Blend claim on a mixed warp beam
A weaving co-operative in Ichalkaranji supplies 500 kg of grey fabric to a Pune shirtings buyer. The purchase order states the warp is 60% cotton / 40% polyester. After desizing and a pilot reactive dyeing, the buyer reports two problems: the fabric shrinks 7–8% in warp after a 60°C wash, against the 2% stated on the sample tag, and the dyed shade shows pale streaks along some warp ends. The co-operative's records show two warp beams were sourced from different suppliers and mixed at sizing; one beam was labelled 2/40s cotton, the other 'poly-cotton 2/40s'. There is no retained yarn sample from either beam. The buyer demands a fibre identification report within a week and threatens to cancel the balance 1,500 m. The unit has a burn-test kit, a simple microscope, and access to a district testing laboratory that can run solubility tests but takes ten days.
1. Design a one-week identification plan using the burn-test kit, the microscope and the district laboratory. State what you would sample and the observation that would confirm polyester in the pale warp ends.
Read the worked answer
Sampling. Take yarn from one pale warp end in the dyed fabric, one normal dyed end, and, if any greige remains, from each of the two beams. Include known cotton and known polyester controls. Dyed fabric alone can mislead because dye masks appearance, though not burning behaviour.
Burn test, day 1. Cotton ignites and burns like paper, smells of burning paper and leaves grey fluffy ash. Polyester shrinks from the flame, melts, gives black smoke and a sweet-chemical odour, and leaves a hard black bead that does not crush. A blend shows a mixed odour plus both ash and bead. This identifies the fibre type but cannot quantify 60:40 reliably.
Microscope, day 1–2. Cotton is a flat, ribbon-like fibre with convolutions; polyester is a smooth, uniform cylinder with a bright highlight. Finding smooth cylindrical filaments in the pale ends confirms polyester there.
District laboratory. Send samples immediately for solubility testing. Cotton dissolves in 70% sulphuric acid; polyester does not. Phenol or m-cresol dissolves polyester. Sequential dissolution gives an approximate blend ratio, but the ten-day turnaround means you must issue an interim report and request expedited testing.
2. The buyer's 7–8% warp shrinkage is far above the 2% tag. Is the mixed beam enough to explain it? What else would you examine before accepting the claim?
Read the worked answer
The mixed beam explains the streaks better than the shrinkage. A polyester-rich warp end would not shrink like cotton; if anything, it would reduce average warp shrinkage. The pale ends are consistent with reactive dye failing to bond to polyester, because reactive dyes fix to cellulose. So the beam mix is a credible cause of streakiness, but it is not sufficient on its own to explain 7–8% warp shrinkage.
Check the cotton side of the claim. Look at the finishing route: was the fabric mechanically compacted or sanforised? A cotton warp woven at high tension and finished without relaxation can shrink 7–8% on washing. Check warp yarn twist, weave crimp, loom tension and beam quality. Also check the buyer's test method: 60°C wash, detergent, drying method and number of cycles can all raise shrinkage. The 2% tag may refer to a different test.
Decide with evidence. Test both pale and normal ends separately, and test a control fabric known to be 60:40. If both ends shrink similarly, the beam mix is not the cause of the shrinkage claim; the finishing and test method need investigation.
3. What commercial and quality action should the co-operative take before the balance 1,500 m is dispatched?
Read the worked answer
Stop dispatch and segregate. Keep the remaining 1,500 m by beam and roll, retain at least one metre from each roll as a sealed sample, and do not certify the 60:40 blend until the laboratory result is available. The one-week deadline is tight, so send the solubility samples on day 1 and issue a provisional report that clearly states the method and the uncertainty.
Protect the commercial position. Offer the buyer a choice: hold the balance pending the report, sort and price the streaky rolls as second quality, or replace them. A cancellation of 1,500 m is likely to cost more than expedited testing, so ask the laboratory for a priority turnaround and record that request.
Fix the root cause. Introduce incoming-beam labelling with supplier, count, blend and batch number; keep a yarn sample from every beam; and prohibit mixing beams at sizing without a recorded blend declaration. Add a simple incoming burn and microscope check, because it catches gross mislabelling before weaving. If the supplier's 60:40 claim cannot be supported, recover the loss from that supplier rather than passing an unverified claim to the buyer.