There have been several other discussions on threads here with regards to this pen. It is always advisable to test any product on scrap fabric the same as your project. This includes having the scrap fabric pre-washed and treated the same manner as the quilt. The advisement says that the marks go away with heat, but some have reported that they can reappear when cold or moisture is applied. It is not certain at this point whether washing with soap and water will fully remove the ink from the fabric. So always pre-test on your project.
Pam M