft stays undyed, and that construction separates its defect profile from a plain dyed fabric.

Indigo penetrates the yarn only partly, so untwist a dyed yarn and the inner layers stay colourless, with the colour sitting as a ring at the surface that keeps fading and scratching with wear. Shade cannot be read the way a piece-dyed shade is read, because the surface responds to every step after dyeing, from the indigo dyeing range to the last rinse in the laundry.

Two rules follow. Shade assessment belongs after the actual wash, because a greige reading does not predict the washed result. The reading also needs a fixed light source. Matched shades separate under a different lamp. Industrial colour work holds a standard D65 light source, and change in colour is scored against the grey scale for assessing change in colour.

The defect families, and the stage that owns each

Every denim defect has a home stage. Catching it later costs more.

A denim production programme tracks weight, shade, shrinkage and wash performance together, because one reading proves one roll, not a lot.

Shade banding, and why it reads as a judgment

A large order consumes hundreds of rolls from one dye lot, and rolls that differ in depth leave the mill as a shade range rather than a single colour, so factories group cut parts by shade band and wash each band separately.

The buyer may approve only three or four bands out of ten or twelve. The shade banding and shade sorting methods used on the cutting floor keep one carton to one shade.

Sorting badly rescues nothing. Labelled shade groups keep cut parts traceable from the cutting table to the wash drum; without labels the laundry sorts by eye under whatever light the floor has, and mistakes there cause mass re-washing. The fix is a shade register carrying roll number, dye lot and inspection date.

Shade therefore sits outside the AQL count. It returns a verdict rather than a number.

Wash variation between laundries and between lots

Two laundries running the same recipe rarely produce identical shade. Machine type, load weight, water hardness, enzyme time and bleach concentration all move the result. The second wash stage separates again.

The practical control is one approved wash standard per style, held physically and signed by both sides, and each laundry proves its first bulk wash against that standard before the order runs, because a laundry that fails a trial load fails on fifty thousand pieces.

Colour fastness testing does not replace that trial. Colour fastness to domestic and commercial laundering measures how a fabric behaves under a defined wash condition, and that condition must match the care label.

The recognised tests also cover rubbing and artificial light. Deeply dyed denim generates wet rubbing complaints when fixation was weak, and the wet rub is the condition that matters for a damp, dark garment in wear.

Leg twist, shrinkage and measurement drift after laundering

Leg twist, also called skew or spirality, is the rotation of a garment's leg after washing; it comes from the fabric rather than the sewing and is measured after laundering.

ISO 16322-2 specifies procedures for determining spirality after laundering, and ASTM D3882 covers bow and skew in woven and knitted fabric. Both test the fabric, not the finished pair.

Shrinkage runs the same way. ISO 6330 sets the washing and drying procedures, ISO 3759 governs specimen preparation and measurement, and together they underpin the test methods for garment quality a buyer should write into the order.

Commercial programmes commonly allow about 3 to 5 percent shrinkage either way. Latent shrinkage is the trap. Cotton that was never mechanically pre-shrunk can contract past the allowance, and because Pakistani mills differ in whether they apply a Sanforization step, a pattern cut without accounting for five percent length shrinkage produces a garment five percent short after the first home wash.

Measurement drift is a cutting and sewing fault, and it is visible in-process. Three pieces per size at the 30 to 60 percent mark show a size curve that has moved before the cartons are sealed.

Abrasion, whiskering and hardware

Dry processes create the worn look: whiskering, hand sanding and scraping, then the wet stages. Whiskering and hand scraping are applied by hand on many lines, so placement varies with the operator, and the approved sample is the only reference for whisker position and abrasion depth.

Hardware fails differently. A rivet that pulls through, a button that shears or a zip that sticks is an attachment problem rather than a fabric problem, and it shows up in an in-line pull check and at final inspection. One critical attachment failure fails a lot.

