Making Fire Burn Forever on Netherrack, Magma, and Soul Sand

The eternal-fire blocks

Fire Spread Tweaks normally extinguishes fire after a short delay, but three blocks are exempt: netherrack, magma, and soul sand. Fire placed directly on top of any of these keeps burning indefinitely, just like vanilla nether fire. This is the intended way to build permanent light sources, forges, and decorative braziers without using torches or lanterns.

Building a permanent fire feature

1. Place the special block where you want the flame — a single netherrack block works, or a full soul sand platform for a themed build.

2. Ignite the top face with flint and steel or a fire charge. The flame should stay lit and never time out.

3. Surround the block with non-flammable material (stone, deepslate, bricks) so nothing nearby can catch, since doFireTick is off but you still don't want accidental ignition from other sources.

4. If the fire does go out, you probably ignited the side of the block or a neighboring block instead of the special block's top face. Re-light directly on the netherrack, magma, or soul sand.

5. For a fireplace look, stack magma blocks under a grate or use soul sand with soul fire for a blue flame.

Because these blocks bypass the burn timer, they're the only reliable way to keep fire alive long-term with this mod installed.