Evaporation lines are caused by evaporation of the urine in the result window of a pregnancy test. These are lines that shows in the result window of the test. An evaporation line develops when the urine on the test area begins to dry, leaving a faint, colorless line. Evaporation lines appear as a result of the composition of the particular urine specimen - and they may appear on any test regardless of brand. short length mother of the bride or groom collections