Okay, on my test, I had a kit that was prepped with matte varnish real thin before painting. I had drawn on a hair line with a dark prisma pencil about 6 months ago. The dishsoap took some of it off but not all of it, in other words, it lightened it but didn't remove it all. BUT-this makes me think we do need to seal them so that is what I will be doing from now on.