What AQL sampling decides, and what it cannot

Pre-shipment inspection for denim works as it does for other apparel. A sample is drawn from packed cartons against a published sampling table, and each piece is judged against an agreed defect list. The lot passes or fails on the count.

TTI applies C:0 for critical defects, Mj:2.5 for major and Mi:4.0 for minor at general inspection level II. Fabric is graded separately.

ASTM D5430-13 four-point grading charges penalty points by defect length, and shade is checked at grade 4 and above on the grey scale. The AQL sampling method that drives the garment count does not absorb the fabric grade.

AQL handles countable findings: a broken zip, a missing rivet, a measurement outside tolerance. Shade banding, whiskering placement and leg twist are comparisons against the approved reference, not counted findings. Shade is the defect that final inspection catches last and fixes least.

The laundry record beside the quality file

Denim laundries carry a second evidence set. Input chemistry is checked against the ZDHC Manufacturing Restricted Substances List, and discharge against the ZDHC wastewater guidelines. That route is separate from the shade and performance data.

How TTI supports denim QC

Denim moves through the same accredited system as other softlines.

• Fabric and garment testing under ISO/IEC 17025 accreditation, with the scope in PNAC accreditation LAB-022.

• Colour fastness, dimensional stability and wash durability through analytical testing services, plus fabric performance testing as a programme.

• Softlines inspection covering yarn, fabric and denim through inspection and audit services, inside an eight-stage cycle ending in loading supervision.

• AQL sampling at C:0, Mj:2.5 and Mi:4.0, with ASTM D5430-13 four-point grading and shade assessed against the approved reference.

• ZDHC MRSL v3.1 approved certifier at Level 1 and Level 2, and ZDHC approved wastewater laboratory status.

• Coverage from Lahore, Karachi, Faisalabad and Sialkot, through the textiles and apparel division.

TTI inspects and reports. It does not rework goods, coach lines to pass, or soften a finding for the factory.

FAQ

What causes shade banding in denim? Shade banding comes from variation in the dyeing process, most often across rolls in one dye lot, because indigo sits on the yarn surface and dyes in multiple dips, so shifts in bath concentration, squeeze pressure or oxidation change the depth. Each roll can read differently, so buyers track Pakistan denim suppliers closely.

Why is denim shade checked after the wash and not before? The wash creates the shade the consumer sees. The surface ring of indigo responds to desizing, enzymes, bleach and abrasion, so a greige reading does not predict the finished result. Shade is therefore assessed after the wash, under a fixed D65 light source, against an approved reference.

Can leg twist be fixed once the garment is washed? No. Leg twist is a property of the fabric that washing releases, so it cannot be corrected on a finished pair, and it is prevented upstream through fabric construction and finishing, measured after laundering under ISO 16322-2 or as bow and skew under ASTM D3882.

Which tests prove denim shrinkage and colour fastness? Dimensional change is tested with ISO 6330 for the washing and drying procedure and ISO 3759 for specimen preparation and measurement. Colour fastness runs through the ISO 105 series: ISO 105-C06 for laundering, ISO 105-X12 for rubbing and ISO 105-B02 for light, with results scored on the grey scale.

Does AQL sampling cover shade? Not as a counted defect. AQL handles countable findings such as a broken zip or a measurement outside tolerance. Shade is a comparison against an approved reference. It produces a judgment rather than a number. Fabric shade is graded separately at grade 4 and above on the grey scale.

Conclusion

• Denim's defect profile is set by its construction. The warp carries an indigo ring, and the wash decides the final shade.

• Shade banding and side-to-side shading are dyeing and cutting stage problems. Final inspection can only record them.

• Wash variation is a laundry control. It is proven on a first bulk trial against one approved standard.

• Leg twist, shrinkage and measurement drift are cheaper to catch before cutting than after the wash.

Book denim testing and inspection with TTI Testing Laboratories. UAN 111 786 001. Test the fabric, inspect the wash, grade the shade.

