How do i know when the clear coat is off?

I'm going to sand my car to primer it, how do i know when i have taken the clear coat off?How do i know when the clear coat is off?
as you sand the clear coat dust will come off as white once you go thru the clear the dust will be the color of the base coat beneath also once you burn thru the clear if you blow off the surface you will actually be able to see the clear ';edge'; as you pull it back from the color.





It's really not neccasary to remove the clear unless it's damaged,cracked,peeling something like thatHow do i know when the clear coat is off?
Sandpaper will most definitely remove the clear coat. There will be no question about it. Get yourself a dual action sander, a board sander, and a lot of 180 grit paper disks and a continuous roll. You will have the clear coat off in a couple of hours.
When you get to the level where you see a chalky surface, or you see the metal period.