The U.S. Open is underway in New York, and once again I’m reminded that I should have practiced harder when I was a junior. But bygones! Let’s talk tennis balls. Specifically, the ones that come sealed in pop-top cans.
If you didn’t know, not all of them do. “There are two types of tennis ball: pressureless and pressurized,” says Rod Cross, a retired physics professor and an expert on the technology of tennis. (The name of one of his books is The Physics and Technology of Tennis.) It’s the pressurized ones that come in cans, and coming up, he’ll explain why.
But wait … footballs are pressurized, which just means that the air pressure inside the ball is higher than outside. So are basketballs. And volleyballs. And tons of other sports balls. But hardly any of them are sold in cans. To further the tennis-ball conundrum: “In the old days, when I was young, even pressurized balls were sold in cardboard boxes, [not cans],” Cross says.
It’s all too much for this weekend warrior. What happened in the tennis-ball-packaging world since the professor was a kid? The balls haven’t changed all that much. Ahead, Cross explains why tennis balls come in cans and lets us in on a few secrets of the science of tennis balls. Read on to learn more.
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How long have tennis balls come in cans?
It’s been nearly 100 years. When lawn tennis was established in the United States, starting around 1880, tennis balls were mostly sold in paper bags or cardboard boxes. In the late 1920s, the Pennsylvania Rubber Company, which later evolved into one of the biggest names in tennis, Penn, began selling tennis balls in sealed metal cans.
They came with a key that rolled back the top like a sardine can, and they could not be resealed. According to the International Tennis Hall of Fame, World War II’s metal shortages brought back cardboard for a while, and Cross remembers seeing them packed in boxes into the 1950s (the aforementioned “old days”).
Resealable lids came along in the 1950s and ’60s, and in 1972, pop-tops replaced the key. In the 1980s, companies switched to plastic cans.
So why do tennis balls come in sealed cans?
Sealed cans allow manufacturers to control the pressure precisely inside the can, keeping tennis balls at their peak performance level for as long as possible. Here’s why using a can works best.
It keeps them bouncy
Pressurized tennis balls bounce because the air inside the ball is at a higher pressure than the outside atmosphere. As the ball hits your racket or the court, the pressurized air inside pushes against the rubber and helps it resist deformation (aka getting squashed), and the ball bounces.
“Normal atmospheric pressure is 14.7 psi, but the pressure inside the ball is about 27 to 29 psi,” Cross says. So sealing the can and injecting air under pressure keeps the balls in the exact environment they need to properly bounce. You can test this: Regulation hard-court tennis balls (called Type 2 or medium) must bounce back to between 53 and 58 inches when dropped from a height of 100 inches.
It stops air from leaking out
“Pressurized balls are sold in a pressured can to prevent the air from gradually leaking out through the porous rubber wall,” Cross says. Tennis balls have a hollow rubber core that is not airtight, and once that rubber core is formed and covered with fuzz, that’s it—there’s no way to pump them up like you can a football or soccer ball.
This is why pressureless balls, which bounce due to their thicker, stiffer rubber instead of an air-pressure differential, are popular for practice and in ball machines. “Pressureless balls last longer, since the air doesn’t leak out,” Cross says.
It preserves shelf life
Sealed cans keep tennis balls fresher longer. Since a pressurized tennis ball loses air gradually, the old way of packing them in cardboard meant that by the time the balls arrived at the pro shop or sporting-goods store, they were already losing air and bounce. Players had to do a squeeze test to find good ones rather than have confidence that fresh balls were, well, fresh.
Today, that’s not a worry. Example: I have a few unopened cans of tennis balls in my garage. I bought a case months ago, and these are the stragglers. But I’m not worried in the least that they’ll be bad when I get to them. We’ll get to the specifics in the next section, but no matter how long it is, they’ll be infinitely more playable than if they had been sitting loose or in a cardboard box.
How long can they last in there?
The Penn balls in my garage don’t have expiration dates, and I can’t find any indication that Wilsons do either. (Wilson is another big name in tennis.) So I suppose they could last indefinitely. But most tennis pros put the window of freshness on an unopened can at anywhere from six months to a year, with two years being the outside limit.
