Print

Please login or register.
1 Hour 1 Day 1 Week 1 Month Forever
Login with username, password and session length

[Schmaven]

So I filled a 7-Z pit with magma, right up to the top, and am trying to add water to turn it into obsidian, but it's not as smooth a process as I had envisioned.  The obsidian doesn't sink to the bottom of the magma pit, but just sits on top, blocking all the water.  I assume I have to make some sort of obsidian layer on top, then drop it in a similar way as digging down through aquifers.  My mistake may have been filling it entirely 7-Z deep with magma before switching to water.  1 layer at a time now seems like it would be a quicker process, but it's too late for that now.

Do you think it would be faster to drain it off the map edge or keep using water?  Or maybe both options at once? 

[PatrikLundell]

You could channel away everything along the edges, leaving one tile, hook the obsidian layer to a support that's hooked to a lever, remove the last edge tile, withdrawn the dorfs, and then drop the whole layer by pulling a lever, but you'd still have all the other layers, as well as the rim, so draining and restarting from the bottom up is probably faster (and doesn't splash magma along the edges of the pit).

In order for obsidianizing magma to sink it has to be unsupported, otherwise it fuses with the supporting sides, as you've discovered.

[Loci]

You could just dig out the obsidian layers using downstairs and obsidianize the magma from the top down one layer at a time.

[Schmaven]

Designating the whole area led to cave ins and many miners died.  I dug a little irregularly afterwards, so the Z-Depths are not very even.  There is an obsidian valley into the magma, filled with water, and whenever I try to channel the rim of it out, it just makes more obsidian, but only uses up a few units of water and magma.  I've dug the same square dozens of times now.  I tried channeling out the Z-layer above, and then a ring around the middle to drop it, but despite only magma below, it does not drop down.  Now I have an inaccessible floating island of muddy obsidian.  I've started to dig a drain from the pit as obsidiafying several Zs of magma from above is painfully slow, and costs many lives.  The tricky part being that when the crust is obsidian, channeling down exposes the magma beneath, and dwarves seem to prefer channeling out the ground under their fellow dwarves whenever the chance presents itself.  That combined with the size of the magma pit has cost 2 years of excavating with not even 1 Z level fully cleared.  If I had a large population it wouldn't be as big of a deal, but only I'm down to 45 now, and migrants usually don't come to this fort. 

Downstairs is a good idea, I hadn't considered that.  No more cave ins!!!  ...Face-palm moment...

[Schmaven]

So simultaneously draining the magma while digging stairs on top is not a good idea.  The miners couldn't keep up (partly because 10 of them died to cave ins - still an issue when digging stairs apparently), so now there is an obsidian crust over a 2-Z gap above 3-Z of magma, and only 35 dwarves left.  Also I have 2 full Zs of stairs that need to be cleared that seem likely to cause more fatalitites.

Filling the pit 1-Z with magma, adding water to cast it, then repeating for each level, would have been the best approach.  At least hind sight still works

[Sarmatian123]

Turning magma into obsidian usually is the method for folks, when they want to build up into thin air. To shoot birds maybe? You just wait for rain to stop before turning magma pumps on to fill the form. Then you wait for rain to finish the process. No need for bucket brigade or water pumps. I didn't use it so far, because i need "above ground" and no "under ground" to keep dwarves from this rapid process of cave adaptation. However, putting double thick walls out of obsidian could limit amount of bricks used for surface fortress construction and therefore keep fps a wee faster. Now, that I think about it, I could also create in this way a roof, so long it doesn't change "above ground" status of tiles bellow. Hm...

[PatrikLundell]

Wrong! Rain does not cause obsidianization (or else volcanoes would not exist).

Once a tile has been exposed to the sky it remains "above ground", but the "inside" status can be changed.

[Sarmatian123]

Wrong! Rain does not cause obsidianization (or else volcanoes would not exist).

Once a tile has been exposed to the sky it remains "above ground", but the "inside" status can be changed.

I see. I've never done this before, as all my magma workshop were built under roof. To build double wall for few z-levels takes quite many bricks. Less constructed blocks on map translates into less lag, it seems for some reason from my experience. Pouring lava into a form could be a solution to this issue. Thanks for the info about "above ground". I know how to use autostop to drop 2/7 magma from mining cart into one spot. I guess 2/7 water dropped from mining cart will be enough to turn tile into obsidian rock. I guess to obtain obsidian rock floor/roof, I need to construct wall 1 level under from a magma-proof block. Were not there some bug with obsidian floors? Having obsidian fortress from rock solid obsidian sounds very interesting. That would be such a relief from lag. Though it will take quite a longer time to construct too.

