Down jacket and tennis balls

My wife loves her down jacket, so when it came time to cleaning it at the end of the winter season, she was filled with apprehension. She had heard of some trick to make the job possible - not lethal - for the garment, but didn't remember exactly what it was when, with tremendous anxiety, she dropped the garment into the washing machine.

At the end of the cycle, she pulled the jacket out: It looked just like a formless, downed, dead cat. Visibly, the jacket was ruined. I searched on the web and found that by tumble-drying the parka along with a few tennis balls or a pair of clean sneakers, it would resurrect.

This was precisely what my wife was told as she remembered the magic trick. That's what she did and the jacket returned to its prior, fluffy nature. Really hard to believe!