Blowing up a building with gunpowder and the aftermath

What is the nature of the building? One story or two? Stone, wood, masonry, wad and dauble? What is the nature of the floor? Did they place it in a sub 'basement' or undercroft? Did they tunnel under through soil? Did they 'mine' it - like you would a wall?

Give us something to work with.

First, given your time period, you're talking about black powder, not modern gun powder. Just to be clear. That's what was used in the gunpowder plot, but the gunpowder we think of now is a completely different thing.

There are lots of ways your guys could mess it up... not using enough, not packing it correctly, not placing it correctly given the layout and architecture of the building, etc. Black powder is classified as a "low explosive" as opposed to our modern "high explosives". What that means is that is a very slow-burning explosive. (Only with comparison to high explosives.)

As with any slower burning explosive, it requires overpressure to do its job--it had to be packed in such a way that the burning produces pressure in a container, and then creates a destructive overpressure in whatever you're trying to blow up. Like a building. For example, if you were to put a pile of black powder into an open container, like a bucket, and put that in a field, it would be largely not destructive. It would burn--really, really, really fast--and it would send a nice mushroom into the air, but it wouldn't even destroy the bucket it was in, most likely. But it you latched a top onto that bucket, you'd get a much more impressive explosion. Think of the concept of holding a fire-cracker in your open hand, and then doing the same thing with a closed fist. The first action will cause little damage. The second... you'll lose fingers.

As for where you'd have to place the explosives... somewhere that's going to cause that destructive overpressure. In a basement would be enough, providing that you used enough. Beware of windows and open doors, though, since that will release some of that precious pressure.

The survivors' hearing would likely be effected, yes, depending on where in the building they were. The greatest damage is going to come from debris of the building itself. So if anyone is in the basement with the explosives, they're going to be torn to shreds. Anyone directly above the explosion is going to likely be torn to shreds and badly burned. But as I said, the majority of the damage is going to come from pieces of building flying at high speed through the air, and from having a building collapse on them.

Black powder explosions create a great deal of very, very thick, sulfurous white smoke. The survivors would be cloaked in it. They wouldn't be able to see shit. They wouldn't be able to breathe. And the gas itself can be deadly.

Survivors may well be found in the street, in the walls... it would be ugly. It's hard to say without knowing the layout of your building, the size, the number of floors, and the amount of explosives you plan to use, but people will be thrown through windows, out doors--just remember this. Explosions at ground level always flow up and out. They always attempt to throw things up and out. So if there's little or no resistance, that's where things are going.

Here are some links about properties and such.

http://www.pyroguide.com/index.php?title=Black_powder

http://cameochemicals.noaa.gov/chemical/14053

http://www.pyronfo.com/low-order-explosives/the-chemical-and-ballistic-properties-of-black-powder/

Minor addition to kct webber's post, if the black powder gets wet enough, it won't work. Probably depends on how your guys plan to set it off. If, for instance, they use a fuse and that fuse ends up in a water-soaked patch of powder, no go. If it ends up in a damp patch of powder, it may go (depending on how much damp powder is directly around the fuse). If it's in dry powder, it certainly will go. If it's in a bag of compromised powder – some is wet and some isn't – the explosive yield will also be compromised.

But this also depends on the ignition source. The aforementioned fuse might be a trail of powder (which burns very, very quickly: Foop! all gone), or it might be as simple as a piece of yarn that's been soaked in powder paste and allowed to dry, or it might be a more sophisticated fuse that's been water-proofed and timed (but I don't think safety fuses were invented until the 1800's, could be wrong -- safety fuses being ones that burned at known rates per length of fuse).

As to mucking things up, if they're placing their explosives underground, I imagine the possibility of contamination from the environment, either drippy water or simple humidity, this likely depending on how the powder charge is prepared and how it's packaged. Simple home-made powder, for instance, unglazed, seems to easily soak up humidity. If it's left unused in a sufficiently humid environment, I can imagine it not working at all, or at least not as well.

As to blasting the structure described to smithereeniums, the similar types of construction I've observed (well, multi-story ones) appear to have stone walls with wooden inner floors and stairs. I can imagine blasting the crap out of the wooden parts and setting them afire, but I have no idea how one might take down a drill hall, or any other structure for that matter, beyond the ol' "attack support structures" approach.

Black powder can be set off easier than modern powder. A nice static electric spark could do it, a spark off of a piece of metal definately would.

A lot of this is going to depend upon the volume of your black powder and the size and construction of the walls. It also depends upon where in relation to the walls the explosive is located.

Now if you're going after soft targets (people), you want the explosive set in the middle of the room for maximum effect. I'm not sure in ancient times people understood this to well, however. Usually explosives were set to provide physical destruction.

Assuming that they use passages under the drill hall, and assuming they can measure correctly, let's look at how the blast force would expand. Blast forces always expand in the easiest fashion. If a bomb is set off in mid-air, the blast would expand in a 360 degree fashion. A bomb set off on the ground will expand out and up, but in a very limited fashion into the ground. A crater that ends up ten feet deep might have vertical and horizontal destruction going out a hundred feet or more.

Now a blast set off in a passageway underneath another room is going to expand in a particular fashion. First off, the blast is going to go up and down the passageway for quite the distance. Depending upon construction, you could get the blast force traveling several hundred feet and popping out any openings. The walls of the passageway, however, would receive a lot less damage.

Blast force against the floor again would have minimal damage. However, blast force against the ceiling could be fairly substantial. Presuming the floor is not very thick, it would be the weak point allowing the blast to travel that way. If the floor is thick enough, it would work to contain the blast. Depending upon the amounts of explosive, you'll notice in tunnel blasts to undermine a wall that the blast actually doesn't cause any destruction to the wall above it. The blast creates a cavity underground. The weight of the wall then causes the ground to collapse filling in the void, collapsing the wall.

Assuming your blast is set off underneath one of the walls, which would be your plan to destroy the building, you'd see a lot of destruction under the wall where the explosives were piled, but the wall on the opposite side of the room might have no damage at all.

If the blast is set off in the middle of the room (depending a lot on the size of the room and the amount of the explosives), especially with stone wall, you'd probably see the walls acting to contain the blast, destroying the softer material in the room (i.e., people) and depending upon its construction, the ceiling.

If the ceiling of the passageway isn't too thick and made of light materials, my approach to maximum killing power with minimum effort would be to place a barrel of flour with some black powder in the bottom on top of my explosives, separated by a steel plate. Blast goes off, sending barrel through the floor and then the barrel explodes. The flour then expands laterally catching on fire. It would probably kill everyone in the room without destroying the building.

Best of luck,

Jim Clark-Dawe

I'm not sure if this http://www.aboutscotland.co.uk/mqs/kirko.html will be of any use - it is about the murder of Mary Queen of Scots husband, Henry Darnley, in 1576. The house was blown up.

There would also be noise and vibrations from the blast. I have experienced modern explosions in London and although the force of a modern explosion would, I think, be far greater than one from the past, some effects would be the same. Noise, not just of the explosion but of debris falling to the ground. Dust spreading outwards from the place of the explosion. And the vibrations - which are very scary. Domestic animals also react in different ways - my cat ran up and down the hall like he was possessed.