Tennis balls are made of a high-bouncing rubber core encased in a layer of fuzz. The fuzz is what makes the ball bounce so well, but it also makes the ball more likely to get dirty and deteriorate faster.

The fuzziness is created by applying a chemical treatment to the surface of the ball, then brushing it with steel wool or sandpaper to create small “fluff” particles. These fluff particles give the ball its unique texture and appearance, which helps it bounce so well when struck by a racquet.

The purpose of this treatment is to increase the coefficient of restitution (COR), which is a measure of how much energy is returned to the ball after collision with another object. COR can be increased by increasing elasticity or reducing elasticity (but not beyond zero). Increasing elasticity means that if you hit a tennis ball with enough force, it will bounce back almost as high as it was originally thrown up into the air — even if you hit it while standing still on flat ground!

Last modified: November 27, 2022