Have you ever noticed that whenever you go to the store to buy tennis balls, you see a pack of three balls in a sealed container? What makes this happen? Ever wondered why? What difference do sealed-can balls and ordinary balls have? If yes, then here is your answer.
The answer to your question is that a tennis ball is packaged in an airtight can to maintain the proper inside pressure required for it to bounce properly. Tennis balls are filled with pressurized air, so they are packaged in cans.
Because of the mismatch between inside and outside air pressures in a can, the balls begin to diffuse air when you open the can. The airtight cans provide protection against gas leaks as well as a proper bounce when the balls are used for the first time on the courts.
The air inside a pressurized tennis ball weighs 27.7 pounds per square inch (although some balls may be considerably less pressurized). This design eliminates weight and increases bounce on inflated tennis balls.
A tennis ball’s air pressure falls when the internal pressure is lowered by this large pressure difference, lowering bounce and decreasing air pressure. With each ball you strike, more leaks are created.
When a match is about to start, the airtight sealed cans of pressurized tennis balls are broken open and taken out. Fresh balls have the necessary bounce and are lively. To maintain the technical specifications for air pressure and bounce, tennis balls should be kept in an airtight container from the time of production until the start of the match.
There is some air expelled from tennis balls due to the pressure inside each ball. The pounding action of the balls caused them to release microscopic amounts of air. The ball is prone to losing a great deal of air as time goes on, so the pressure does not remain constant.
Consequently, it loses speed and bounce. So now it’s time to toss the ball out, and/or give it a different purpose.
How to pressurize a tennis ball?
- Tennis balls are manufactured first by producing the rubber shell. Rubber trees in Thailand provide the material for Wilson balls. Thin, heat and cut sections of rubber compound are required.
- Molding half-shells from the rubber compound is completed after the rubber compound has been cut. To solidify the shell, the molds are subjected to high temperatures and pressures.
- Each assembly is stitched together with an adhesive layer.
- A hydraulic press is used to pressurize ambient air to 18 psi while half-shells are placed in it. The pressured air inside the tennis ball is trapped as the shells are combined into the core.
- To prevent the core from exploding, the shells are cooled to about 127°F after the adhesive has cured. Within 15 psi, the internal pressure of the core is reached.
- The internal pressure of the can will be 12 to 14 psi when the balls are ready to go in. The air is pumped into the cans at two psi more than it’s put into the balls because the cans contain more air.
In summary, tennis balls are packaged in sealed cans so their internal pressure will remain constant. The balls begin to lose their air once you take them out. You won’t become a high-level tennis player by studying this information, but you might save money over time.
Tennis balls should not be opened unless you will be actively hitting the balls for a few weeks. Maintaining the bounce longer will hopefully save you money on new balls.