Stretch Content And The Fit That Changes By Noon

A small percentage of elastic fiber transformed how clothing is cut. It also introduced a failure mode that rigid fabrics never had: fit that changes over the course of a day.

Stretch permits a closer pattern

A rigid woven fabric has to include enough ease for the body to move, so a pattern must be cut larger than the body at every point of articulation.

Elastic fiber supplies that movement from the fabric itself, so the pattern can be cut close and still allow sitting, reaching and walking.

This is why contemporary pants and shirts are cut noticeably slimmer than older equivalents, and why an older rigid garment in the same nominal size feels roomy.

Stretch and recovery are separate properties

Stretch is how far the fabric extends. Recovery is how completely and how quickly it returns to its original dimensions afterward.

A fabric can have plenty of the first and little of the second, in which case it extends under load and stays extended.

That is the mechanism behind knees bagging in pants and waistbands loosening through the day. The garment has stretched and not come back.

Recovery depends on fiber and construction

The elastic fiber itself recovers well, but it is a small proportion of the fabric and it is working against the rest of the yarn.

In a fabric with a high proportion of cotton, the cotton deforms and holds its new shape while the elastic tries to pull it back, and the result is partial recovery at best.

Higher elastic content and blends with polyester recover better, which is why some stretch garments hold their shape all day and others do not, at similar stated percentages.

The fiber degrades with heat

Elastane is damaged by high temperatures, and dryer heat is the most common source in normal use.

Once the elastic fibers break, the fabric loses recovery permanently, and the garment goes slack in the areas that flex most.

Washing cool and drying low or on a rack extends the useful fit of a stretch garment considerably, and this is the specific reason those instructions appear on the label.

Fitting a stretch garment in the store

A stretch garment tried on for two minutes will fit closer than it does after four hours, because it has not yet extended under sustained load.

Sitting down in the fitting room, and standing back up, gives a better reading than standing still in front of a mirror.

Buying at the point where a garment feels correct rather than snug allows for the loosening that will occur, which is the reverse of the instinct rigid fabrics train.