Why You Have to Warm Up a Squash Ball: The Liquid Steam Physics Explained

A professional squash ball is literally dead weight until you hit it hard enough to turn the drop of liquid water hidden inside into pressurised steam.

If you drop a cold squash ball on the court, it will barely bounce an inch. Unlike tennis or basketballs, which rely on pre-inflated air pressure, a squash ball relies on thermal physics to come alive.

To make the ball play properly, players have to strike it hard against the walls for a few minutes before a match.

The Material Physics Behind the Bounce

The construction of a squash ball is a tiny engineering marvel designed specifically for high-intensity indoor play.

During a warm-up, the mechanical energy from repeated high-velocity impacts transfers directly into thermal energy inside the hollow chamber.

As the temperature reaches approximately 45°C (113°F), the liquid water inside undergoes a phase change, turning into gas. This rapid expansion increases the internal pressure of the ball, while simultaneously softening the surrounding synthetic rubber compound.

The result is a dynamic, fast-bouncing ball that responds predictably to precision shots.

If play slows down or stops for too long, the ball quickly cools, the steam condenses back into liquid water, and the ball returns to its inert, frozen state.

A professional squash ball is literally dead weight until you hit it hard enough to turn the drop of liquid water hidden inside it into steam.