Secondly, if you really want to put the washing machine, you have to put it in a washing bag, choose the "wool washing" or "gentle washing" gear on the washing machine, and inject professional silk/wool laundry detergent. Ordinary laundry detergent is bad for wool products.
Third, you'd better send the sweater to the dry cleaner. If you wash it at home, it is best to wash it gently with a big basin and professional detergent. If there is no professional detergent, you can soak it in tea (cold water, not hot water) for a while, then soak it gently and rinse it with clear water.
Finally, don't expose the washed sweater to the sun. It is best to dry in a cool and ventilated place. When drying, it is not suitable to hang it directly on the hanger to avoid the deformation of the sweater. It is best to use a special sweater drying rack, that is, a porous and rain-leaking flat plate, and hang the sweater flat with a tether and a hook. If you really don't have that thing, find a net bag to put the sweater in and hang it to dry. After a few hours, take it out and put it in at a different angle to make sure it is dry.