51: Magma Siphon

In order to safely have and use magma, you're going to need a reservoir. Magma is very, very dangerous, so this must be done very carefully. I will describe the best way I've found to draw magma from the volcanic chute into a predetermined area already dug.

First, locate a good place for the reservoir. Consider where you'd like to place your workshops, in a very permanent location. Hollow out a section about 8 by 10 or so. You want it big, to be sure you don't make it too small. 15 by 20 would be a largish reservoir, but still not too big.

You'll need a hallway (green) running from the volcano's edge to a vertical drop that is over your reservoir. Then you need a small hall above it (cyan). In the diagram above, this hall runs off to the right, back to the fortress. This hall should be directly above the other, against the tube of magma. As you can see, the end of the cyan hallway is exactly one z-level above the end of the green hallway, both flush against the obsidian wall of the magma tube.

In the bottom hall, hereafter referred to as the conduit, install a magma-safe floodgate (blue), and connect it to a lever someplace easily accessible, elsewhere in the fort. Be sure to use magma-safe mechanisms, or it will negate the entire project, and you may flood your entire fort. Afterward, wall off the access tunnel (Wall A) using magma-safe stone. Your conduit is now complete, but there are a few more things to do before we drill into the volcano.

Next, install a magma-safe door (purple) in the upper hall. This will prevent backflow once we cut off the flow of magma to the reservoir. Use the lever to open the floodgate, so that the conduit is "open", allowing magma to flow into the reservoir (later).


 Ok, checklist time.
-Wall A installed, and no dwarves are in the conduit.
-Door (purple) is magma-safe stone.
-Floodgate (blue) is OPEN.
-Wall B has NOT been installed.
-Reservoir is COMPLETELY SEALED except for the hole to the conduit, and no dwarves were walled inside.

Have all these conditions been met?

Time to tap the volcano! Designate only ONE SQUARE to be "channeled", the one that has been outlined in yellow.

Here's what will happen: the miner will use the cyan hall to get to that square, and will dig TWO squares with one action. The top (yellow outline) square will disappear, and the square beneath it will be turned into a ramp. The magma will flow through the ramp into the conduit, and down into the reservoir. The miner will leave, and now you should install Wall B (making sure to use magma-safe stone) right up against the door.

DO NOT try to uninstall the door! Consider it lost, as there's too much risk in trying to get it out; it is a safety measure against the possibility of a slip-up in our installment of a magma reservoir for furnaces and forges. Wall B and Wall A are for fort protection against enemies that can use magma as transport AND have the ability to destroy doors and floodgates and the like.

Once the reservoir is all 7s, or close enough, switch the floodgate back to the closed position. Eventually the conduit will be clear of magma, and we should tear down Wall A, and place yet another magma-safe wall against the floodgate, for the aforementioned purpose of base defense.
Congratulations! You've (hopefully) successfully safely tapped a volcano for your own use....