Hot solution of sodium carbonate will turn the emulsion to mush. I re-use glass plates, and have never had problems with ghosted images, but I do use a subbing layer, so there is bit of a barrier between the glass and the silver. YMMV.
That's great! Glad to know our historical problems are a thing of the past. I've got a hunch LP Clerc found it nearly impossible to re-use... used, commercially-prepared plates that were easy to obtain in those days.