Felted hats are created by either agitating knitted wool yarn in a soapy solution or poking wool roving or batting with felting needles. If you are trying to make your felted hat stiffer, there are ways to shrink the hat so that the fibres become more tightly compressed. Once the felted hat has been properly stiffened with heat and soap, it will be warmer to wear and more wind resistant.
Fill a dish pan with hot water, and pour in 2 tbsp of dish soap.
Immerse the felted hat in the hot soapy water.
Tap the hat with your fingers for 10 minutes, then turn the hat over and tap the other side for another 10 minutes.
Place the felted hat into a washing machine.
Pour enough liquid washing powder into the washing machine for an extra small load.
Wash the hat in hot water.
Dry the felted hat in a clothes dryer on high heat for 30 minutes. The soap and heat will cause the felted hat to shrink and stiffen.