How to wash sweaters at home without shrinking them

Almost everyone has one: the sweater that went into the wash in an adult size and came out sized for a ten-year-old.

It is tempting to blame the water, but wool does not shrink because it got wet. It shrinks because it got wet, warm and tossed around at the same time. Each wool fiber is covered in tiny scales, and heat plus agitation makes those scales lock together. Once they lock, the fabric tightens and thickens, and it does not come back.

Take away the heat and the rough handling, and many wool and cashmere sweaters can be washed at home. Here is how.

Read the label first

The care label is the one step not to skip.

• Dry clean only: send it out. Lined, beaded or tailored knits are worth sending out too.
• Hand wash: this guide is for you.
• Machine wash on a gentle or wool cycle: you can use the machine, with the precautions further down.

Wash less often than you think

Wool resists odors better than most fabrics, and a sweater worn over a shirt does not need a wash after every wear. Air it out overnight over a chair back, dab a small mark with a damp cloth, and save the full wash for when it really needs one.

Fewer washes means less wear, fewer chances to shrink, and less pilling.

Treat stains before the wash

Spot-treat stains first, while the sweater is dry. Dab a little wool wash onto the mark with your fingertip or a soft cloth and let it sit for a few minutes. Do not scrub. Rubbing wet wool is exactly the agitation that starts felting.

For anything oily or stubborn, or on a sweater you love, ask a cleaner before you experiment.

The hand wash, step by step

Before you start, measure the sweater: chest width, body length and sleeve length. Or lay it on a sheet of kraft paper and trace around it. You will use those measurements when it dries.

1. Fill a clean sink or basin with cool to lukewarm water. Never hot.
2. Add wool wash in the amount on the bottle, and swish it through the water before the sweater goes in.
3. Turn the sweater inside out, push it under, and press gently until it is soaked through.
4. Let it soak for the time the bottle suggests, then squeeze the suds through it a few times. No rubbing, no scrubbing, no twisting.
5. Unless your wash is labeled no-rinse, drain the basin and refill it with water at the same temperature to rinse. A sudden swing from warm to cold can tighten wool too, so keep the rinse close to the wash.
6. Press the water out against the side of the basin. Lift the sweater out in a bundle with both hands, so the wet weight does not stretch it.

Never wring it

Wringing stretches wet wool and twists the fibers out of shape. Instead, lay the sweater on a large dry towel, roll the towel up from one end with the sweater inside, and press down along the roll. Unroll it, and the sweater should be damp, not dripping. For a heavy knit, repeat with a second dry towel.

Dry it horizontally, and reshape it

Wet wool stretches under its own weight, so never hang a wet sweater. Lay it out on a mesh drying rack, where air reaches both sides, and pat it back to the measurements you took. Ease the shoulders square, line up the hem, and lay the sleeves alongside the body.

Keep the rack away from radiators, heat vents and direct sun. Turn the sweater over once the top feels dry, usually after several hours. A thick knit can take a day or more.

Never put a wool sweater in the dryer, even on low.

When you can use the machine

If the label allows machine washing, use the wool or hand-wash cycle, cold water and wool wash. Put each sweater in its own mesh laundry bag to cut down on rubbing and snagging against other clothes and the drum. Skip the dryer, and finish on the rack the same way.

Cotton and acrylic sweaters are more forgiving than wool, but they still hold their shape better drying on a rack than tumbling in a hot dryer.

Steam between washes

A handheld steamer earns a spot next to the drying rack. A few passes freshen a sweater between washes, relax wrinkles from a drawer or a suitcase, and soften the crease in a sleeve that was folded too long.

Hold the steamer a little away from the knit, keep your free hand out of the steam, and move it slowly. There is no need to press the head into the fabric, and never steam a sweater while someone is wearing it.

What to actually buy

A sink and a towel will get you started. These turn it into a routine instead of a risk.

The wash. A wool and cashmere wash, a concentrated plant-based detergent made for wool, cashmere, merino, mohair and blends, in a cedarwood and lavender scent.

The bags. A five-piece set of mesh laundry bags in three sizes, with covered zippers, for the sweaters that go in the machine.

The rack. A mesh sweater drying rack with a 26 by 26 inch surface. Its legs are set in from the corners so it stands on a counter or the top of the washer, it stacks with a second rack on a big wash day, and it folds in half to store.

The steamer. A handheld clothes steamer that heats up in under a minute, with a removable tank that gives up to 20 minutes of steam.

Who this is not for

• If the label says dry clean only, or the sweater is lined, beaded or tailored, a professional cleaner is the safer choice.
• If a sweater has already shrunk and felted, washing will not reverse it. Let it become the cozy house sweater it now is.
• If you own one good sweater and wear it twice a winter, a trip to the cleaner once a season may be less trouble than a routine.

Start on any Monday

This week, pick the sweater that needs it most and give it the full treatment: measurements first, then cool water, wool wash, the towel roll and the rack.

Keep the measurements on a note by the sink for next time. After the second wash, the whole thing takes about fifteen minutes of hands-on time, plus a day of waiting.