Down feather winter jackets are some of the warmest jackets you can wear. Just like the feathers that keep birds warm, down feathers work by trapping pockets of air in between the feathers to act as insulation from the cold. After wearing a down feather jacket for a long time, you might notice that the jacket will lose its "puffed up" feeling, becoming thinner and less warm. Down feather jackets are the only jackets that need to be puffed up occasionally. Fortunately it is easy to puff up your jacket with warm air.
Close all the zippers and pockets on the jacket. Place the down jacket into the washing machine and wash it in cold water with detergent. Remove the jacket once the wash cycle has ended and place it into the dryer.
Place three to five clean tennis balls into the dryer with the jacket. Set the dryer on low heat and tumble dry. The tennis balls will hit the jacket as it tumbles, allowing the warm air to move through the jacket and the clumps of feathers, breaking up the clumps and puffing up the jacket.
Check the jacket once the cycle has ended. If the jacket still seems a little damp, reset the dryer and put it through one more cycle.