The furnace won't
start until you've got something smeltable, but it immediately consumes the first unit of fuel (the whole lava bucket, in this case) when it starts and that 'charge', so to speak, will continue depleting regardless as to if the furnace actually doing anything. So if you're not on hand to replace the smelting stack, you'll waste some or all of the potential in the lava bucket... including that three iron you spent to make it.
I much prefer coal for furnace operations. 8 stack smelts a full 64 stack of material, and coal's been ridiculously plentiful in most worlds I've seen so far. If you're going for cost efficiency, though, I think planks are the best option (if I remember what the wiki said correctly) -- wood's one of the few geographically (i.e. you don't have to walk/dig a mile to find it) infinite resources. Just keep a good sized tree farm (or several) around. Even a fairly small one spits out 64 stacks of logs pretty regularly, and it only takes 44 pieces of wood to smelt a 64 stack.
So coal to save iron and wood for the lazy. Lava bucket costs iron
I just wish you could have infinite fuel if you had a lava flow running into the furnace.
That would be killer.
Also watching
Like it so far, yeah. Half wish my computer could handle running minecraft (java
) and a capture proggie at the same time so I could join in on the fun.