If they're supposed to come off of hands, clothing and walls, they might work, right?
I colored a large circle of each color and just washed and dried it. Every bit of marker is gone.
I'm going to recolor them, and then iron it and re-wash to see if I get the same results.
Update: Here are the results after using the markers in each color to make a 1/2" dot, and then I ironed it good and hot! I also bought the Fabric fine line markers (permanent) and tested all those colors on the right. "Fine line" means 1/8" wide. This little scrap of fabric has been through the washer and dryer and again, all of the markings came out. Next time I need to mark a quilt for something I'm using the washable markers.