Why Do They Sweep? The Physics of Curling Explained

You’ve seen it on TV: one person slides a stone, and two others furiously scrub the ice in front of it while screaming “HURRY!” It looks chaotic, but it is actually one of the most precise displays of physics in sport.

Why do curlers sweep the ice?

Sweeping helps curlers control how far a stone travels and how much it curls as it moves down the ice. By changing the amount of friction beneath the stone, sweepers can influence both its speed and its direction.

1. The ice isn’t flat: it’s pebbled

Unlike the smooth ice used for hockey or figure skating, curling ice is sprinkled with tiny droplets of water that freeze into small bumps. This process is known as pebbling.

The curling stone travels across the tops of these tiny ice pebbles rather than sliding across a completely flat surface. This specialised surface is essential to the way the stone moves and curls.

2. Sweeping changes the friction

This is where the sweeping comes in.

When sweepers rapidly brush the ice in front of the stone using their synthetic brooms, they alter the surface and reduce the friction acting on the stone.

That means the stone loses less speed as it travels down the sheet.

3. Sweeping controls distance and direction

Reducing friction has two important effects on a curling stone:

• Distance: Sweeping can help the stone travel further before it comes to a stop.
• Direction: Sweeping generally helps the stone travel straighter and reduces the amount it curls.

So, when the Skip, or captain, yells “SWEEP!”, they will usually be asking the sweepers to help the stone travel further or prevent it from curling too quickly.

When you hear “WHOA!” or “OFF!”, the sweepers stop and allow the stone to continue naturally.

That constant communication is one of the reasons curling is such a tactical team sport. The player delivering the stone sets the initial speed and direction, but the sweepers can continue influencing the shot almost all the way down the ice.

The ultimate ice-free experience at The Curling Club

Enjoy all the competitive thrill of curling without the chill.

Our lanes are completely ice-free, meaning you don’t need specialist shoes or heavy equipment. Best of all, no sweeping is required.

We’ve removed the frantic cardio so you can focus entirely on your aim, strategy and the Alpine atmosphere.

Join us for the perfect winter social at our locations across London, including Vinegar Yard and Chelsea.