Smelting

Smelting is a method of producing refined goods. It has the same idea as crafting: one must put in acceptable ingredients, and a corresponding output will be given. However, smelting utilizes furnaces, blast furnaces, or smokers, which have a unique interface: one "input" field for the object that will be heated, one field for the fuel, and one "output" field for the final smelted product. For example, two saplings (fuel) could be used to smelt one wood (input) into one charcoal (output). Items can also be smelted using a campfire.

Usage and mechanics
To smelt with a furnace, an input material and a fuel must be placed into the top-left and bottom-left slots of it, respectively. The furnace will begin to smelt on its own and will continue to work if the menu is closed and the player leaves. You can tell whether a furnace is working or not by seeing if the furnace is lit or not and if the fire particle effects are appearing or not. When the furnace begins to smelt, it will consume one piece of fuel and the fire gauge will fill up. After a piece of fuel has started burning, you cannot stop it from burning. Once it starts burning, the fire gauge will slowly decrease until it is gone, and then the next piece of fuel will be used. If there is no more fuel left, the furnace will be interrupted and the item will not be smelted. If the fuel is burning and runs out of input, the fire gauge will continue to burn down, wasting the burn time left. Once the fire gauge is out, no more fuel will be used.

As things smelt, an arrow icon represents the smelting progress. Each smelting operation takes 10 seconds, and when it is finished, the item resulting from the smelting will be put into the output field. If the furnace runs out of fuel before the arrow is filled up, then the input will not be smelted and the process will rewind at 2x speed.

If the player leaves a furnace while it is smelting and travels so far that the chunks unload, the smelting process will halt until the player returns. Smelting will also pause if one leaves the dimension the furnace is located in. If the player sleeps in a bed while a furnace is smelting items, the furnace's progress will be 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. Instead, the game sets the time of day to morning.

If a player removes a smelted item from the output field, that player will instantly receive experience for all the items smelted in that furnace, even ones which had already been pulled out by a hopper.

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, blast furnaces can only be used to smelt ores and smokers can only be used to smelt food items. In addition, both blocks smelt items twice as fast as furnaces do. Some items (notably logs) can only be smelted in a basic furnace.

Using a campfire
Items 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. A campfire can hold up to four items at the same time. Once the campfire has finished cooking an item, it will come out of the campfire as an item entity.

Wasting ores
The following ores can be smelted, but in these cases this is unnecessary and wasteful. All of these ores will yield their product freely when mined with an appropriate pickaxe, and give far more experience than when smelted. The ore blocks themselves can only be obtained with the Silk Touch enchantment. Also, these ores may drop multiple items when mined normally, and potentially even more when mined with a Fortune-enchanted pickaxe. Smelting these, however, will always give only a single unit of the product.

Other smeltable items
A note about fractional experience values: For fractional 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 this grants a 10% chance of getting 1 experience point.
 * Or, when smelting 6 sea pickles and removing all 6 lime dye, the value is 0.2 * 6 = 1.2, so this grants 1 point, plus a 20% chance of an additional point.

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 what will 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 top and bottom of the furnace. For larger smelting jobs, a third hopper can feed in fuel and any empty buckets will come out of the bottom hopper. This will automatically feed and empty the furnace so that different materials can be smelted in the same batch with no loss.

Any experience from items smelted is saved even if the furnace is completely emptied by a hopper. If one item is later taken out of the furnace, the player will receive experience for any items that were smelted.

Trivia

 * It takes 10 minutes and 40 seconds to smelt a stack of 64 items in a single furnace, although this time can be reduced by splitting the load between multiple furnaces.
 * Burning logs or wood with wood planks to make charcoal is over 4 times (×4.57) more efficient than using the log or wood itself as fuel. It is just over 1$1/4$ times more efficient than using planks.
 * The most efficient fuel to make charcoal is charcoal itself.
 * Turning coal into blocks of coal is slightly more efficient (x1.11) than using the coal itself as fuel. For 9 coal, you get 80 smelts instead of the usual 72.
 * If you want to use wooden tools as fuel, the most efficient way is to use it until its durability reaches 1, then use it as a fuel afterwards.
 * "Smelting" is a pretty broad term in the context of Minecraft while in the real world, smelting has a more precise definition.