Hi Another potential newbie question, sorry I ordered a bag of the strips off Amazon and have been using them over the weekend. Friday I got a faint line, Saturday I got the control line only and on Sunday I got the faint line again. I know that these are all negative but why do you get a line sometimes and not other times? I've seen evap mentioned - is that what happens to no lines? I was rubbish at science at school so, true to form, I was probably not testing with a "controlled" substance i.e. I pee'd at the same time but when I got the no line I had left it "to get to room temperature" for a wee (lol) bit too long so I'm not sure if that affects them? Many thanks and I'm sorry if that question has been asked a million times before!