Merged Furnaces
Fuse several furnaces into one and turn it into a smelting beast.

Overview
A Fabric mod for Minecraft 26.1.2 that adds a single block, the Merged Furnace, which evolves through 10 levels. Every level unlocks more slots, more speed, and ultimately better fuel efficiency.
Parallel smeltingUp to 5 items cook at the same time, each with its own independent progress arrow. |
Stacked fuelUp to 5 chained fuel slots that burn one after another. Load a stack in each and forget about refueling for hours. |
Level preservedBreak it and place it again - keeps its exact level. No upgrade progress is ever lost. |
Visual identityEach level shifts the stripe color on the block and the item following a "heating up" progression. |
Crafting
The base Merged Furnace is crafted with 4 vanilla furnaces in a 2×2 pattern on the crafting table. It starts at level 1.

How to level up
With the Merged Furnace placed in the world, hold a vanilla furnace, blast furnace or smoker in your hand and right-click the block. Each upgrade:
- Consumes the furnace from your hand (in survival).
- Plays the anvil sound as upgrade feedback.
- Bumps the level by 1 (up to 10).
- Changes the stripe color of the block instantly.
- Sends a chat message confirming the new level.
Level progression
Upgrades come in two phases. Levels 1-5 multiply speed and add fuel slots. Levels 6-9 add input + output pairs for parallel cooking. Level 10 caps it with a final speed + fuel efficiency bonus.
| Level | Color | Input | Fuel | Output | Speed | Efficiency |
|---|---|---|---|---|---|---|
| 1 | Blue | 1 | 1 | 1 | 1× | 1× |
| 2 | Cyan | 1 | 2 | 1 | 2× | 1× |
| 3 | Green | 1 | 3 | 1 | 3× | 1× |
| 4 | Orange | 1 | 4 | 1 | 4× | 1× |
| 5 | Red | 1 | 5 | 1 | 5× | 1× |
| 6 | White hot | 2 | 5 | 2 | 5× | 1× |
| 7 | Light cyan | 3 | 5 | 3 | 5× | 1× |
| 8 | Magenta | 4 | 5 | 4 | 5× | 1× |
| 9 | Violet | 5 | 5 | 5 | 5× | 1× |
| 10 | Gold | 5 | 5 | 5 | 6× | +25% |

The interface
The GUI is laid out vertically like a real chimney: fuel burns at the bottom, the item cooks in the middle, and the result rises to the top slot. Slots locked by the current level show a red padlock. Each input has its own progress arrow that fills from bottom to top.
- Top row: 5 result slots (output).
- Vertical arrows: per-slot cook progress.
- Middle row: 5 input slots (items being cooked).
- Bottom row: 5 fuel slots. The active slot shows an animated flame on top.
- Top-right corner: "Lv. X / 10" indicator.

Under the hood
Parallel cookingFrom level 6 onwards, every input slot processes its smelting recipe independently. Each slot has its own timer, so you can run 5 different recipes at once (iron + gold + food + glass + sand, for example). Fuel drains proportionally to the number of active items: if 3 items are cooking, burn time decreases by 3 units per tick. |
Level 10 efficiency bonusLevel 10 introduces two subtle but stacking benefits:
|

Level preservation on break
The block is mined with any pickaxe (registered as a pickaxe tool block) at the same speed as a vanilla furnace. On break:
- Drops the full inventory contents (inputs, fuels and outputs).
- Drops a Merged Furnace item with its level saved. The item icon already shows the matching stripe color.
- When placed back, the block immediately appears at its original level - no level 1 flash - because the component is read at placement time.


Technical details
Block & BlockEntityBlock state with |
Custom data component
|
block_entity_dataSame vanilla mechanism shulker boxes use: the dropped item carries a |
Procedural GUIThe entire panel is drawn with primitives ( |
Installation
- Make sure you have Fabric Loader 0.19.0 or newer for Minecraft 26.1.2.
- Install Fabric API 0.149.1+26.1.2 (or a newer compatible release).
- Drop
merged_furnaces-1.0.0.jarinto themods/folder on both the client and the server. - Restart and craft a Merged Furnace with the 2×2 recipe.
The mod is client + server: both sides need the JAR. The server handles block logic and smelting; the client renders the GUI, textures and the item model.

