Furnace

A Furnace is a special block currently only available in the Indev, Infdev, and Alpha versions of Minecraft. Before the furnace appeared, smelting was accomplished by creating a fire and dropping the ores into it. Now the furnace has its own smelting menu where several smelting operations can be done. It consists of one field for the object that will be smelted, one field for the output object and one field for a fuel. The fuel used can be either log, plank, stick, coal, or a bucket of lava (plus chests, workbenches and fences, none of which are very efficient).

Each operation takes 10 seconds.

A pickaxe is required to pick up the furnace. When the furnace has items inside it, do not try to pick it up, because it will destroy the items inside.

The furnace will take time to smelt objects, but it will also work when the smelting menu is closed, as long as there are still objects to smelt and there's enough fuel. If all objects are smelted, the furnace will stop using fuel. When the fuel runs out, the heat in the furnace, indicated by the flame icon, will slowly decrease and when it is gone, the furnace will become inactive. If a smelting process was running, it will be suspended until the furnace is refueled.

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.

As a building material
Furnaces can be useful as building materials, as they take more time to destroy than other blocks. However, since they take eight blocks of cobblestone to create, crafting stone tools may be more useful.

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.


 * 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.


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