QUESTION:Why are tennis balls stored in a pressurized can

ANSWER:  The air inside a tennis ball is slightly higher than normal atmospheric pressure or what we might call outside pressure. If tennis balls were stored out in the open, not in a pressurized can, some of the air would slowly leak out, especially over a period of months or years.  You would have a less lively ball.

By storing the tennis ball in a pressurized can, the air outside the ball is higher than the air pressure in the ball. This prevents air from leaking from the ball.

Once the ball is out of the can, the leakage can be kept to a minimum by storing the ball in a freezer. This reduces the pressure of the air inside the ball and lessens the leakage rate.

A few minutes out of the freezer, the air inside the ball warms up, increases  the pressure, and you have a normal ball.

Sometimes people think that tennis balls are vacuum packed. Simply not true and it would be counterproductive. If tennis balls were vacuum packed, the air would leak out of the ball rather quickly, in a matter of hours. Instead, the air is sort of packed into  the can, rather than taken out.

A pressurized metal tube that held three balls with a church key on the top was introduced in 1926. A plastic can with a full-top pull-tab seal and plastic lid to hold three or four balls per can was brought out in the early 1980’s.

Why is a tennis ball fuzzy? That fuzzy felt covering increases air resistance and reduces the speed of the ball through the air. It also reduces the bounce. A fuzzy tennis ball is easier to control. A bald tennis ball has more speed, more bounce, more spin, and is harder to control.

A tennis ball is tested for bounce by dropping it from 100 inches onto concrete. A bounce of 53-58 inches is acceptable, based on sea level and standard temperature and humidity conditions.

Most tennis balls are fluorescent yellow, known as optic yellow. People describe them as a greenish- yellow color. They were introduced in the early 1970’s. It made them easier to see and more visible on color television.

The most common use for an old tennis ball is to cut a hole in the ball and attach the ball to the bottom of chairs in schools and nursing homes. This technique reduces noise and prevents scuffing or scraping the floor.

Wimbledon tennis balls are recycled by becoming a home for the Eurasian field mouse.