Smelting

Smelting is a method of producing refined goods by heating raw materials in a furnace, blast furnace, or smoker. For example, two saplings could be used as fuel to smelt one wood into one charcoal. The game mechanic works similar to crafting: A player places ingredients in an interface and obtains a corresponding output item from it. But unlike crafting, smelting only uses single-item recipes and gives experience to a player who takes items from the output.

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 will continue 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 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 gold ore.)  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 will not be used until the output slot is again available.
 * The furnace is broken: This will drop the contents of all the slots, any accumulated experience, and the furnace itself.  The currently-burning fuel item will be 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 will continue to run visually but no more input items will be 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 will resume 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.) However, $$ the saved experience count is not reset due to bug.

Furnace variants
Items can similarly be smelted in a blast furnace or smoker:


 * The usage and interface for smelting with both blocks is the same as those of a normal furnace; however, each can use only a subset of the furnace recipes. For the allowed recipes, they smelt items twice as fast as a regular furnace, but also use fuel twice as fast, so the same amount of fuel still smelts the same number of items.
 * A blast furnace can be used only to smelt ores, and the same metal items (tools, weapons, armor) that can be smelted by a furnace. Ores include both metal and gem ores, as well as ancient debris.
 * A smoker can be used only to smelt food items as listed below. The end result is what counts; chorus fruit is not included (because the result is not edible), but kelp is (because dried kelp is, even though raw kelp isn't).
 * Any other smeltable items (notably logs and cobblestone) can only be smelted in a regular furnace.

Using a campfire
Food items (the same items valid for a smoker) can also be smelted using a campfire. To do so, the player must a lit campfire, with any of the food items listed in the Recipes section in their hand. Fuel is not required; the campfire is able to cook items infinitely on its own. Smelting an item takes 30 seconds, three times the amount of time it would take if a furnace were used instead. However, as a campfire can hold up to four items and cook them all at once, it can potentially take 10 seconds less than what it would take for a furnace to cook 4 of said items. Once the campfire has finished cooking an item, it emerges from the campfire as an item entity. No experience points are granted.

Food
All food items can be smelted in a smoker.

Ores
All ores can be smelted in a 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 the items automatically. The ore blocks themselves can be obtained only via the Silk Touch enchantment.

Other materials
These items can only be smelted in a regular furnace.

Tools, weapons, and armor
These items can be smelted in a blast furnace.

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.
 * 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 burn more items than can fit in the furnace—both input and output are limited to a stack of 64, but a block of coal burns 80 items, and lava can burn 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.