Originally Posted by
AdamDZ
All wool can be washed in a machine and tumble dried but it has to be gentle and cold wash cycle with mild detergents, and low heat drying. Hot water and hot drying will destroy wool. Strong detergents or over-saturation in detergent will also harm wool and often make it smell funny and itch your skin as the detergent doesn't get rinsed properly. It's best to put them in net-bags to avoid stretching in wash. I wash my stuff once a week at a laundromat.
Adam
Just realize that unless you have a pre-shrunk garment, wool is affected by heat and agitation. Microscopically, the overlapping "plate" or "shingle" structure of the fiber will retract and lock when heated and agitated; so if you use a washing machine you're best off if it has a handwash cycle, not just a delicates/low cycle. Tumble drying further agitates the fibers, increasing the chance at fiber retratction; lay the garment flat on a beach towel, lightly stretch it to the point of some resistance (don't pull/over-stretch it), and roll the whole thing up in the towel. Press it to remove excess water, and dry it on a rack if you really want the garment to keep its fit.