Why do polo shirt collars curl, and how do I prevent it?

Short answer: Polo collar curling usually comes from the collar itself. Most polos use a flat-knit collar, knitted to shape on a flat machine. If the knit tension, yarn twist or structure is unbalanced, the collar naturally curls, and washing releases the stress. If the collar shrinks differently from the body or placket, the collar edge can wave or the points lift. Poor setting during knitting or finishing, too light a yarn and lack of support in the collar stand also contribute. Prevent it by approving collars from a supplier that knits them with balanced tension, matching shrinkage of collar and body, considering a light stabilising interlining in the collar stand for woven-style collars, and testing collars after several washes before bulk.

Common causes

• Unbalanced knit tension or yarn twist in the flat-knit collar.
• Collar and body shrinking by different amounts.
• Light collar yarn that lacks body.
• Poor heat setting or finishing of the collar.
• Tight stitching where collar joins the neck.

Prevention

• Specify collar yarn, gauge and weight, and approve physical collars.
• Ask the collar supplier how collars are set and finished.
• Check dimensional change of collar and body with ISO 5077 after ISO 6330 washing.
• Use the right stitch tension when attaching the collar.
• Advise customers to reshape collars while damp and avoid high heat.

Testing

Wash sample shirts five to ten times, dry as the care label allows, and lay the collars flat. Compare curling, waviness and collar length with new samples.

A worked example

For the shirts in the question, the collars shrink about 6% while the body shrinks 3%, pulling the collar edge into waves. The brand switches to a collar supplier that heat sets collars, matches shrinkage within 1%, and confirms collars stay flat after ten washes.

Collar construction options

Flat-knit rib collars are standard for knit polos. Self-fabric collars cut from the body piqué, sometimes with a light fusible interlining, give a softer, more casual look but can curl at the points if the fabric is unstable. Woven collars with interlining, as on some hybrid polos, stay flat but feel more formal. Choose the construction for the look, then test it after washing.

Limits

Some movement after many washes is normal for flat-knit collars. Pressing restores most of the shape.

Facts, recommendations and uncertainty

Established: collar curling comes mainly from flat-knit collar tension and shrinkage mismatch. Recommendation: specify and approve collars, match shrinkage and test after washing. Uncertain: how many washes your customers expect before the collar shows wear.

Sources and further reading

• ISO 5077:2007 — Determination of dimensional change in washing and drying
• ISO 6330:2021 — Domestic washing and drying procedures for textile testing

Standards and regulations are referenced by their published scope. Test parameters, cycles and pass levels should be agreed with your laboratory for the specific product; legal requirements should be confirmed for each destination market.