Obsidian farming

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v53.16 · v0.47.05

This article is about the current version of DF.
Note that some content may still need to be updated.

Obsidian farming is a method of producing obsidian efficiently. When magma contacts water, a tile of unworked obsidian spawns on the meeting point and both fluids disappear from that tile. Obsidian is a moderately-valuable stone and both magma and water are renewable, resulting in a theoretically infinite supply of mid-value stone goods.

Floodgate method[edit]

A typical method of farming is as follows:

A rectangle hall, 2 z-levels high is dug out/constructed
Lower level of the hall is fed magma from a pump (otherwise it will fill very slowly)
Upper level of the hall is covered in water (pump is a good idea too)
Water gets removed (by a pump, opened floodgate etc.)
Resulting obsidian (on the lower level) is designated for ramping or channeling (floor between levels needs to be removed for the farm to be reused)

For more advanced farms, one can have multiple layers of magma and water - each new layer adds another layer of obsidian, so this method is far more efficient (N - number of fluid layers, (N-1) - number of obsidian layers).

Bridge method[edit]

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Another, possibly simpler, design is 3 z-levels high:

Uppermost level contains a water reservoir, the floor is channeled out and covered with a retracting bridge (shown in purple), to drop water when needed, and, optionally, a raising bridge (in white) to control water flow; the combination of retracting and raising bridges will result in a measuring reservoir, which drops no more water than necessary. It may also include a door for maintenance purposes.
Middle level is an access room; floor may be channeled out or ramped out from below, but it should not be there. It should include an access door, and optional drains to remove excess water (shown in cyan); the spare water may be pumped back to the reservoir, dumped in the caverns or an aquifer, or left in a large room to evaporate. Outside the farm must be two levers; one controls the bridges in the water reservoir, one which controls the magma floodgate.
Lower level is the magma reservoir; the floor should be intact. The magma supply should be controlled by a magma-safe floodgate (shown in green). Again, this level may include a magma-safe door for maintenance access.

Requirements:

6 mechanisms (8 if measuring reservoir is used), one of which must be magma-safe.
1 magma-safe floodgate
1 bridge (2 if measuring reservoir is used)
3 z-levels you're willing to dedicate to an obsidian farm, with easy access to water and magma.

Operating instructions:

Open the floodgate and flood the lower level with magma.
Close the floodgate.
Retract bridge and drop the water onto the magma.
Unretract the bridge.
If necessary, wait until any excess water has drained away - if you built a measuring reservoir, there should be no water left on top.
Mine the obsidian using channels/ramps.
Haul the obsidian stones to a stockpile.
Repeat.

As a bonus, the obsidian casting process can also serve as a convenient ~~soap maker~~ garbage disposal.

Automating Obsidian Farming[edit]

Using some ye ol dwarfputing and a crucible spanning multiple z-levels, these techniques can be used to cast a large block of obsidian. Of course, mining the obsidian itself and resetting the machine will require some player input, but this method simplifies the process considerably. Plus it's dorfy as heck!

The machine consists of four systems:

The Crucible: the multilevel rectangular prism where the obsidian will be cast.
The Spout: the chamber that is filled with a precise amount of lava or water to be dumped to generate the next layer of obsidian in the crucible.
The Register: controls the bridges that operate the spout.
The Clocks: sends pulses to the register to cause it to update its state and operate the spout; also has a timer that stops the machine after a certain amount of time.

The Crucible:

Pretty simple, choose an entirely enclosed box and designate the space to be carved into stairs.
The box must be entirely enclosed; Otherwise you will have to build up the walls on the sides to hold in the liquids.
Each layer should be the same length and width.
For example: 16x16x16 (i.e. 16 wide by 16 long, repeated vertically for 16 z-levels). Doesn't need to be a cube though.

The Spout:

On the level directly above the top layer of the crucible, mine out the area directly over the crucible and channel out the floor. (It should be the same length and width as the crucible itself).
Place a retracting bridge over the entire channeled out floor.
Have two inputs, one connected to a lava source (which may have to be pumped up to that level) and one to a water source (same). These inputs should use a retracting bridge (my recommendation) or floodgates to stop the flow of lava and water into the chamber.
It is important that the bridges retract upward towards the inside of the Spout. This way, at most a full layer of lava or water is in the Spout at any one time. Otherwise, extra liquid may cause the machine to break.

The Register:

Three binary memory cells are necessary. For instance, the Newton's Cradle.
The first cell (the floor cell) should be connected to the retracting bridge in the Spout.
The second (the lava cell) should be connected to the raising bridge or floodgates that control the lava input into the Spout.
The third (the water cell) should be connected to the raising bridge or floodgates that control the water input into the Spout.
Thus, by toggling each cell on or off, the Spout can be filled with a liquid and then cause the liquid to drop into the crucible. Now it just needs to be programmed.

The Clocks:

There will be two clocks made by detecting a minecart being pushed by a dwarf over a pressure plate on the way to next track stop.
The first is a sequencer which will cause the following to occur:

Close the floor; Open lava input
Close lava input; Open the floor
Close the floor; Open water input
Close water input; Open the floor
Close floor (Reset)

Create a new hauling route, and assign a minecart to it. Create five stops on a loop of minecart track.
Remove all the conditions and make sure the directions to push the cart is proper.
Add a new condition to push the cart after some number of days. This will require some trial and error to get the timing right because the amount of time for the Spout to fill with lava and water will depend on the size of the inputs and the input pressure and the size of the Spout. Different timings may be appropriate for different segments.
Before the tile each stop is located on, place a pressure plate. The leave a significant amount of space between plate 5 and stop 5. (This space will be used for a stopping mechanism, see below).
The plate before each stop should be connected to the floor, water, and lava cells as necessary. See the table below.

