One actually can machine wash most wool sweaters (even the ones with a “dry clean only” tag). The gentle cycle might seem to be the way to go but it’s not gentle enough.
First: Never wash mohair sweaters, those with more than 10% angora fibers, or with special coatings/finishes. Also, don’t wash wool sweaters with an open stitch or with embellishments (beads, spangles, etc.). If you’ve got the yarn sample that comes attached to the tag of many new sweaters, use it to test whether a particular sweater can be washed. Snip off about an inch of the wool, pop it into a mesh bag, and wash it according to the instructions below.
Second: When washing wool sweaters, you want to protect them from agitation. With rare exception, wet wool shrinks when agitated or tumbled in the dryer (with or without heat). Mesh bags are your friend and absolutely necessary. (If you have no mesh bags, hand wash your sweaters.) Also, big, cotton towels are necessary. Thin towels are actually better than thick ones. They cause less fluff/frizz.
If the sweater is not very dirty, use the Dryel or Woolite system of dry cleaning in the dryer. Use this method to clean embellished sweaters. Be certain to put each sweater in a separate mesh bag. Don’t turn embellished sweaters inside out. Use the spot cleaning spray and the corner of the drying cloth to gently clean any spots/stains. Use the minimum amount of dryer time according to the directions on the box. (NOTE: When using Dryel, place mesh bags inside the larger zippered bag and pop the cleaning sheet in with the mesh encased sweaters.) If it’s a heavily or intricately embellished sweater, or has fragile decorations, take it to a specialist. Glass beads beak. Plastic spangles melt. Fringe becomes tangled.
To wash a wool sweater, turn it inside out and put it in a mesh bag. Do not put more than one sweater in each bag. It’s better to wash two or three sweaters in a small load than to try to wash more sweaters in a large one.
Place a large towel on the floor for each sweater. (If items are small, you can put several on each towel.)
Let the machine fill to wash load height with cold water. Add about 1/2 the recommended amount of vegetable based detergent as it fills. Woolite is popular but doesn’t rinse as quickly and thoroughly as Method, Mrs. Meyer’s. Seventh Generation, and other organic and/or vegetable based detergents. You want the detergent to rinse thoroughly in a very brief.
Once the machine has filled, close the lid and let the water and soap agitate for 30 seconds or so. Then open the lid and add the mesh encased sweaters. Push them down. Shut the lid and let the machine agitate as you count to 30. Stop the cycle, advance the program to spin and let the machine spin as you count to 20. Stop the machine, advance the program to rinse, allow it to add water normally, agitate for a count of 30, and then spin as you count to 20. Repeat the rinse/spin cycle. Open the machine, fish out the mesh bags (they’ll be very wet) press the water out of each sopping mesh bundle by hand. (Voluntolding someone with strong hands is very useful but don’t wring them. Wringing = shrunken, misshapen sweaters.)
Open the mesh bags, lay out each sweater on a towel. Gently shape and smooth each sweater to the right shape. Sleeves may be folded over the body (see image). Roll the sweater and towel together. Step on the towel to press out additional water. (You can also just use your hands but it’s kind of fun to dance on your clothes.) If necessary, re-roll sweater in another dry towel and press out more water. Dry flat, if possible. If not, be certain to press out all the water you can and drape over a couple of back-to-back chair backs or a padded/towel wrapped hanger bar.
Don’t forget to let the machine finish the spin cycle so that there’s no standing water left in it.
These instructions are for top loading machines. If front loaders can be stopped, advanced, and restarted, this would also work. Just put the detergent in the bottom of the machine, add the mesh bags, and follow the directions above.
I prefer to machine wash sweaters because dry cleaners often reuse the same solution over and over. (I had a cream sweater that became darker and darker, each time I had it cleaned. As I waited to collect my clothing one day, I noticed the dry cleaning solution was very dark, did some research, and discovered dirty solution was being deposited on my clothing. I began washing the sweater and it’s now cream coloured again.)
Do realize, some sweaters must be dry cleaned by a specialist or spot cleaned and never placed in a dryer. If at all possible, test a bit of the wool before washing. Also, some sweaters, even ones marked “machine washable,” suffer reduction or fall apart when washed or dry cleaned.