What is bowing?#
Bowing is a fabric distortion where the weft yarns (in woven fabric) or the courses (in knitted fabric) curve across the width instead of running straight from selvedge to selvedge. The curve can be like a smile, with the center lagging behind the edges, or like a frown, with the center ahead.
Bowing is often invisible on plain fabrics until the garment is washed and relaxes. On striped, checked and printed fabrics, it is obvious straight away. See bowing and skewing for the measurement method.
What it looks like#
- Weft stripes or check lines curving across the fabric.
- On garments, horizontal stripes that curve across the chest or back.
- Checks that do not match across seams because the lines are curved.
- Plain garments that hang unevenly after washing.
Where it occurs#
- Woven stripes and checks, especially yarn-dyed shirting.
- Printed fabrics with horizontal elements.
- Knitted stripes and yarn-dyed knits.
- Fabrics finished on stenters without effective weft straightening.
Likely causes#
Bowing happens when the center of the fabric travels at a different speed or tension from its edges during processing. On a stenter, the edges are held by clips or pins, while the center is supported only by the fabric itself. If the center is dragged back or pushed forward, the weft curves.
Machine-related causes#
- Uneven tension across the width in wet processing and finishing.
- Stenter feeding: center of fabric sagging or dragging.
- Weft straightener: bow rollers not set or sensors not working.
- Worn or misaligned rollers causing uneven travel.
Material-related causes#
- Uneven pick density across the width from weaving.
- Fabric structure with different shrinkage at the center and edges.
Operator and process-related causes#
- Settings changed during the run without recording.
- Batching rolls unevenly so that fabric is distorted in storage.
Method-related causes#
- No bow check at fabric inspection.
- Cutting to the fabric edge instead of aligning to stripes on distorted fabric.
- No agreed bow limit in the fabric specification.
How to confirm the cause#
- Measure bow at the beginning, middle and end of several rolls.
- Compare rolls from the same lot and finishing run.
- Check finishing records for straightener use and settings.
- Count picks at the center and edges of the fabric.
- Wash a sample and remeasure: some bowing appears or increases after relaxation.
Immediate containment#
- Stop cutting striped or checked fabric with bow above the agreed limit.
- Separate affected rolls and label them.
- For plain fabric, check whether garments will hang correctly after washing.
- Discuss with the supplier and buyer whether rolls can be reprocessed or accepted with special cutting.
Corrective action#
| Cause | Corrective action |
|---|---|
| Uneven tension in finishing | Refinish with weft straightener set and working |
| Straightener faults | Repair and calibrate sensors and rollers |
| Pick density variation | Address in weaving for future lots |
| Cutting distorted fabric | Align patterns to the stripe or weft; allow extra fabric |
Preventive action#
- Bow limits and test method in the fabric specification.
- Bow measurement in incoming fabric inspection, recorded with the 4-point results. See 4-point inspection.
- Supplier process control: straighteners on finishing ranges for stripe and check fabrics.
- Marker planning for stripes and checks that includes matching points.
Inspection notes#
- Measure bow on flat, relaxed fabric without tension.
- On garments, check stripe alignment at the chest, back and hem.
- Visible bow on striped or checked garments is commonly a major defect.
Example investigation#
A yarn-dyed check shirting shows weft lines curving up to 2.5 cm across a 150 cm width on some rolls and almost none on others. All affected rolls come from the second half of one finishing run. The straightener log shows its sensor faulted halfway through the run and the machine continued without automatic correction. The affected rolls were refinished, and a stop rule was added when the straightener faults.
Questions to ask the fabric supplier#
- Which finishing range was used, and does it have an automatic weft straightener?
- Were straightener faults recorded during the run?
- What bow limit does the mill work to, and how is it measured?
- Was the fabric relaxed before final finishing?
- Can the mill supply bow measurements per roll with the packing list?
Clear answers help decide whether rolls can be refinished or whether the problem will repeat on the next lot.
Factory checklist#
- Bow limit agreed in the fabric specification
- Bow measured at fabric inspection on every roll of stripes and checks
- Rolls above limit separated before cutting
- Marker planned for stripe matching
- Supplier informed with measurements