Sequencer to Memory Cells Configuration
Plate/Stop	Floor Cell	Lava Cell	Water Cell	Result
1	Closed	Open	Already Closed	Closes the floor and fills the Spout with Lava
2	Open	Closed	Already Closed	Drops the lava onto next layer of the crucible
3	Closed	Already Closed	Open	Closes the floor and fills the Spout with Water
4	Open	Already Closed	Closed	Drops the water onto lava, creating obsidian
5	Closed	Already Closed	Already Closed	Closes the floor for safety. Also may be wise to close the water and lava cells just in case.

This creates the loop.
To automatically turn off the machine, a second clock can be used to act as a timer and integrated to stop the sequencer after a duration.
Create a straight track with a hauling route and two stops
Set the condition to leave the first spot to be a duration, say a two weeks. This will have to be configured by trial and error. Start small and then see how much of the crucible is filled up. Then slightly increase the duration before starting the machine again.
Delete all conditions from the second stop. The cart will get stuck there after the duration has passed.
On the tile of the second stop, add a pressure plate on top of the rail.
The plate will then be connected to a switch that is located between the sequencer's stop 4 and stop 5 (it should be after pressure plate 5 but before stop 5). When the plate detects a minecart it will trigger the switch to divert the minecart from its loop and into a hole that dumps it in an inaccessible spot on the level below (this will prevent a dwarf from taking it to its next stop (stop five) by hand). On the level below, the minecart can be secured behind a forbidden door. Then, when you want to start the machine again, you can unforbid the door until a dwarf takes the minecart and puts it back on the loop. Be sure to forbid the door again afterwards.

Resetting the Machine:

To reset the machine, first make sure to mine out the obsidian in the crucible by digging stairs. Mining stairs can drop obsidian like normal mining but has the added benefit of being able to easily designate as a huge cube and then forget (since the dwarves won't cause cave-ins or otherwise get stuck).
Then make sure that all doors/bridges into the crucible are closed/forbidden/impassible.
Manually edit the hauling condition for the second stop (or remove and reassign a minecart) to the timer clock so the dwarves put a minecart on the first stop for the timer. This will cause the track junction in the sequencer to toggle (since the pressure plate is no longer depressed) and once again complete the loop
Unforbid the door locking away the sequencer cart. A dwarf will pick it up and then put it on stop five. Once the duration passes, a dwarf will automatically move it to the next stop, stop 1, which will trigger the first step and the loop will continue. Make sure to forbid the door again or the machine won't stop.
Then, after the timer duration is complete, a dwarf will push it onto the pressure plate which will cause the sequencer minecart to fall into the hole and become stuck after completing the current loop. Then, open the gates and harvest the glorious obsidian obelisk!

Tips

Forbidding a minecart "pauses" it on its hauling route. This can be useful for troubleshooting or emergency stops.
When setting up the water and lava inputs, have a second set of bridges or floodgates that can be toggled by hand via a lever. Then, those can be shutoff for troubleshooting or building the system. Most usefully, they allow the system to be constructed and tested without the liquids (a dry run) and then they can be toggled on.
Include a floodgate on the bottom level of the crucible that leads a drain. Thus, if it floods or there is an issue, any lava or water can be safely drained before troubleshooting.
Switches often involve a dwarf kicking a cart rather than pushing it. Thus, after the switch, add a track stop (as opposed to a stop hauling route stop) after the switch but before stop 5 and set the friction to max. This will stop the cart, and a dwarf will then come and push the cart to stop 5. Without the track stop, the cart may keep rolling and trigger the machine prematurely.
Make sure all dwarves are clear of the machine before locking the doors and turning it on. Otherwise, they might get frozen in carbonite. May be useful for dealing with invaders...

Notes[edit]

Make sure that temperature is enabled in the settings; otherwise, the tiles will not cool down after the obsidian is formed, and dwarves will refuse to get close, thinking it molten despite no magma being present.
Keep in mind all usual precautions for handling big amounts of both water and magma.
Unlike water, magma normally flows very slowly and pressure doesn't affect magma (unless pumped). Because of this, it's always preferable to pump magma rather than letting it flow, even when the obsidian farming chamber is on the same z-level as magma, or it might take much longer than you'd expect. Pumped magma however will be pushed up by pressure, up to the z-level of the pump.
When pouring water over magma without dispensing the exact amount, you'll probably end up with excess water on top of the obsidian. Make sure your design includes a way to easily dispose of this water.
For the same reason it's usually better to drop water onto magma and not the other way around - excess water is much more manageable than excess magma.
Remember to turn off any inflow before digging out obsidian, or the moment the obsidian holding it off gets dug out it will resume flowing, likely leading to !!Fun!!.
Note that if you add water to a tile which is as little as 1/7th full of magma, you'll create a full block of obsidian. This is particularly useful when you're operating a repeatable magma piston since one block of obsidian will displace 7/7 units of magma, and you'll only need 1-2 units of magma to make a block of obsidian to get 7 units of magma.

Obsidian farming

Contents

Floodgate method[edit]

Bridge method[edit]

Automating Obsidian Farming[edit]

Notes[edit]

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