Hi I have been casting with a charcoal fueled furnace but the mess it makes is starting to make me want to switch to electric heating. I plan to build a new furnace with kanthal elements and was wondering if I could use a variac to control the temperature. I don't think I have ever seen anyone use a variac to control a furnace. Would it provide enough adjustability? Would it be safe for the variac to be used with the resistive load? I picked up a big 30 amp variac cheap and have not come up with a use for it but I don't want to damage it.