Q: Why does a zipper twist after washing and drying?
Washing adds heat, water and mechanical action, which release tension built into the tape and the seam. Twisting at this stage is usually a combination of tape behaviour and the care route, so compare a loose length with a sewn sample.
- Wash a sewn sample and a loose length of the same tape together, then compare twist.
- Note the wash temperature, spin speed and drying method actually used.
- Check whether the garment was tumble dried above the tape's recommended range.
- Measure tape width and length before and after to detect shrinkage imbalance across the tape.
- Inspect the seam for puckering that pulls the tape into a spiral.
If the loose tape twists as well, the tape is the cause. If only the sewn sample twists, the seam or the care route is responsible. A care trial of three to five washes at the intended condition is a practical way to confirm the pattern before the style goes into bulk.