Everything to know about a tennis ball
If you want to know everything about the tennis ball, you need to start with the history of tennis, which has been around in one form or another for centuries.
Tennis has its roots reaching back to the 1200s in France, where it was played by monks in cloister using their hands. This early game was called jeu de paume, or simply, the palm game.
It wasn’t until the 16th century that tennis players began using rackets, and the game began to more closely resemble modern tennis. This new incarnation was called Real, or Royal tennis, and it was played almost exclusively by the aristocracy in England and France. Many of the original tennis courts from that era remain today, although they are all primarily in England. The old courts in France were destroyed or decommissioned in the violence of the French Revolution.
By the 1870s, the game of lawn tennis had developed and grown into the game we play today. Of course, as the game developed, so did the ball, and by the 1900s, the evolution of the tennis ball was well underway.
What was the first tennis ball made out of?
To you or me, early tennis ball materials would seem strange, unpleasant, or even downright disgusting. Some of the earliest examples of tennis balls found in Scotland were made with wool and the stomach of a sheep, and wrapped with rope. Other early Scottish versions were found made using animal fur, rope made from intestine, and even pine wood. The strangest examples of old tennis balls have to be when workers in 1920’s England found balls that contained putty and human hair stuck in the roof beams of Westminster Hall during a renovation.
The history of the tennis ball hasn’t always involved strange materials, though. Later versions were made of leather and filled with more common things like chalk, sand, sawdust, or even earth, until the king of France at the time, Louis IX, tried to standardize the game, claiming that only tennis balls made of good leather and wool were acceptable.
It wasn’t until the 1870s and the advent of lawn tennis, that the tennis ball as we know it began to take shape aided by the development of the vulcanization process for rubber. Although the earliest rubber tennis balls were solid and uncovered, it wasn’t long before they were hollowed, pressurized with air and stitched into a flannel covering to decrease wear and improve play.
Eventually, something matching the felt-covered ball you would recognize today began to take shape.
What are tennis balls made of now?
The easy answer is that tennis balls are made of a international tennis federation or shell, a felt or wool cover, and a cement glue that holds the two together.
The harder answer is that the exact recipe for the modern tennis ball is a closely guarded secret, and each manufacturer may have several different types of ball in their range, each with a different specification.
While the materials in each tennis ball can differ, the main components are generally very similar. The tennis ball shells themselves are made from natural or synthetic rubber or, usually, a blend of both. The same goes for the felt - most tennis balls are covered in felt of either wool, nylon or a mix both.
To provide you with some examples, according to Wilson which also manufacturers rackets like the Wilson Clash, their US Open tennis ball is made from a rubber compound that is 2/3 natural rubber from Thailand and 1/3 synthetic. The felt, or tennis ball fuzz, on a Wilson ball, is also primarily wool, with a blend of 30 per cent nylon.
Penn, another well-known manufacturer, is a little more secretive when it comes to their composition, but they do refer to New Zealand wool and natural rubber in some of their product descriptions.
Finally, Slazenger, the tennis ball sponsor for Wimbledon, uses Malaysian rubber in its balls but makes very little and has its rubber shipped in from New Zealand.
What is inside a tennis ball?
This is kind of a trick question because there are two main types of ball - Pressurized and Pressureless tennis balls, and they are made very differently. Pressurized balls are hollow and have nothing inside them but air or gas. Pressureless tennis balls have a solid rubber ball core.
What is a pressurized tennis ball?
To make a pressurized tennis ball, companies fill the rubber balls, or rubber shells, with either compressed air, nitrogen, or a mix of both.
The reason for the nitrogen or nitrogen/air mix is that nitrogen is a denser gas and does not escape through the tennis ball’s rubber core as easily as oxygen or air does, allowing the ball to stay fresh or responsive longer.
There is a common urban myth that the gas inside a new tennis ball will kill you if you inhale it. Still, there is no real scientific evidence to back it up, and neither nitrogen nor oxygen is toxic to humans (or dogs!) unless they are highly concentrated. Even if it were true, only new balls would be dangerous, and even then, not for long.
What is a pressureless tennis ball?
A pressureless tennis ball is exactly what it sounds like. While pressurized tennis balls depend on the pressure of the gas inside their shell to allow them to bounce when you hit them or when they hit the ground, the non-pressurized version usually contains a solid rubber core that is harder than the external shell.
According to the ITF (The International Tennis Federation) and USTA (United States Tennis Association), for use in tournament play, pressureless balls must have an internal pressure rating of less than 1 psi (pound per square inch).
What’s the difference between pressurized and pressureless tennis balls?
The key difference between the two types of tennis balls is how they perform and how long they last.
Pressureless, or more correctly, non-pressurized tennis balls have a solid core that allows the ball to bounce properly without going flat as the gas inside escapes through the rubber. In contrast, pressurized tennis balls start to go flat immediately after the tennis ball can is opened; non-pressurized balls keep their bounce much longer and can be used to play or practice tennis as long as their felt cover holds up.
In fact, as you wear the felt down through play, pressureless tennis balls get faster.
Why are tennis ball cans pressurized?
