I've been using pregmate strips for ovulation and pregnancy tests for the last 3 years. I never had any issues with faint positives evaps or indents during that time. However, the last week I've had my usual Stark white negative tests followed by what I thought was a faint line and now I'm thinking it might have been an evaporation line. But wouldn't all the tests get the same evap line? Like when all my other tests dried there is nothing on them...just white...but on the one i took this morning it dried with a faint pink line. Can someone explain the science behind this? Basically im asking why do some dry with a faint pink line and some dry plain white. All from same box same batch same type of test.