Next test: Firing through magma!
I have created a second liquid-wall setup, using another pair of screw pumps. This one contains magma! In theory, the bolts fired by the ballista should catch on fire or something while they pass through the magma, right?
I admit I completely cheated to make the magma, using DFhack to add the magma in. I have reached the magma sea, and have a perfectly working magma force setup over a magma pipe, but the magma in this embark is just silly far down. I decided to skip a week of work by using dfliquids instead of building a hundred-pump pump stack. Meh.
The setup is just the same as the previous one, with a wall of pumps (these ones made from green glass) on each side of the liquid wall, pumping the magma back onto itself to keep it from flowing out.
First, since I already have them set up and ready to go, I'll fire a silver bolt through the magma. It should melt or something, right?
Huh. Nothing unusual result. My siege operator decided to fire a steel arrow through the magma next.
Nothing unusual happened there, not that we'd expect it to. Ok, time to get serious. Forbid all metal arrows, fire some wooden ballista bolts through the magma.
Half a dozen wooden ballista arrows fired through the magma, not a one of them caught on fire. And it's not that the water is putting the fire out, I'm pausing the game and examining each shot before it hits the water wall.
As an additional check, I dug up some graphite and set up a catapult. Let's see if we can get burning graphite boulders flying through the air.
Nothing. A dozen graphite boulders fired through the magma, none of them caught on fire. None of them hit any of the whales, either. That was disappointing.
I'd try and figure out a way to set the ballista bolts or graphite boulders on fire before firing them, but I suspect the siege operator would either refuse to use burning ammunition, or bleed out in the process of trying to fire them. Still something I might test.
Save has been updated, for anyone who wants to do their own experiments.
http://dffd.wimbli.com/file.php?id=5632