An evap is a faint ghost like line with no colour on a hpt where the positive should be...but its not a positive result..It happens because moisture or dryness make the strips antibody strip more visible...or as the test dries
They can look dent like, and even appear to have colour, but usually appear after the time frame eg. 10 mins Thats why you shouldnt look at the test after even if it turns 'positive'
Warning aswell: Any plus or minus tests may turn positive after the time frame, because the dye from minus strip leaks onto the vertical strip...
see
www.peeonastick.com
its brilliant!
Dont worry, your not being thick! I had never heard of them before!

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