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  1. Minecraft: Java Edition
  2. MC-102162

Some light-emitting blocks (magma, lit furnace, lit redstone ore) 'save' block light


    • Icon: Bug Bug
    • Resolution: Fixed
    • Minecraft 18w43a
    • Minecraft 16w20a, Minecraft 16w21b, Minecraft 1.10, Minecraft 1.10.2, Minecraft 16w44a, Minecraft 1.11, Minecraft 1.11.1, Minecraft 1.11.2, Minecraft 17w06a, Minecraft 17w13a, Minecraft 17w13b, Minecraft 17w14a, Minecraft 17w15a, Minecraft 17w16a, Minecraft 17w17b, Minecraft 17w18a, Minecraft 17w18b, Minecraft 1.12 Pre-Release 1, Minecraft 1.12 Pre-Release 2, Minecraft 1.12 Pre-Release 3, Minecraft 1.12 Pre-Release 4, Minecraft 1.12 Pre-Release 5, Minecraft 1.12 Pre-Release 6, Minecraft 1.12 Pre-Release 7, Minecraft 1.12, Minecraft 17w31a, Minecraft 1.12.1 Pre-Release 1, Minecraft 1.12.1, Minecraft 1.12.2 Pre-Release 1, Minecraft 1.12.2 Pre-Release 2, Minecraft 1.12.2, Minecraft 17w43a, Minecraft 17w43b, Minecraft 17w45a, Minecraft 17w46a, Minecraft 17w48a, Minecraft 17w50a, Minecraft 18w01a, Minecraft 18w03b, Minecraft 18w06a, Minecraft 18w08a, Minecraft 18w09a, Minecraft 18w14b, Minecraft 1.13-pre1, Minecraft 1.13-pre3, Minecraft 1.13-pre6, Minecraft 1.13-pre10, Minecraft 1.13, Minecraft 18w30b, Minecraft 18w31a, Minecraft 1.13.1
    • Confirmed


      This issue is about block light. For the related sunlight issue, see MC-3961.

      The bug

      Certain blocks "save" block light, emiting it even after the original source has been removed.

      Affected blocks

      • Lit furnace
      • Lit redstone ore
      • Magma


      1. Build a sealed room without any lights in it with a single layer between it and the sky.
      2. Use /setblock to create one of the effected blocks.
      3. Measure the value of block light using.
      4. Put a glowstone block right next to the effected block.
      5. Break the glowstone.
      6. Observe that the lighting value (as seen in F3) has changed.


      • All of the affected blocks are full cubes that emit less than 14 block light. (Non-full-cube blocks such as brown mushrooms (1 light) are not affected, and the effect isn't observable for bright blocks)
      • The resultant light is 2 less than the light value of the block you placed next to it, which is 13 if glowstone is used. This is because the block receives (and thus emits) the light level - 1, and then another - 1 occurs due to going back to you.
      • This behavior randomly decays
      • This behavior when using magma blocks is fairly popular for builds (as it is nice for decorations). If removed, it may be beneficial to introduce a similar behavior within the block's state and use an upgrade path to store the current light.

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            fry [Mojang] Georgii Gavrichev
            ThatGuyWithAWiiU Mateus Torres
            35 Vote for this issue
            26 Start watching this issue