I've never been able to remove iron on transfers. Don't think they were meant to be removed. My stitching always covered the lines. The pre-stamped embroidery pieces (baby quilts) I bought will come out with water.

Arizona sunshine took mine off...before I was finished!!!

Bottle the Arizona sunshine and make a fortune. Sorry couldn't resist it. No idea personally howto remove unless you do a quilt stitch same colour.

It was one of the reasons I loved counted cross stitch when I first learned about it when I was in college--no blue lines!