I am having problems building a working magma forge in my fortress (using the most current version of DF). I have built magma forges in prior versions and am aware that I need to place the "darker green" x in the magma forge template over the hole leading to magma in the Z level below the forge. When I build a forge in my current fortress it apparently builds ok, but when I try to set jobs for the completed forge it says it needs magma under the forge. I have excavated a large open area (approx. 50x40 tiles) one Z level lower in my fortress that is still filling with magma (currently filled to 2-3 depth) from a connected magma pipe. Do I need to wait until the magma fills to a higher level than 2-3, or are there other requirements I am missing to get the forge to work?

  • Wouldn't it be fairly easy to wait until the magma fills up entirely to rule that possibility out? – Frank Apr 28 '16 at 22:54
  • @frank: I overbuilt the area for holding magma to avoid having to risk a 2nd dwarf later (running from a 2nd magma breach in a new location). The oversized magma cavern will probably fill to 7/7 in about two game years at the current rate, and I am anxious to start smelting quickly without using fuel, thus why I built the magma furnace. The slow fill rate is due to a diagonal magma breach; since a direct breach results in a faster magma fill rate but also a fried mining dwarf. – Mark Ripley Apr 29 '16 at 0:55

As indicated in the second paragraph of the introduction to the Magma Forge on the DF Wiki, you need to wait until one of the eight non-center tiles of the forge fill to a depth of at least 4/7.


To build a magma forge, you must have magma-safe materials (non-magma-safe materials will not be shown on the material list), an anvil, and a build site where at least one tile directly beneath one of its eight non-center tiles contains magma at a depth of 4/7 or greater.

Assuming your influx of magma is sufficient to overcome the evaporation process, you ought to be able to wait for a while and the forge will become active.

  • More specifically, whichever tile you have the hole in must be at a depth of at least 4/7. If there is floor between the workshop and the magma, that tile's magma depth is ignored. – Nick May 1 '16 at 17:55

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