When you smelt sponge, if there is a bucket in the fuel slot for the furnace, it will fill it with water. How can you do this with a custom smelting recipe?

Looking at the recipe file for sponge, it doesn't say anything about this

  "type": "smelting",
  "ingredient": {
    "item": "minecraft:wet_sponge"
  "result": "minecraft:sponge",
  "experience": 0.15,
  "cookingtime": 200

Is this hardcoded in the game or is it possible for a custom recipe to do this? If it's not possible, are there any alternatives?


I have no source for this, but I'm pretty sure I heard once that it's hardcoded. That's one of the issues that smelting recipes still have.
It would probably be complicated to program into recipe files, since it is an output in the fuel slot, which depends on the item in both input slots.

  • They could do it as something like if: "bucket" replace:"filled bucket" but I'll find another way of letting people generate lava. Maybe if they're in a GUI and looking at a furnace I can check the slots – pfg Jun 24 '18 at 17:23
  • It was possible a long time already to detect contents of slots and replace them using command blocks, that was also used for custom crafting in 1.12 and before. You could do that. – Fabian Röling Jun 24 '18 at 20:48
  • yeah but with 1.13 I can just have it be a normal furnace by detecting what block they're looking at – pfg Jun 24 '18 at 22:00

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