The Reason Why Clothes in the Laundry Shrink When You Wash Them

College students and others living on their own for the first time know the feeling well. You toss a load of laundry in the washer or dryer and come back to find your sweater, shirt, or pants have becomes doll accessories, shrinking past the point of comfort and fit. It’s a disturbing discovery.

How does this happen? And how can you prevent the dreaded shrinkage?

What's in your laundry cart matters

First, it helps to understand the effect of moisture and heat on different kinds of fabrics. Material like wool is prone to felting shrinkage, where the surface scales of animal fibers begin to compress and knit themselves together. Relaxation shrinkage is when natural fibers swell when immersed in water. (Cotton won’t typically shrink this way, but silk will.)

The greatest chance for damage comes in consolidation shrinkage, when moisture and heat is combined with agitation from the washer and dryer to release the tension in the fibers, deforming the fabric. If not used properly, this combination is the reason why clothing can pop out of the dryer shriveled.

The benefits of pre-shrunk laundry

Certain fabrics and how they're manufactured can increase a piece of clothing's potential to be re-sized in the wash. Natural fibers are prone to it; synthetics aren’t. A woven material, like denim, is more durable than a knitted fabric, like a T-shirt. Anything labeled “pre-shrunk” is, of course, more durable. That means the manufacturer already exposed the material to consolidation shrinkage, so the fit you have is largely the fit that will remain.

Reading the laundry symbols

When a pre-shrunk item isn’t available, preventing shrinkage comes down to how you handle your laundry. For the most part, reading the care tag instructions will give you all the information you need. The tag will advise you on water temperature, agitation, and dryer temperature. The general rule, however, is that the cooler, the better. Washers and dryers on low heat settings are less likely to promote shrinkage than high heat settings. The speed at which the machine’s drum spins also influences shrinkage, as agitation is part of consolidation shrinkage.

Mastering your dirty laundry

There’s actually more you can do beyond following the tag’s instructions. To handle clothing that's ultra-delicate, the tumbling action of a front-loading washer is more gentle than top-loaders, which use mechanical agitation to spin out clothes. Air-drying clothes also removes damaging heat and movement from the dryer. If air-drying isn’t feasible, you can put items on low heat just long enough to get them from wet to damp and then let them dry out.

The most vulnerable garments, like wool and silk, should probably be hand-washed or dry-cleaned.

When hot water is good for laundry

If cold settings are the default, why use hot water settings at all? Hot water is good for sanitizing purposes, like washing underwear, bed sheets, and towels. Synthetic fibers like nylon and polyester also hold up well to warmer settings—and may need it, since these fibers are often used in gym clothes. Otherwise, it's best to stay cool.