But after you crack it open, the countdown begins. “Once opened, balls in pressurized cans can still be used a few weeks later,” Cross says. But you won’t catch a pro using a three-week-old ball at Wimbledon. Those are more for you and me hitting around on a Sunday morning. Even then, after a few hard-play sessions, you’re going to notice a difference in the feel of the ball.
“At amateur-competition level, new balls are used for each morning or afternoon event, while at professional level, new balls are used after every nine games,” Cross says. As the ball gets smacked around, the felt cover gets fluffy and slows down the ball as it flies through the air. “That’s why professionals take three balls to serve, then throw away the most fluffy ball,” he adds.
What is that “psssshhh” sound that you hear when you open a can of tennis balls?
That distinctive whoosh (which is always accompanied by that fresh tennis-ball smell) is the sound of the pressure being released from inside the can. As soon as you pop the top, the higher-pressure air inside the can rushes through the opening to the lower-pressure outside, creating sound waves that dissipate as the opening gets larger.
Can you revive a tennis ball?
Yes. It won’t make it as good as new, but depending on your standards, it might be close enough. “Old balls can be repressurized by placing them in a pressurized container for a few days, but the outer felt cover will still be fluffy or worn down,” Cross says.
You can find basic pressurizers for less than $20 at Target and Tennis Warehouse, and more sophisticated versions online for about $75 and up.
Do all tennis balls come in cans?
No. “Pressureless balls are sold in a cardboard box,” Cross says. Since the air inside them is at regular atmospheric pressure, there’s no need to keep them in a pressurized can. You can also buy pressureless tennis balls in mesh bags, especially if you purchase in bulk.
Pressureless tennis balls were patented by Swedish shoe giant Tretorn in 1955, and Cross says they’re popular in Europe and South America. But we’re seeing more of them over here too. Due to environmental concerns over the use of plastic in pressurized tennis ball cans, Wilson developed a new pressureless ball called Triniti that mimics the livelier bounce, faster play and lighter “feel” of pressurized balls. These are sold in recyclable cardboard boxes.
Do other balls come in cans?
Some do, but not many, and the reason is simple: “Other balls can be pumped up to the correct pressure with an air pump,” Cross says, though some balls don’t use air or pressure at all. Here’s how it breaks down.
- Padel balls: A very close cousin to the tennis ball, padel balls also have a hollow rubber core and a felt cover. They are sold under pressure in pop-top cans, but they are softer and have more give.
- Racquetballs: The hollow, air-filled racquetball gets its bounce from the rubber shell, not the air inside (much like a pressureless tennis ball). So while they are often sold in cans to keep the rubber fresh, the cans are not pressurized.
- Pickleballs: The nemesis of tennis players everywhere (I kid, pickleballers!), the plastic, Whiffle ball–like pickleball is hollow and has multiple holes, so it’s just sold in bags, boxes or other non-pressurized containers.
- Footballs, soccer balls and basketballs: Larger air-filled balls are sold naked or in boxes and are filled using a bicycle pump or air compressor. (If you’ve ever searched your garage and junk drawers for hours looking for the pump’s needle attachment, you feel my pain.) These balls will eventually deflate, but give them a quick pump and you’ll be good to go.
- Baseballs and golf balls: Solid-core balls do not have air inside at all, so there’s no need to sell or store them under pressure. They may get old and brittle, or lose performance capability after years of storage or use, but these balls won’t deflate.
Sources:
- Rod Cross, retired physics professor and author of The Physics and Technology of Tennis and Technical Tennis: Racquets, Strings, Balls, Courts, Spin and Bounce; email interview, Aug. 27, 2026
- Sports Engineering: “Dynamic properties of tennis balls”
- Wilson: “Wilson LABS: Triniti”
- Sports Technology: “Review of tennis ball aerodynamics”
- Head: “How to choose a tennis ball”
- International Tennis Federation: “2026 ITF Rules of Tennis”
- Penn Racquet: “A Century of Bounce, A Legacy of Performance”
- International Tennis Hall of Fame: “Tins, Cans & Cartons”
- Tennis Warehouse University: “Return Deformation of a Tennis Ball (Rod Cross)”
- Tretorn: “Our Heritage”
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