Most of the test you add drops to the cylinder until the color becomes clear. but I've noticed that when the cylinder becomes clear, if you let it sit a couple of seconds after it becomes clear, the color will come back., and if you add another drop, it becomes clear and stays clear. So do you read it from the first time it becomes clear or the second?
I hope I'm making sense?! lol
I hope I'm making sense?! lol