Getting rid of lines on a quilt

I'm not sure if this is a skill or task per se but I was wondering if anyone knows how to get rid of  the guide lines on a quilt.  I have a lovely quilt from my grandmother that she appliqued and hand quilted but the lines from the pattern are still there.  The quilt is probably 20 years old so I imagine the lines are pretty well on there -- any suggestions?

If the quilt is in good repair (no rotting threads, worn spots or holes) you can machine wash on delicate (if it will fit in your machine) with a little ivory dish soap or purchase a special quilt wash.

If you do not want to put in the machine you can soak and rinse it in your bath tub.

Blot it dry with bath towels then hang or dry flat if you have the space.  After it is dry you can fluff it a little bit in the dryer on the "air" setting.

I am assuming the marks are from a regular lead pencil, if so they will come out after a couple washings.