What’s an evap line?
Evap lines, or evaporation lines, are a fairly common phenomenon that can happen on any kind of urine pregnancy test that isn’t digital. They occur after urine dries, leaving a faint (or not so faint) line behind that can be misinterpreted. What I didn’t realize was that an evap line can look exactly like a positive test result.
How does an evap line happen?
Pregnancy tests are basically tiny chemistry experiments you run on your bathroom counter. Urine travels across a test strip where it has a chance to interact with chemicals that will signal if hCG is present. The tricky part, aside from not peeing on your fingers while you’re doing it, is that you can’t always control for every variable, like for example tiny variances in the individual test strips, or how the urine dries on the paper. Evap lines can form when the ink used to signal a positive…