How flat is a granite worktop?

[graffian]

I remember seeing a mate checking his surface plate, not sure why he had a surface plate as he painted cars;-) he had plotted the surface out into squares and was checking between squares by resting a spirit level across a pair of cylinders placed in two squares.

I gather gravestones, surface plates and worktops are all finished on the same machinery. I asked in a stomnemason and they said they often had a skip full of bit's, I keep meaning to call back and get some bit's.

I would look into suface tension, if you could get a bit of plate glass and seperate the plate glass and surface plate at one end with a feeler gauge the surface tension of a thin liquid would show as a straight line, if the surface was flat.