In curling, does scrubbing the ice speed the stone up or slow it down?

Sweeping (the correct term for scrubbing) is done for 2 main reasons in curling.

Reason 1: To speed up the rock (or drag the rock further along the ice). This is done because at the start of each game there are ice technicians that will pebble the ice. Pebbling is sprinkling water on the ice, this is done for the rocks to curl and prevent an smooth ice surface. Unlike other ice sports; smooth ice is not the ice condition you want. Like the others have stated; sweeping causes friction and will melt the ice which creates less resistance for the rock so it can move farther down the ice.

Reason 2: To hold the line of the rock. If you watch curling, they will get the 2 people to sweep the rock because "the line is tight". By sweeping the rock and the less resistance the sweepers are able to hold the rock from curling as much by sweeping.

Often near the end of the game you may hear people saying the ice is flat. This is when the peeble is gone and you have the smooth ice. It's hard to call a shot and hold a rock when the ice is like this.

Pebbling Curling Ice

in the "sport" curling, scrubing the ice causes friction which melts the ice a bit. the melting of the ice smoothens the area in front of the puck. the faster the sweeping, the more friction to smooth the path out. notice they adjust the speed in which they sweep the path nearing the end... the puck slows due to the unhindered, rougher ice when they slow.

It definitely won't slow it down since it's just water, but drnking 8 cups of water a day will help speed up your metabolism so I guess eating ice can't hurt :P

It speeds it up. They are sweeping the little ice shards out of the way. It also affects they curvature of the stone.

They say it speend it up by buffing the ice.