Everybody loves that sound you hear when you open a new can of tennis balls, but did you ever wonder why it does that?
Manufacturers pressurize tennis ball cans because when hollow tennis balls leave the factory, they have been pressurized to around 12 psi (pounds per square inch) higher than the normal outside air pressure at sea level, which is about 14.7 psi. If you add those two figures together, that puts the pressure inside each ball at 26.7 psi, nearly twice as high as the pressure of the air around it.
From the moment you open a tennis ball can, the balls that are inside it begin to steadily lose their pressure. They continue to do so until the pressure inside the ball is the same as that of the air around it.
To make sure their balls are not dead, or flat, when you finally take them to the court, manufacturers match the pressure inside the can to that inside the balls, guaranteeing the balls are always fresh when the can is opened.
How many tennis balls does a tournament use?
You would be surprised.
A Grand Slam tennis tournament uses a huge number of new balls to make sure the players are always playing under the best conditions.
For Wimbledon in 2020, Slazenger provided 54,250 tennis balls. That is enough to make sure the center and number 1 court each have 48 tins of balls on hand for players for each day. Slazenger also stocks the side, practice courts with 24 tins, each, per day.
If this seems excessive to you, Wilson supplied 70,000 new tennis balls to the US Open, while the Australian Open used a modest 48,000 balls provided by Dunlop.
The Australian Open website breaks down the number of Dunlop balls at the Australian Open like this:
- Six new balls are used for the five-minute warm-up and the first seven games
- Six new balls for every nine games after.
How much does a tennis ball weigh?
How much a tennis ball weighs depends mostly on its purpose.
Tournament balls are usually lighter than heavy-duty practice balls, but the weight difference is generally within a very tight range. According to the ITF, a ball suitable for competition play, the ball must weigh between 1.975 and 2.095 ounces if you speak metric that is 56.0 to 59.4 grams.
What is the circumference of a tennis ball?
Official-sized tennis balls have a circumference of about 8.258 inches or 20.975 centimeters, but manufacturers and the ITF and USTA size their balls by width or diameter.
How big is a tennis ball?
When tennis ball manufacturers talk about the size of their balls, they measure their diameter. Most tennis balls 2.630 inches or 6.6802 cm across, although the ITF and the USTA (who generally follow the ITF’s lead) allow balls as small as 2.575 inches (6.5405 cm) and as large as 2.7 (6.858) inches.
Another issue with giving a definitive ball size is that in recent years the ITF, USTA, and ball manufacturers have been promoting slow balls to improve the experience of new players and get more people into the game. Slow balls can be up to six percent larger in diameter than their competition-oriented counterparts.
Why is there fuzz on a tennis ball?
The fuzz on a tennis ball, or felt, (I have even heard it called hair) panels on a tennis ball are there to protect the rubber shell from wear and to control ball aerodynamics and the way the ball bounces. Each ball has two interlocking panels glued to its core, which are often called dog bones because of their shape.
In terms of tennis ball aerodynamics, the felt makes the movement of the ball more predictable by slowing it down and providing a bounce that stays uniform, even on different playing surfaces. The felt also allows the racket strings to get a far better purchase or grip on the ball than a smooth rubber surface would.
Felt also helps with aerodynamic drag, which means that the ball travels as a player expects, and it bounces off the different surfaces predictably. Even though certain surfaces affect the ball in different ways, the unpredictability is not as crazy as a ball without felt would be.
The fuzziness also determines how fast the ball goes, both on the court and in the air. A very fuzzy ball will have a slower, much more predictable bounce, especially if the felt fibers are fluffed up. This is why when you watch the pros, they look at a few different balls before they decide which one to serve. They are looking for a ball that still has a tight, even weave because it will serve and bounce faster, giving them a small advantage over a more worn, fluffy ball.
Are there different kinds of tennis balls?
Buying tennis balls is not as easy as you might think.
There are many kinds of ball types you can choose from other than the normal tournament or competition fare. There are even specific types of tennis balls that you may want to use in personal tennis ball machine.
Tennis balls come in up to four different speeds, can have three different grades of fuzz, and can be pressurized or non-pressurized. There are also tennis balls designed for hard court, clay, grass, and sand tennis courts, and even different levels of competition and ground elevation such as heavy-duty, high elevation, and championship. When buying a tennis ball just make sure you know what type of tennis court you will be playing on before.
Why are tennis balls yellow?
No discussion about tennis balls would be complete without talking about why tennis balls are yellow.
While they do come in a variety of colors, anyone under the age of 50, has a mental image of the ubiquitous yellow tennis ball when the topic comes up.
But, tennis balls were not always yellow, in fact, until 1972, they were usually white, and, sometimes, even black.
The man responsible for the color change is David Attenborough (yes, that David Attenborough), who at the time was the controller of BBC2, the television channel that broadcasts Wimbledon in the UK. Attenborough conducted a study that demonstrated the yellow ball was far easier for viewers with color televisions to see, especially when the ball was near the white court lines.
The ITF was quick to amend their rules to allow a white or yellow ball, but despite the 1972 rule change, Wimbledon held out, using white balls until 1986.