Felting is the process of shrinking wool using hot water and agitation. You can felt wool sweaters in a washing machine, by hand in a sink full of hot water or by boiling them in a pot on the stove. Keep in mind that only 100 per cent animal fibre sweaters will felt, so if your wool sweater contains any plant or synthetic fibres or is labelled "superwash," no amount of boiling will remove the stitch definition.
Fill a large cooking pot half full of water and bring the water to a boil on the stove.
Submerge your wool sweater in the boiling water for five minutes.
Pull the sweater out of the water with tongs to see if it has shrunk enough. If not, return it to the boiling water and check again every five minutes. Agitate the sweater by stirring to speed up the felting process.
Plunge the felted sweater into a sink full of cold water to stop the shrinking process. Allow the sweater to cool completely.
Roll the sweater in a towel to remove excess water, then lay it flat on another towel to dry.