I don’t think the bottom of a mug is capable of enough precision to make the Sharpie trick worthwhile (or even (=flat) enough to talk about choosing bevel angles), but here is more info about knife sharpening than most people need :-)
It’s never going to give you as consistent an angle as a water stone is, certainly. But I’d still expect a difference if you tried to bevel one knife to 30 degrees and the next to 12.
I don’t think the bottom of a mug is capable of enough precision to make the Sharpie trick worthwhile (or even (=flat) enough to talk about choosing bevel angles), but here is more info about knife sharpening than most people need :-)
It’s never going to give you as consistent an angle as a water stone is, certainly. But I’d still expect a difference if you tried to bevel one knife to 30 degrees and the next to 12.
You may be right about the Sharpie trick.