Yesterday I read a few posts where women were saying they weren't sure what an evap line was. I too was a little unsure so I found this on line which I thought explained it nicely. Also clears up why you shouldn't read results after the allotted time. Reading the results before or after the time slot given, can leave evaporation lines, which in themselves are faint or pale in color. It can look like a faint positive, but its really just the result of the urine evaporating and leaving a residue behind.