The Barrel is a device that can hold both items and fluids. The central slot is used to hold items. Fluids are shown in the tank on the left side, and can be added to the barrel by placing a filled bucket or jug in the top left slot. They can be removed by placing an empty fluid container in the same slot. Using Right Click on the block with a bucket also works.
The barrel interface.
Barrels can be Sealed. Sealing allows the barrel to be broken while keeping its contents stored. It also allows for the execution of some recipes. In the interface, sealing can be toggled with the grey button on the right side. Using Right Click on the barrel with an empty hand while holding Shift also toggles the seal.
Barrels are an important device used for mixing various fluids and items together. To use a Barrel recipe, the barrel must be filled with the correct ratio of fluid and items required. Depending on the recipe, it may need to be Sealed for a period of time to allow the contents to transform.
If the contents of a barrel does not match the ratio required for the recipe, any excess fluid or items will be lost. If the recipe is one which converts instantly, however, you will always need at least enough items to fully convert the fluid, according to the recipe.
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A couple barrel recipes operate by mixing two fluids at a certain ratio. This is done by taking a filled bucket of one of the ingredients, and putting it in the fluid addition slot of a barrel that has the required amount of the other fluid. This is done for making Milk Vinegar, where Vinegar is added to Milk at a 9:1 ratio. Vinegar is also added in the same ratio to Salt Water to make Brine.
Barrels have the ability to cool hot items. Put a hot item in a barrel of Water, Olive Oil, or Salt Water, and it will quickly bring its temperature down.
Barrels have the ability to Dye and Bleach items. Most color-able things, like carpet, candles, and Alabaster can be dyed by sealing them in a barrel of dye or bleached by sealing them in a barrel of lye. See the dye chapter for more information.
Barrels can preserve items in Vinegar. Vinegar is made by sealing Fruit in a barrel of Alcohol. For information on how that process works, see the relevant page.
Barrels placed against the side of a block work the same as vertical barrels, but have restrictions on placement. For example, they must have a Barrel Rack added to them with Right Click in order to have another sideways barrel above them.
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Sideways barrels show their sealed state using the Tap. If the tap is sideways, it is sealed.
Unsealed sideways barrels automatically drain their fluid into open barrels (and other fluid containers) placed below the tap. The block the tap extends into must be a free air block in order for fluid to be able to drain.
A barrel dripping.