Fleece is originally made from sheep's wool, and dates back in clothing to hundreds of years ago. Today many garments are made from synthetic or "polar" fleece, which is a blend of polyester and fleece that creates a breathable, warm fabric. Polar fleece is said to be twice as warm as wool yet more lightweight. Synthetic fleece is cheaper than real fleece but can be resistant to shrinking. If you need to shrink your fleece, expose it repeatedly to very high temperatures, such as boiling water and hot air.
Fill your cooking pot with water and bring the water to a boil. Make sure the cooking pot you choose is big enough to fit your fleece. Once the water has come to a boil, completely immerse your fleece in the water and lower the heat to medium.
Remove your fleece from the boiling water after five minutes using a wooden cooking utensil. Be careful not to burn your fingers or skin during this step.
Carry the fleece to your washing machine and place inside. Turn the settings on the machine to the hottest water temperature, usually marked "whites" or "hot," depending on your machine, and place the cycle setting on "normal". Do not add washing powder, as you are not washing your fleece, but shrinking it. Allow the machine to finish its cycle.
Remove the fleece from the washing machine and place it in the clothing dryer. Set the dryer to the highest temperature possible, for the longest cycle.
Remove the fleece from the dryer. It should be shrunk. Your garment may stretch out again with wear, but repeating the steps will ensure that your fleece shrinks back down to a smaller size.
Be careful not to burn yourself when working with hot water. You may want to wear thick plastic gloves that cover up to your elbows as protection.