I took an applique class from a nationally known instructor who cautioned to wash the quilt without detergent and softener after it was completely finished to be certain the marking ink was completely washed out. She told us about spritzing the marks away on several quilts (without washing them) to display at a trunk show/workshop ... but when she pulled them out to display, some of the ink had reappeared ... and some of it in places wjhere she hadn't marked! She assured us that one washing in water only made sure the ink stayed away forever - it had something to do with the humidity of where she lived compared to the humidity of the (second) place where she taught. She is still laughing about this, though, so clearly she's not worried any longer.