Furnace

A Furnace is a special block currently only available in the Indev, Infdev, Alpha and Beta versions of Minecraft. Before the furnace appeared, smelting was accomplished by creating a fire and dropping the ores into it. The furnace, when right-clicked, has its own smelting menu where smelting operations can be done. It consists of one field for the object that will be smelted, one field for the fuel and one field for the output object. Logs, planks, sticks, coal and lava buckets (plus chests, workbenches, bookshelves and fences, none of which are very efficient) are all fuels. Each smelting operation takes 10 seconds.

A pickaxe is required to pick up the furnace. Items inside a furnace will be destroyed when the furnace is destroyed.

Smelting will work when the smelting menu is closed, as long as there are still objects to smelt and there is enough fuel. The fire icon diminishes to represent the fuel burn time. When the fire icon diminishes fully, another fuel item is consumed and the heat is refilled. If all objects are smelted, the furnace will stop using additional fuel. If there is no fuel left, the furnace will become inactive. If a smelting process was running, it will be cancelled and must be redone.

Fuel efficiency
* Note that using a Lava Bucket will not only use the lava, but destroy the bucket as well.

** This column is the unit-of-wood-equivalent. Calculation made once the fuel item is converted back to tree logs.

*** The fuel cost of turning a wood block into charcoal (1/8 of a second charcoal item) is already deducted from this amount.

As a building material
Furnaces take more time to destroy than other blocks. However, since they take eight blocks of cobblestone to create, they are an inefficient building material. They are also weaker against TNT than ordinary stone or cobblestone.

Tips and tricks

 * 8 coal will smelt an entire stack of 64 blocks. 43 planks are the next best thing - 43 planks are capable of generating 64.5 smelted blocks. If you want to be really efficient and not lose that half-plank to nothing, put in 44 planks, then take the first two smelted blocks out, and put two extra unsmelted blocks in.


 * Remember that meat (like other food items) won't stack. This means that 1 coal will fuel between 6 and 7 units of meat, depending on how fast you are with re-loading the furnace. Sticks come in handy, as two sticks should be enough to cook an eighth unit of meat without too much fuel left over.


 * The bonus of using planks is that they are a renewable resource. While there is an abundance of coal in many cave systems, the ever expanding distances to find new deposits quickly outweigh the increased burning duration. Trees, however, can be regrown. See Tree farming. Also, after the Beta 1.2 update, wood can be smelted into charcoal with similar properties to coal.


 * A single bucket of lava will allow for smelting of 100 blocks. The largest stack of blocks is 64. Considering that each smelting operation takes 10 seconds, to maximize the efficiency of a lava bucket, place a lava bucket with 64 blocks of unsmelted material (such as sand, cobblestone, etc) and return between 6 minutes and 10 minutes 40 seconds later to remove 36 smelted blocks and insert 36 more unsmelted blocks.


 * Furnaces are very useful for providing light if you have wood byproducts but no logs to make charcoal with or you otherwise have no way to get coal.

Trivia

 * As of the Halloween update, furnaces will face towards the player when placed.


 * As of the January 13th Update, the top of furnaces have a texture similar to cobblestone.

Ofen