A wool blanket that you wash as you would your day-to-day laundry may result in the blanket morphing into a tiny version of its original self. Many wool blankets may be washed in a machine by soaking and rinsing the blanket, avoiding the agitation portion of the wash cycle. Agitation rubs the wool fibers, which may cause them to irreversibly shrink. If the tag on the blanket specifies "Dry Clean Only," do not wash it in the machine.
Fill a top-loading washing machine with lukewarm water. Add mild laundry detergent, using your favorite detergent designed for delicate items or wool, using the amount specified on the detergent package.
Agitate the water by turning the machine's setting knob to a wash cycle, or by mixing the water with your hand. Rinse your hand afterwards if you mixed the water by hand.
Place the wool blanket in the water, pushing it down to submerge it. Allow it to sit for 10 minutes or so.
Swish the blanket around slightly in the water, but avoid rubbing the blanket against itself, as this causes felting and may shrink the blanket.
Turn the washing machine dial to the "Spin" cycle and close the lid. Open the lid when the cycle is complete.
Set the washing machine dial to "Rinse" or "Fill" to fill it with warm water while the blanket is still inside. Stop the machine from draining or agitating by opening the lid once the drum is nearly full.
Allow the blanket to soak for 10 to 15 minutes, then plunge it up and down to release soapy residue. Do not rub the blanket against itself.
Set the machine dial to "Spin" again and close the lid, allowing the machine to spin most of the water out of the blanket.
Lift the blanket and hang it over a clothesline to dry, or set it atop a sheet, spread flat, in a place where it may dry.