Sweeping & the Science of the Brush

How can two people with brooms change where a heavy granite stone finishes? The answer is friction — and for one strange season, the answer got out of hand.

What a brush actually does

A curling sheet is sprayed with water that freezes into bumps called pebble; the stone rides on those peaks. Brushing just ahead of a moving stone melts the tips, cutting friction so the stone runs farther and curls less.

When fabric became a weapon

In 2014-16, stiff, abrasive ‘directional’ fabrics scratched a grain into the pebble that a sweeper could aim — effectively steering the stone. That is the technology behind Broomgate.

Settling it with science

At the 2016 Sweeping Summit, National Research Council scientists tested brushes with throwing robots and GPS, then standardised a single certified fabric for everyone.