The brush in curling is used to sweep the ice in front of a moving stone, reducing friction so the stone travels farther and straighter. Sweeping generates heat that briefly melts the textured surface of the ice, creating a thin film of water that acts like a lubricant under the stone. This gives curlers real-time control over where the stone ends up after it’s already been released.
How Sweeping Changes the Ice
Curling ice isn’t smooth. Before a game, tiny water droplets are sprayed onto the surface to create a texture of small bumps called “pebble.” When a stone slides over this pebbled surface, the bumps create friction that slows it down and causes it to curve, or “curl,” to one side.
When sweepers vigorously rub the brush back and forth in front of the stone, the friction between the brush pad and the ice generates enough heat to briefly melt the tops of those pebbles. That thin layer of water reduces the friction between the stone and the ice. The result: the stone keeps more of its speed and doesn’t curl as much. It travels farther on a straighter path than it would if left alone.
Why Downward Pressure Matters Most
Effective sweeping isn’t just about moving the brush quickly. Research on elite curlers shows that the force you push down into the ice matters more than how fast you move the brush side to side. Elite male curlers apply roughly 630 newtons of downward force (about 140 pounds of pressure), while elite female athletes average around 400 newtons. Beginners apply significantly less. That difference in pressure directly translates to how far the stone travels, because harder pressure generates more heat and melts the pebble surface more effectively.
Sweeping speed still plays a role. Elite male curlers sweep at about 4.3 strokes per second, and elite women at about 3.8 strokes per second. But studies comparing the two factors found that consistent, heavy downward pressure on the brush head contributed more to extending a stone’s distance than stroke speed alone. Positioning matters too: the closer the brush head is to the sweeper’s body, the more downward force they can apply.
Controlling Distance and Direction
Sweeping gives a curling team two levers of control after the stone leaves the thrower’s hand: how far the stone goes (called “weight”) and how much it curves (called “line”).
For weight, sweeping is straightforward. The more you sweep, the less friction the stone encounters, and the farther it slides before stopping. If a stone was thrown a little too lightly, aggressive sweeping can compensate by carrying it deeper into the house (the target area).
For line, sweeping keeps the stone on a straighter path. Every curling stone naturally curves as it slows down, and that curl becomes more dramatic near the end of its travel. Sweeping in front of the stone delays that curl, effectively widening or narrowing the stone’s arc depending on when the team starts and stops. While there’s limited scientific evidence on exactly how sweeping controls curl direction, it’s a core part of competitive strategy, and teams rely on it constantly.
How the Skip Calls the Shots
The skip (team captain) stands at the far end of the ice watching the stone approach and directs the sweepers with voice commands. A shout of “yes,” “sweep,” or “hurry” tells sweepers to get on the ice hard. “No,” “stop,” or “up” means back off. Sometimes the skip yells “line,” which tells the sweepers the concern is about the stone’s curl path, not its speed.
This communication is constant and urgent. The skip can see the stone’s trajectory relative to the target better than the sweepers can, so they act as the eyes while the sweepers provide the muscle. A well-timed call to sweep or stop sweeping can mean the difference between a stone landing perfectly on the button or sliding through the house entirely.
Brush Equipment and Regulations
Modern curling brushes have a long handle with a padded head covered in synthetic fabric. The brush head presses flat against the ice, and sweepers push it back and forth in the stone’s path. Older brushes used corn straw or horsehair bristles, but synthetic pads became the standard because they’re more consistent and durable.
Brush technology became a controversy in 2016 when certain fabric and foam combinations were found to give teams an unfair advantage by altering the ice surface too aggressively. This led to what curlers call “broomgate,” prompting the World Curling Federation to establish equipment standards and an approval process for brush heads. Those regulations continue to evolve. For the 2025-2026 season, the federation updated its rules to require softer foam in brush heads, restricting firmer foams that could manipulate the ice too much. Traditional brushes with fabric stapled directly to the head remain approved.
The goal of these rules is to keep sweeping as a test of athleticism and teamwork rather than a technology race. The brush should help a team execute its strategy through physical effort, not through engineered materials that do the work for them.