sharpening on glass...
try to take thin slices off the edge of the glass. The sand-blasted (frosted) edge of a plate glass shelf is even better. I have a 4"x1"x1/4" piece of plate glass w/ blasted edges I've had for 40+ yrs I picked up in Sydney, Aus.
U.S.C. 223(h)(1) sez U can't annoy, abuse, threaten, or harass anyone on the Net & elude punishment for same.