Smelting

Smelting is a method of obtaining refined goods from raw materials by heating in a furnace, blast furnace, or smoker. For example, raw iron can be smelted to produce iron ingots using coal as fuel. Like crafting, smelting uses recipes to determine what item is produced, but its recipes are simpler. Smelting also yields experience.

Usage and mechanics
The furnace, blast furnace, and smoker share a similar interface: At the upper left is a slot for smeltable item input, below that is a slot for fuel input, and on the right is a slot where output items accumulate and can be removed by the player. Flames above the fuel slot act as a gauge showing the gradual consumption of the current fuel item, and an arrow in the middle gradually fills to show the progress of smelting the current input item.

To smelt, an input item and fuel must be placed into the input and fuel slots, respectively. The furnace then begins to smelt and continues even after the player closes the interface. (The player can still tell when a furnace is working by its block texture showing flames and fire particle effects appearing.)

The furnace burns one fuel item at a time, with the fuel gauge indicating how much of that item's burn time remains. As each fuel item is fully consumed, another one is taken from the fuel slot and the gauge starts over.

Smeltable input items are also processed one at a time, but are not removed from the input slot while smelting is in progress. The arrow indicates how much of the smelting process has completed. When the arrow is full, the input item is removed from the input stack and an output item is added to the output stack. Smelting of the next input item then begins immediately.

Smelting stops under any of four conditions:


 * When the furnace runs out of smeltable items: That is, the input slot becomes empty.
 * The furnace runs out of fuel: The fuel input slot is empty and the current fuel item is fully consumed (that is, the fuel gauge becomes empty).
 * The output slot becomes full: Either the slot has a full stack of the output, or the output contains the wrong output item for the current input item.  (For example, if the output contains iron ingots but the input contains raw gold.)  In this case, smelting (but not fuel consumption) is paused until the output slot becomes available (usually because items were removed by either a player or a hopper).  If a fuel item burns out in this condition, a new one is not used until the output slot is again available.
 * The furnace is broken: The contents of all the slots, any accumulated experience, and the furnace itself are dropped. The currently-burning fuel item is lost, since it is removed from the fuel slot before burning begins. The furnace item may not be dropped if it was destroyed by an explosion.

If smelting stops while a fuel item is still burning (a normal occurrence), the furnace continues to run visually but no more input items are processed. If the fuel is exhausted (and the fuel gauge is empty) when an item is partly smelted, the smelting progress is undone at double speed and the item remains in the input stack.

Smelting is suspended if players move far enough away from the furnace (including going to another dimension) that simulation stops in the chunk the furnace is in. It resumes when a player returns.

If the player sleeps in a bed while a furnace is smelting items, the furnace's progress remains the same as if the bed had not been used and no additional time had passed. This is because when a player sleeps in a bed, no time actually passes; the game simply sets the time of day to morning.

The furnace keeps track of experience for each item as smelting is completed for it, accumulating it in a hidden counter. It remembers the total earned experience even if a hopper is used to remove the items from the output slot. This earned experience is awarded to the next player who uses the interface to remove items manually, after which the counter is reset. (If the player takes some of the output but leaves some in the slot, the experience corresponding to those items is retained by the furnace and not awarded to the player.)

Recipes
All smelting recipes can be used in the furnace, but only subsets are available in the blast furnace and smoker.

Foods
All food recipes can be used in a furnace or smoker. Food can alternatively be cooked on a campfire, which doesn't require any fuel and is faster (when cooking 4 at a time) than a furnace, but this doesn't award any experience and is slower than a smoker.

Ores
All ore recipes can be used in a furnace or blast furnace.

The following additional ores can be smelted, but it's more efficient to mine them with an appropriate pickaxe. Mining them saves fuel and in most cases yields more product and experience, especially if the pickaxe has a Fortune enchantment. Smelting them, though, allows obtaining them from an automatic device. The ore blocks themselves can be obtained only via the Silk Touch enchantment.

Furnace-only
These recipes are exclusive to the furnace.

Gear
These recipes can be used in a furnace or blast furnace to recycle unneeded gear (tools, weapons, and armor).

For fractional experience values, first multiply this value by the number of smelted items removed from the furnace, then award the player the whole-number part, and if there is a fractional part remaining, this represents the chance of an additional experience point.


 * For example, when smelting 1 coal ore and removing the coal, the value is 0.1, so every ten coal you remove grants you one experience point on average.
 * When smelting 5 sea pickles and removing all 5 lime dye, the value is 0.2 × 5 = 1, so this grants only 1 point.
 * The fractional experience stays within the furnace when the final total is not an integer, so the leftover experience is attributed to the next round of smelting.

Fuel
There are multiple fuels that can be used to smelt items. The type of fuel that should be used depends on the number of items in question.

For larger jobs, a single lava bucket or a block of coal can smelt more items than can fit in the furnace—both input and output are limited to a stack of 64, but a block of coal smelts 80 items, and lava can smelt 100 items.

Hopper automation
The smelting process can be automated with hoppers on the top and bottom of the furnace. For larger smelting jobs, a third hopper on the side of the furnace can feed in fuel and, in case of lava being used as fuel, any empty buckets come out of the bottom hopper. This automatically feeds and empties the furnace so that different materials can be smelted in the same batch with no loss.

Whenever a hopper or minecart with hopper removes items from a furnace, any experience earned from cooking or smelting the removed items is saved in the furnace and awarded to the next player who manually removes an item from the furnace's output slot. This saved experience is in addition to that earned for the manually removed item(s).

Trivia

 * A wooden tool burns the same regardless of its remaining durability. A used-up tool is just as effective as fuel as a new tool.
 * "Smelting" is a broad term in the context of Minecraft while in the real world, smelting has a more precise definition.