how can you tell when a waterblock it smooth enough?

[all420]

I am working on my new watercooling setup. Right now I am lapping my waterblocks. I am using 2000 grit sandpaper. How do I tell when they are lapped enough? I know that it should have somewhat of a mirror-like finish, but when is it time to stop lapping? THanks in advance.

[Krusty]

Generally, when you start out, some spots will get sanded down while others aren't because the surface is uneven. With my DD maze2, the center was teh last part to start getting sanded because the edges were raised a bit.

What I did was sand until I didn't see any tiny scratches in the center of the block any more.