Shrinkage in denim is the reduction in length and width after the fabric or garment is washed and dried, caused by the release of tension put into the yarns during spinning, weaving and finishing. For sanforised rigid denim, shrinkage is typically within about 3 percent in both directions, while stretch denim usually shrinks more in the weft, often 5 to 8 percent or beyond depending on the elastane content and the wash.
What counts as acceptable depends on how the fabric will be used. A garment that goes through a heavy industrial wash before sale can tolerate more raw fabric shrinkage than one sold rigid and unwashed, because the pattern can be adjusted for the known loss.
Why denim shrinks
Cotton yarn is stretched during spinning and sizing, and the warp is held under tension on the loom. Finishing ranges also pull the fabric. When water enters the fibre, it swells and the yarns relax towards their natural crimp, so the fabric gets shorter and narrower. Heat in tumble drying adds further relaxation.
Sanforising, also called compressive shrinkage, mechanically shrinks the fabric in the warp direction by feeding it through a rubber belt against a heated cylinder. It removes most of the potential warp shrinkage before the fabric leaves the mill. Width shrinkage is controlled by the stenter settings and, in stretch fabrics, by the recovery of the elastane.
Typical figures
- Sanforised rigid denim: typically up to about 3 percent in warp and weft.
- Unsanforised or loomstate rigid denim: often 8 to 10 percent, intended for shrink-to-fit garments.
- Comfort stretch: usually similar to rigid in the warp, slightly more in the weft.
- Stretch denim with elastane: typically higher in the weft, sometimes 10 percent or more after a hot wash, with the warp close to rigid figures.
Testing, tolerances and the specification
Dimensional change is tested by marking a measured square on the fabric, washing and drying it under a defined programme and measuring again. The common methods are ISO 6330 for the wash procedure with ISO 5077 for the measurement, or AATCC 135 in markets that use American standards. The wash temperature, drying method and number of cycles change the result, so the test conditions must be written into the specification.
Tolerance is usually agreed as a maximum figure per direction, for example minus 3 percent, and the mill's test report is compared with an independent result on a sealed sample. Garment makers add the agreed shrinkage to their pattern allowances, so a fabric that exceeds tolerance causes fit problems across the whole order.
State the test method, wash temperature, drying method and number of cycles. State the maximum shrinkage in each direction and whether it applies to the fabric or to the finished garment. For stretch fabrics add a growth or recovery figure, since a fabric that shrinks a little and grows a lot is just as hard to fit.
How we help
We check sanforising and testing equipment during mill visits, send sealed samples to an NABL-accredited lab for dimensional change under your own wash programme, and supervise loading. You get weekly updates, one approved supplier plus one backup, and a free 20-minute sourcing review.