when the quilt is completely finished- quilted & bound- launder it- very good chance the pencil will wash out. I used pencil to mark quilts for 30+ years- never had one the pencil did not wash out of. I launder all of my quilts when they are finished- in the washer- with detergent- if I have anything I am concerned about coming out I give it a spritz of 'Shout' or 'Oxyclean spot cleaner. check to see the marks are gone before drying