If you don't want to try a razor blade, consider trying a plastic putty knife sort of thing. You can also pick up plastic razor blades at some auto parts stores. If you have a Menards home improvement store near you, both plastic putty knives & plastic razor blades are cheap there.
Frankly, I believe it would be difficult to harm porcelain with a regular metal putty knife or razor blade unless you whacked it with edge or corner of the putty knife. Porcelain is pretty hard and durable, but can get chipped if you ding it against something hard.
Topic: Story time! My first grail! Worth the read! (Read 4823 times)