Q: Why does the zipper bulge after the garment is washed?
Bulging after washing is a shrinkage mismatch between the tape and the shell fabric, or heat deformation of the teeth. Measuring the same marked lengths before and after the wash separates the two causes quickly.
- Measure a marked length of zipper tape and the adjacent shell before washing.
- Wash a sample at the intended care condition and measure both again.
- Compare shrinkage; a difference of roughly one percent or more between tape and shell can produce visible bulge.
- Check wash temperature and drying method against the care label, because heat above the tape's comfort range can distort moulded elements.
- Examine whether the bulge is local at the seam or spread along the whole opening.
Local bulge at the seam is a sewing or interlining issue, while uniform bulge along the opening is a shrinkage mismatch. Ask the maker for tape shrinkage data for the specific tape rather than a general figure. A sewn sample washed before bulk cutting is the practical control.