These silver marking pens changed my bagmaking life. I was using sharpies and ballpoint pens to write on the wrong side of my vinyls but now, I can write on the right side and wipe it off right after! Meant to be used on non porous surfaces. Do not let the ink sit on the material overnight, it may make it harder to remove.
I personally use water-based, fragrance-free baby wipes and have never had any problems removing marks. Please spot test on a scrap before using in your projects.
