It makes a clear, bright line on the fabric, and after a while the color fades away on it's own. I started out with chalky-pencils, but those are a bit of a pain; the tips don't fit neatly in the slots of my templates and end up wearing down strangely. Not this tidy little pen! In the photo below, I've drawn a line on some turquoise fabric. Look at how clear the line is!
I first used the pen on Quilt 2 (the Ohio Star quilt). That was over a year ago, and only now is it running out of "juice"!