Now see that is where you are going to send people down a silly path (not serious stuff like we're talking about). A beer mug, or anything made of smooth glass, will not work to sharpen steel. A coffee mug works because it is unglazed ceramic on the bottom, a material both rough and much harder than steel.
So to all you guys out there busily dragging your swords across a beer mug (yeah, that sounds like a euphemism....), it ain't gonna' work no matter how much fun you are having doing it.
Brian
I can see Jim sharpening his sword with a beer mug maybe but not his wife's imaginary car window.