[PatrikLundell]

It's good practice to qualify guesses about how things work so readers can understand they're (reasonable) assumptions rather than actual observations.

Any amount of magma (i.e. 1-7/7) + any amount of water (same limits), in either order results in an obsidian tile with no "leftovers" (no floor on top if a constructed stair was above when obsidianized, though). Also note that water dropped from the level above with buckets typically just evaporates rather than obsidianizing the magma, leaving the magma untouched, so the "safe" bucket brigade dropping height is 2 Z levels above. For some reason that doesn't seem to happen with water from other sources (flowing sideways, dropping from above through a pump, etc.), although it might be that the amount of water in those cases masks the evaporation cases.
Also note that there are special (odd) rules for magma flow tiles.

You can build your obsidianization casts from any material (that can be used for building, of course), as constructed walls and floors are magma safe.

Also note that since magma evaporates, you may need to time the dropping of water with the dropping of magma, or at least be prepared to make a new attempt when the previous one failed.

There is an odd feature/bug regarding revealed floors, so channeling/digging away obsidian may not result in an obsidian floor. Building a floor/road (and probably other things) on rock, at least if it's muddy, and then removing it again may result in the natural floor morphing into "soil".

While the number of items in a fortress is a factor for lag (and DF keeps track of every stone/block/etc. used in constructions) contributes to lag, you need to build a lot for that to be a significant factor. Webs in caverns will have an effect after a decade or two, and for some reason (cavern) trees seem to do so as well.

[Jimmy]

Step 1: Only have 1 z-level of magma per casting, multiple z-levels of magma will be a headache and involve large amounts of manual labor.
Step 2: Construct retracting bridges above magma casting level in the same shape as your magma pool. Link to lever.
Step 3: Fill water on retracting bridges.
Step 4: Pull the lever.

Dropping the water onto your magma will cast the entire level, letting you carve it to your desire, then repeat by following the same process.

You can use the method above to cast downwards, but this will mean you're going to have to hollow out all the squares you've cast into obsidian to allow the water to fall through, losing the benefit of non-constructed obsidian walls.

[PatrikLundell]

You don't actually NEED bridges in the shape of the area to be obsidianized, but can use just a single outlet and rely on the water spreading to obsidianize the rest (assuming the area isn't too large so evaporation will stop the process). If you just drop the water from above you'll have to make sure you cut the flow in time so that you have less than 2/7 water in at least some tiles covering the obsidian so you can wait for evaporation to remove the water. Alternatively, you can add water to at least 2/7 and then add a layer of magma using the same principle.

Having said that, a properly shaped bridge set is probably the most efficient setup for an obsidian farm.

[Bumber]

@Jimmy
It's important to make sure you've got an extra z-level between the magma and bridges, or else they can get jammed with obsidian.

@Patrik
I'm pretty sure the water isn't an issue when dropping 7/7 water on an equal number of tiles of 2/7 magma.

[PatrikLundell]

:
@Patrik
I'm pretty sure the water isn't an issue when dropping 7/7 water on an equal number of tiles of 2/7 magma.

It's true there won't be any excess water to deal with for the bridge design, but there will be from the aquifer/river/cavern lake single outlet one.

[Fleeting Frames]

Regarding the OP's setup, a simpler method than layer-by-layer obsidination is granted by the dwarven submarine thread (though haven't tested in latest version):

1) Above your multiz magma area, build 2z boxes that you put water in. i.e. both zs have enough water for magma to obsidianize.

2) Cave in the whole thing. If you're doing this on a volcano pipe, set up floor(s) so that the water box before the cavein won't have support from them, but the obsidian after will, as otherwise the semi-molten rock will eat the whole thing.

3) Enjoy your new (potentially oddly-shaped) pillar of obsidian.

[Schmaven]

Regarding the OP's setup, a simpler method than layer-by-layer obsidination is granted by the dwarven submarine thread (though haven't tested in latest version):

1) Above your multiz magma area, build 2z boxes that you put water in. i.e. both zs have enough water for magma to obsidianize.

2) Cave in the whole thing. If you're doing this on a volcano pipe, set up floor(s) so that the water box before the cavein won't have support from them, but the obsidian after will, as otherwise the semi-molten rock will eat the whole thing.

3) Enjoy your new (potentially oddly-shaped) pillar of obsidian.

I'm not sure that's simpler than the layer-by-layer approach for turning everything into obsidian.  Wouldn't you have to build several iterations of the 2z boxes to drop?