crystal clear poas test evap line?

[STARRYSKY]

okay- I used a crystal clear mid stream test - not fmu but not really diluted either, thought I could see a really faint line, but in no way vis from arms length or by just glancing, was thinking it was just my imagination.
about half an hour to an hour later there is a definate line there, still faint but there, is blue, has colour.
just wondering if anyone has had false positive or evap lines with these tests?