Why your bra underwire pokes after washing

An underwire that pokes through the fabric casing after washing is one of the more common and frustrating bra problems. It is also one with clear causes and straightforward responses — it is not random damage, it is the result of two identifiable failure modes.

The two causes

Wire migration happens when the wire moves along its casing and the end finds a weak point in the fabric. The casing — the channel of fabric through which the wire runs — has an open end that is closed during manufacture, typically with a bar tack or a close-stitched seam. When this closure weakens with wear and washing, the wire end finds its way through.

Migration is accelerated by machine washing (the mechanical agitation works the wire along the casing) and by a bra that is too small in the cup (the wire is under more tension than the construction was designed for, stressing the casing closure with every movement).

Fabric fatigue at the casing itself — usually at the centre-front or underarm end of the wire — is the second cause. The casing fabric has a finite number of flexions before it thins and develops a small hole through which the wire end penetrates. This happens regardless of washing method, simply as a function of wear frequency, and is more common in bras that are worn without adequate rotation.

Diagnosis

Check the end of the wire. Press the fabric around the casing at the centre-front and the underarm end. If the wire has migrated, you will feel the end close to the surface at the casing closure rather than in the middle of the casing run.

Check the casing fabric. Feel for thin spots or small perforations in the fabric at the points where the casing is under most stress: the end points and any point where the wire runs close to a seam.

Repair and prevention

For migration: locate the casing closure, open a small amount of the seam, and reposition the wire back to its correct position. Re-close the seam with small, tight stitches. Apply a small piece of iron-on mending tape or a hand-stitched patch to the interior of the casing at the end, to reinforce the closure point.

For casing fatigue: the repair is a fabric patch on the interior at the thin or perforated point, stitched around all four sides. Iron-on mending tape works for temporary repair; hand-stitching with a patch of matching fabric (a spare piece of casing tape from a haberdasher) is more durable.

For prevention: hand-wash bras or use a mesh laundry bag in the machine on a cold, delicate cycle. For hand-washing technique, the silk care guide describes the fold-not-wring principle that applies equally to bra care. Rotate across several bras rather than wearing one frequently — elastic and casing both benefit from rest days.

When a bra has reached the repair stage twice in the same location, it is usually at the end of its useful life. The guide to how often to replace your bra covers the replacement decision.