References

1. Denim dyeing process with indigo dyes (warp-dyed construction, surface ring dyeing, cross-shade variation by dyeing method), Textile Learner, https://textilelearner.net/denim-dyeing-with-indigo-dyes/

2. Industrial colour assessment with standard light D65, JUST Normlicht, https://www.just-normlicht.com/en/industrial-color-assessment-d65.html

3. ISO 105-A02:1993, Textiles. Tests for colour fastness. Part A02: Grey scale for assessing change in colour, International Organization for Standardization, https://www.iso.org/standard/3785.html

4. ISO 105-C06:2010, Textiles. Tests for colour fastness. Part C06: Colour fastness to domestic and commercial laundering, International Organization for Standardization, https://www.iso.org/standard/51276.html

5. ISO 105-X12:2016, Textiles. Tests for colour fastness. Part X12: Colour fastness to rubbing, International Organization for Standardization, https://www.iso.org/standard/65207.html

6. ISO 105-B02:2014, Textiles. Tests for colour fastness. Part B02: Colour fastness to artificial light: Xenon arc fading lamp test, International Organization for Standardization, https://www.iso.org/standard/65209.html

7. ISO 16322-2:2021, Textiles. Determination of spirality after laundering. Part 2: Woven and knitted fabrics, International Organization for Standardization, https://www.iso.org/standard/78781.html

8. ISO 6330:2021, Textiles. Domestic washing and drying procedures for textile testing, International Organization for Standardization, https://www.iso.org/standard/75934.html

9. ISO 3759:2011, Textiles. Preparation, marking and measuring of fabric specimens and garments in tests for determination of dimensional change, International Organization for Standardization, https://www.iso.org/standard/57309.html

10. ASTM D3882-08(2020), Standard test method for bow and skew in woven and knitted fabrics, ASTM International, https://www.astm.org/d3882-08r20.html

11. ASTM D5430-13, Standard Test Methods for Visually Inspecting and Grading Fabrics, ASTM International, https://www.astm.org/d5430-13.html

12. Shade variation and shade banding control in denim wash, GoldnFiber, https://www.goldnfiber.com/?p=3270

13. Denim dry processes: whiskering, laser whiskering and hand scraping, Textile Study Center, https://textilestudycenter.com/denim-dry-processes-part-1/

14. Pakistan jeans export report, January to June 2024 against 2023, Denimsandjeans, https://www.denimsandjeans.com/latest-denim-reports/pakistan-jeans-export-report-2024-vs-2024-jan-to-jun/67772

15. ANSI/ASQ Z1.4 and AQL inspection explained, QIMA, https://www.qima.com/aql-acceptable-quality-limit

16. ZDHC Manufacturing Restricted Substances List, Roadmap to Zero, https://www.roadmaptozero.com/mrsl

17. ZDHC Wastewater Guidelines Version 2.2, ZDHC Roadmap to Zero, https://downloads.roadmaptozero.com/output/ZDHC-Wastewater-Guidelines

18. Accreditation scope LAB-022 (ISO/IEC 17025:2017, first granted 13 May 2006, valid to 8 August 2027), Pakistan National Accreditation Council, https://pnac.gov.pk/pdfFiles/LAB-022

19. Analytical testing services, TTI Testing Laboratories, https://ttilabs.net/testing

20. Inspection and audit services (softlines stages, denim within textiles and raw materials), TTI Testing Laboratories, https://ttilabs.net/inspection

21. Textiles and apparel testing, TTI Testing Laboratories, https://ttilabs.net/textiles-apparel

22. Contact and offices, TTI Testing Laboratories, https://ttilabs.net/contact

23. Chapter 7 Textiles and Chapter 9 Inspection Services (textile defect families, AQL ANSI/ASQ Z1.4-2008 C:0 / Mj:2.5 / Mi:4.0 at general inspection level II, ASTM D5430-13 four-point fabric grading with shade at grade 4 and above, eight-stage inspection cycle), TTI Global Reference Publication, June 2026, Authoritative Edition, TTI Testing Laboratories. The publication is an internal TTI document with no public URL.