The Making of a Tennis Ball continues with the layer everyone actually touches: the felt.
The rubber core gives the ball its bounce, but the felt is what gives it a game. Without that fuzzy outer layer, a tennis ball would behave more like a squash ball or a bouncy toy — fast, slick, and almost impossible to control with any nuance. Felt is what lets a player generate spin, slows the ball down just enough through the air, and gives it that distinctive, slightly muted sound off the strings.
A Late Addition
Felt wasn’t part of the ball from the start. Early rubber balls were played bare, or wrapped in cloth strips sewn by hand — a solution that worked well enough on grass but wore through quickly and behaved unpredictably. As the game moved onto harder, more abrasive surfaces, manufacturers needed a covering that could take that wear without shredding apart mid-match. Machine-applied felt, glued and stitched around the rubber core, became the standard by the early twentieth century, and the sport has never gone back.
What’s Actually on the Ball
Modern tennis felt is typically a wool-nylon blend — usually somewhere around 55–60% wool, with the remainder synthetic fibre for durability and shape retention. Pure wool alone tends to flatten and mat too quickly under repeated impact; the synthetic blend helps the felt keep its nap, and with it, the ball’s ability to grip a string bed and hold spin.
Most of that felt is cut from cloth woven in a small number of specialist mills — Thailand is one of the main sources for the raw material used by major manufacturers today — before being die-cut into the two dumbbell-shaped panels that wrap around the rubber core. Those two pieces of felt, glued and pressed on by machine, are what turn a rubber shell into the ball you actually recognise.
Next in the series: The Pressurisation.
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