The ice for curling is meticulously made and maintained. The ice sheet needs to be flat and level in all directions, then a “pebble” is applied. If curling ice were just plain ice, the stone would barely travel halfway across the “sheet”. And that’s assuming the curler is hurling it as hard as possible. Friction would halt the rock within seconds. So, to make the ice more amenable to the sport, ice makers employ a technique called “pebbling.” More or less what it sounds like, pebbling involves sprinkling small droplets of water across the playing surface between each match.
The curling stone’s concave bottom, which limits how much it comes into contact with the ice, and the pebbles reduce friction. Essentially, the pebbles melt a bit when the heavy stone runs across them, creating a micro-layer of water upon which the stone can glide.
The pebble maintains the “spin” (or curl) of the stone after it is released. Sweepers use their brooms to brush the pebbles, thereby reducing the friction further. Sweeping warms the pebbles, reducing friction and helping the stone travel farther and straighter. Naturally, the game changes slowly and subtlety as the pebbles erode, and the teams have to constantly compensate.
Learning how much a stone will curl during a game is crucial to being able to make different shots. In the left diagram the skip needs to understand how much the stone will curl so that he can direct the player delivering the stone where to aim and how hard to throw it.
In the second diagram, the Yellow team wants to deliver a stone onto the “button.” They could use a right-handed curl or left-handed. The choice will be based upon the knowledge of how the ice curls on the right or left side of the ice.