Acrylic is a fabric that is prone to stretching. Improper ironing, washing and even time can turn a perfect fit into a jumbled, overhanging nightmare. If you have received a sweater that you like but it is just a little bit too big or if you have one that used to fit but doesn't anymore, don't fret. There is still hope for that treasured garment. Shrinking an acrylic sweater is not only possible, but fairly easy to do with your home washer and dryer.
Place the sweater in the washer alone or with at most one or two other articles of clothing that you wish to shrink.
Set the water temperature to "Warm" and the washing cycle to "Heavy" or "Super Wash" and wash the sweater.
Place the sweater in the dryer.
Set the dryer to a timed-dry of 60 minutes and tumble dry.
Try on the sweater to see if the fit has improved any. Some noticeable shrinking should have occurred.
Repeat this washing and drying cycle until the garment fits to your liking.
It is not the heat, but the repeated washing and drying that actually shrink the garment. Be sure to stop exactly when you think the garment is perfect for you as the shrinking process cannot be reversed. It is not necessary to actually wash the sweater with detergent if all you wish to do is shrink it, however, if you want to add detergent, go ahead. It can't do any harm.
If the garment is labelled "pre-shrunk," then don't expect this process to have much of an effect.