Why Do Tennis Balls Have Lines?

Why do tennis balls have lines

During the tennis ball manufacturing process, the rubber sheet is cut into strips which are then processed further to create a series of round balls. The concentric circles and lines on the ball serve as quality control indicators to make sure all balls are made to exactly the same size.

This ensures all tennis balls are uniform in size and weight, providing consistent bounce performance for players across different skill levels. If there were no lines or circles, you would still have an orange-sized ball but it would be longer from end to end than a standard ball – not ideal!

Why do they smell so bad?

Since tennis balls don’t really get used that much after their first hit; we assume this stench comes from the factory process where they are moulded together.

Are some balls better than others?

Tennis ball manufacturers put a lot of effort into creating different ball types for different surfaces, levels and conditions e.g. indoor vs outdoor, clay vs hard courts etc. They’re all pretty much the same in terms of bounce performance but there are minor differences between them; which is why you have varying price ranges depending on quality and type. For example, the Wilson US Open balls that Serena Williams uses are designed to play at high speed on hardcourts – not ideal for your second serve during netball!

How exactly do they make tennis balls? (The science bit)

We know what you’re thinking – ‘I feel dirty even asking this question! But not to worry, we’re going to try and keep it as squeaky clean as possible so feel free to read on.

The tennis ball has two main parts: the rubber (the white part) and the felt tape (the yellow part). The rubber is made from a high-quality energy absorbing material called ethylene propylene diene monomer. This goes through a process of mixing, moulding, pressing and texturing before being cut and shaped by an injection machine into 20 identical balls.  The felt layer is composed of around 70% wool fibres which helps give structure and integrity to the balls. Once again, both layers go through extensive processing before they are ready for sale.

So how did they come up with the idea for tennis balls in the first place? 

This is what all of us curious minds want to know. The original ball used in tennis was a hard wooden ball that you may have seen our colonial forefathers using. The problem with using a hard wooden ball was that it didn’t bounce very well so, in 1859, British inventors Mcguffog and Ross patented the rubber-cored ball after observing how street urchins bounced around their handball out of old gutta-percha tree sap (Ethylene Propylene Diene Monomer) found on an island off the coast of Singapore.

Gutta Percha trees only grew on this island so by harvesting them they were able to produce an abundance of rubber which allowed the invention of balls that could bounce and not break.

Benefits Of Lines On A Tennis Ball:

Quality Control:

This was mentioned earlier, but every time a tennis ball is made it has to be checked and signed off by the factory inspector. The concentric circles on each ball are used as a reference point for checking size as well as the quality of manufacture. These lines can also help identify if there’s something wrong with your tennis balls; because you wouldn’t want them rolling around the court looking dazed and confused!


Without lines or circles, the surface of an orange-sized tennis ball would have to be smaller than a standard-sized one; therefore losing structural integrity. This could result in a weaker after-bounce performance which isn’t ideal for players that use their second-serve at netball training (like Serena Williams)

The Future of Tennis:

Some modern tennis balls are now made even squishier to help players play higher overheads. But this doesn’t come without a cost as many are complaining that the ball can be unpredictable and hard to control. This may explain why we haven’t seen any netball players on Wimbledon’s main court!  The US Open uses a harder ball than the Australian Open, further evidence that there are still developments to be made.

The Netballer’s View:

We can’t really say much except we’ve always been sceptical about using tennis balls in netball because they keep falling out of our hands! What we do know is that without these regulation lines and circles on tennis balls, it would be difficult to manoeuvre with them when shooting from close range (during passes and interceptions).

But if you’re playing doubles, then you’ll probably appreciate being able to hit shots over your opponents’ heads.

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