A tennis ball may look like nothing more than a football to you and me, but it’s actually a much more complex ball. It needs to meet certain specs across a wide range of criteria. When it comes to making a tennis ball, manufacturers have a number of options. They can use the same basic material for every ball and make a batch based on that standard, or they can introduce different tooling and new processes in an effort to make each ball more consistent.
In this article, we’ll reveal the inner workings of one of the most complex soccer balls in the world: The tennis ball.
There are many types of the natural rubber and synthetic rubbers used in the making of tennis balls. The rubber used in tennis balls is a mixture of chemicals that are mixed and passed through rollers until it comes out in a certain way. The rubber is then pressed into pellets which will then make up the ball’s shape.
Half Shells
The half-spheres are melted by a high temperature molding machine. The rubber pellets are put into the mold and heated up to around 155°C. They are then machine-pressed at a pressure of approximately 160 kg/cm2 into a perfect half-sphere and an adhesive is added to each edge to secure the balls in place during their travel through the pipe.
Vulcanization
The vulcanization, or “vulcanization”, stage of the process involves heating the two halves together in a hydraulic press. The balls have been loaded into the press and then joined using heat and pressure, forming an unbreakable connection. Just before they come together, the pressurized air is added which conforms to the correct pressure as laid out by the ITF. This is known as the core.
Sanding
The sanding step is where the soft cover of a tennis ball is created. It’s a long, slow process that uses sandpaper and heated glue to create the furry surface of the ball.
Covering the Ball
A covering is the exterior surface of a tennis ball. Felt is cut into the shapes, known in the trade as ‘dog bones’, covered in glue and each ball is then wrapped in two pieces of material either by machine or by hand. The first step is to roll the felt up tight in a suitable sausage form and then stretch it out with your hands until it can be formed into its final shape before gluing on the cover.
Finally Ready to Use
Whether they’re being made in your local factory or by a small family-owned company in Lapland, tennis balls are made to the exact same specifications. The raw material used is polyurethane, which after being mixed and compressed is vulcanized into rubber with a polymer called polyvinyl acetate. Once this high-strength material is heated, air bubbles bond the two surfaces together. The balls go through the usual process of quality control before packing them into pressurized cans ready to be used.