Heavy Furnace

Heavy Furnace is a special furnace used for smelting ore into bars. Like other furnaces, it requires ore in the player’s inventory and is activated while Coal is available. Each smelting operation consumes 3 Coal, regardless of the material being processed or the time required.

Heavy Furnace produces a larger batch of bars than a normal Furnace. Each output stack size is equally likely, so ore has a 50% chance of producing 5 bars and a 50% chance of producing 6 bars. Compared with using normal Furnaces, smelting bars with a Heavy Furnace saves, on average, 9% of the ore and 45% of the Coal.

Because the output is randomized between 5 and 6 bars, it is best used when the player wants to process ore in bulk rather than one stack at a time. The fixed Coal cost also makes it straightforward to plan around, since every operation always uses the same amount of fuel.