I teach quilting and in the beginner class when we go over washing material we do not recommend that you even use the dryer sheets. Have you ever washed a dark t-shirt and then dried it with a dryer sheet and ended up with spots that look like grease. (they don't come out) I use to have that problem and thought we were sloppy eaters. It is from the dryer sheets, because they have a petroleum base. That is what gets on your t-shirts/material.