Furnace

A Furnace is used to heat blocks and turn them into other items. Furnaces are considered one of the fundamental blocks required to advance in Survival mode. Furnaces can naturally occur in NPC villages. Before the furnace appeared, smelting was accomplished by creating a fire and dropping the ores into it. Furnaces are currently available in all versions of Minecraft except for Classic.

Usage
The furnace, when right-clicked, has its own menu where heating 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.

Wood, wooden planks, wooden pressure plates, coal, charcoal, blaze rods and lava buckets (plus chests, crafting tables, bookshelves, sticks, saplings, jukeboxes, note blocks, locked chests, wooden stairs, trapdoors and fences, none of which are very efficient) are all fuels. Each smelting operation takes 10 seconds. Furnaces resemble dispensers, but the two blocks have different uses and similar crafting recipes.

Smelting will continue to work when the smelting menu is closed, as long as there are still objects to heat 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. The furnace will also stop if the output field contains a full stack, or if it contains a different item (e.g., trying to smelt gold ore with iron ingots in the output). 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.

Gold and iron ores can be smelted into ingots. Furnaces can also be used to smelt redstone ore, lapis lazuli ore, coal ore, and diamond ore (obtained with the Silk Touch enchantment) and returns 1 redstone, lapis lazuli, coal, or diamond respectively.

When the items smelted in a furnace are collected, they drop experience orbs equal to the number of items in the stack. This makes furnaces a reliable (if slow) early source of experience. (As of prerelease 12w22a)

Natural occurrence
Furnaces can be found inside NPC villages. These naturally occurring furnaces are found in the blacksmith workshops, which contain two furnaces. They are, however, completely empty.

Fuel efficiency
Sleeping while smelting/cooking items will not speed up the process.

History

 * In an early version of the game, you can have the same effect as a furnace by dropping items on the ground and then burning them with flint and steel. This was the only way to smelt ores.

Since the Halloween Update, furnaces will face towards the player when placed. Before the update, they faced away when placed.

Since the Beta 1.2 January 13th update, the top of furnaces have a texture similar to cobblestone. They used to have a texture exactly the same as stone.

Since Beta 1.8, you can now cook up to 64 pieces of food at a time. Since meats can stack, it's possible to cook them like any other item. Before 1.8, the player could only cook 1 piece of food at a time (e.g. a single porkchop).

Before the Beta 1.9 pre-releases, furnaces took longer to destroy.

After the official release of 1.2.5, players could use Shift+click to put items into furnaces more easily.

As of 1.3.1, when using lava for fuel you get the bucket back.

In 12w39a, furnaces only lit up blocks in front of them, rather than all around them (images showing difference) This was reverted in 12w40a until the new lighting system could be optimized.

As a building material
Since the Beta 1.9 Pre-releases, furnaces no longer take as long to destroy. Since they take eight blocks of cobblestone to create, they are an inefficient building material. Placing furnaces adjacent of another furnace is more difficult as well, as right-clicking the existing furnace will pop-up the furnace menu rather than allowing to build the furnace. This is altered as of 12w49a, as a player can now shift-right-click to place on blocks that otherwise would open a GUI, or perform another function. The player always has to build against another non-furnace block. Furnaces are weaker against TNT than ordinary stone or cobblestone.

Tips and tricks

 * 8 Coal or charcoal will smelt an entire stack of 64 items. Wooden Planks are the next best thing, with 43 being able to smelt an entire stack of 64 items.


 * The bonus of using charcoal or other forms of wood is that they are a renewable resource, and capable of being made by 2 pieces of wood (1 ingredient and 1 fuel per coal). While there is an abundance of coal in many cave systems, it is still necessary to search out new deposits. Trees, however, can be regrown (see tree farming).


 * Blaze rods are another renewable source of fuel, as they last 50% longer than coal, although the player has to actively farm them in the nether fortresses, which aren't easy to find to begin with.


 * 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 can provide light if you've run out of torches, and they can make charcoal for use in torches. Through this they can essentially be used as fireplaces (since there is no specific fireplace block currently in the game) by placing lots of long-lasting fuel items in it (lava buckets for an example), and then "lighting" the fireplace by placing a burnable item into it.


 * For a large project, you can use more than one furnace, it is not uncommon to see a wall of furnaces near a large project, not used all the time, but to reduce the amount of time it takes to smelt a large number of items. When working at this scale, the most efficient fuel would be coal (or charcoal).  The most efficient method is to use about 16-32 furnaces and use 4 coal/charcoal for fuel and 32 of the blocks that need to be smelted.  This can convert an entire inventory's worth of resources in the timespan of around 10 minutes.


 * The furnace is featured in the "Hot Topic" achievement and is required for the "Acquire Hardware" and "Delicious Fish" achievements, because you need to smelt iron and cook fish for those achievements.


 * Since all types of logs burn for the same amount of time as wooden planks, converting logs to planks is a quick and easy way to quadruple the burning time (instead of 16 logs burning for 240 seconds, converting them to 64 planks would burn for 960 seconds).

Bugs

 * There is a bug where you can use an infinite amount of fuel in a furnace. First, put any fuel and anything you want to smelt in the furnace. Then, when the fuel is almost out, quit and log in again. The timer for the fuel should have restarted, but you will still have the smelted product from the furnace. This can be used for large-scale projects and infinite smelting. The only problem is you need to constantly log in and out if the fuel does not last long.


 * (360)It is possible to duplicate items by using a furnace. First, put the item you want to be duplicated in the furnace. Next, mine at the furnace with any level pickaxe until almost broken. Right before it breaks, switch to a sword of any level, causing an error for the furnace to drop the item but still stay inteact,with the original item inside. Sometimes, the item/furnace will disapear if the sword is switched to too soon. When doing this, make sure to have only one of the item you are trying to duplicate in both your inventory and your hotbar.

Trivia

 * Furnaces function as multiple devices combined into one block. Furnaces are really Bloomeries and blast furnaces (for smelting ores), an oven (for baking and cooking), a charcoal pit (for the charring of wood) and a kiln (for baking of clay).
 * Despite paper being a burnable resource in the real world, you cannot use it as fuel. This might be the case because it doesn't burn for very long, and it only creates a small flame at a low temperature.
 * Furnaces can be used as an early-game XP farm, but on the one hand cobblestone, food, etc. don't give much XP, on the other, it will take a while to produce the materials for an Enchantment Table. Later, smelting accumulated ores etc. becomes a way to controllably gain experience in fair-sized chunks; a stack of iron gives 45 XP, while a stack of gold gives 64 XP.