I had blocks that was done by my late Sister, and I made 3 quilts out of them...after I got them put together for the tops, I washed them and all the markings came out...she had done these about 12-15 years before...so I was really wondering if the blue X's would come out after that length of time...and they did...so I think you will be safe in washing the top, before you sandwich the quilt...good luck...