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Steps to make a bomb in a fantasy world.

  • Take a piece of wood.
  • Wood is porous. Saturate these pores with oxygen.
  • Saturate the wood itself with Pyro Mana(Mana that provides heat when released).
  • Saturation is to be done in such a manner that Pyro Mana in the innermost parts starts a chain of Mana activation.
  • Then the inner part releases Mana first then the middle parts and then the outer parts.
  • Cover the surface pores with mineral oil(or any other wood sealer) to contain the oxygen within.
  • Your Bomb is ready. To use, activate release of innermost Mana and throw it at the target in a timely manner. (Use of earplugs and UV glasses is recommended)

Now the Questions:-

Google search resulted in inconclusive results. There are porous and non porous woods. But even the non porous woods have pores in them. My question is whether they are porous enough to store oxygen for starting an explosion.

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  • $\begingroup$ We have a strict one question per post policy. $\endgroup$
    – sphennings
    May 16 at 5:23
  • $\begingroup$ @sphennings Ok. $\endgroup$
    – EMS
    May 16 at 5:24
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    $\begingroup$ are you sure that asking if wood is porous is a worldbuilding question and not a google query? $\endgroup$
    – L.Dutch
    May 16 at 5:31
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    $\begingroup$ Moreover why does it matter what wood is in our world? It could be porous in yours. Ebony is a type of wood IRL. Decently hard but in the Elder Scrolls universe it's one of the hardest metals available. They mine ebony - it's found in ores underground. Similarly in the same universe "glass" is a mineable resource. You go there and pry it from the ground with a pickaxe. Then give it to a blacksmith who can craft it into some of the best weapons or armour in the world. Is that how IRL glass works? No. But who cares? $\endgroup$
    – VLAZ
    May 16 at 6:29
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    $\begingroup$ @Pelinore my vague recollection of a discussion with a scientist once was that a sufficient mass of any (carbon-based?) solid can become a self-sustaining explosion, but that for wood the required mass was something like the size of our moon (with a proportionally large booster charge of conventional explosives to get it started). Which is probably why as a military demolitions supervisor I was never taught to consider wood as a viable option for explosive demolitions. $\endgroup$ May 16 at 23:16

4 Answers 4

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Your search was inconclusive, because "wood" is an artificial term for hardened plant matter, and varies wildly between plant species. Some species have wood so porous you can use it as a sieve, some have composition so uniform it appears as glass.

Now the idea to infuse wood with oxygen: it can be done, but not in great amounts. Your best bet is to pick long fiber softwood (like quick growth pine) or spongy hardwood (like aspen) and wait for it to become punky. Punk wood is what happens when fungi reduce most of the matter inside the wood, leaving a matrix of fiber with flammable dust trapped between layers. It can be infused with oxygen to make a bomb, I just do not think this is entirely necessary. Any kind of combustion reaction like that is likely to sustain itself on the oxygen already present in the punkwood naturally, and in any case, the combustion should happen fast enough that oxygen from the outside could be sucked in. The only time I would consider infusing extra oxygen into it is if you are trying to ignite a very thick log.

To explore this idea more, we need to know how powerful is your Pyro Mana. Is it more like a self-igniting gas, or something more like thermite?

You can go two directions with it, I think:

Option 1: Pyro Mana is basically like free floating, very excited hydrogen; it spontaneously combusts and burns pretty much instantly with any oxygen available. This would make for a pretty reliable but weak bomb when infused into a log of wood. Something between a flashbang grenade and a weak molotov coctail.

Option 2: Pyro Mana is much denser, but burns with far greater energy, sort of like Thermite. This would make a far more dangerous bomb (basically an incendiary grenade that burns hot enough to melt steel) but it would actually require extra oxygen and some finicking with the log of wood (maybe drilling a hole in it, where more oxygen and Mana could be stored as a starter.)

Aside from this consider some options:

  • instead of infusing wood with oxygen and Mana, why not make a wooden jar and fill it with Mana? That jar would thus be far more powerful incendiary grenade, or could be used as a incendiary shell when shot from a catapult. If Pyro Mana cannot be just poured into a jar and has to be infused into wood: fill the jar with finely ground sawdust, and infuse that. Sawdust is highly flammable and even explosive. Miz it with charcoal (which comes from wood as well) to make it even more flammable.
  • The problem with the lack of initial oxygenation and starting heat can be solved with kinetic energy. Make a ballista bolt with a punk wood head infused with Pyro Mana. Shoot it at a target. No need to add extra oxygen: the high-energy impact itself will propel Pyro Mana like shrapnel, so it would ignite from friction.
  • you can also use PAPER instead of wood. Paper is essentially reshaped wood pulp: it allows you to create layers of pores exactly the size and and shape you want. Simplest way to do it would be making something akin to corrugated cardboard, rolling it into a tube, filling it with Mana and sealing the ends.
  • Arguably, it could allow you to make cannons. Wooden cannons did exist, they were very inaccurate and could survive only a handful of shots, but wood is so cheap it does not matter much. Drill a bore into a log of VERY hard wood, like cherry. Pack it with a mixture of Pyro Mana infused sawdust and punkwood. Ram in a shot. Ignite the Mana (magically, or just with an ordinary fuse.) The wood cannon would blast out a shot plus a plume of sawdust fire. You can make fire-lances and even crude handcannons the same way. Their accuracy and range would be hilariously bad, but at point blank against enemy infantry/cavalry, they would be devastating.
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  • $\begingroup$ "wait for it to become punky" or reduce it to sawdust and recompact it loosely, maybe with air bubbles and voids? quicker, but more labour intensive. $\endgroup$
    – Pelinore
    May 16 at 10:34
  • $\begingroup$ @Pelinore, yeah. Sawdust, or go even further and make corrugated cardboard paper out of it. $\endgroup$ May 17 at 6:54
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Don't Use Oxygen Gas

The problem with using pure Oxygen is that Oxygen is a gas which means very low density unless you compress it a lot. Wood is not durable enough of a material to contain significant concentrations of Oxygen gas; so, the only way to get a decent self-oxidizing explosive this way is to place the whole thing inside of a high pressure oxygen tank.

But this leads to a second problem: impregnating organic material with compressed oxygen reduces the combustion threshold of the material. So if you were to compress enough oxygen into the wood's pores to be able to fully burn the wood, the whole thing would spontaneously combust at room temperature, no Pyro Mana needed.

Solid or Liquid Oxidizers can easily pack a lot more oxygen into a small space than Oxygen gas. But, since your goal is to permeate wood, I would suggest a liquid oxidizer like Hydrogen Peroxide. If you soak the wood in a bucket containing a high concentration of H2O2, it will dissolve away the lignin, leaving only the cellulose and a few trace elements behind turning the wood into an even more porous sponge like material which will hold onto plenty of your H2O2 as you then proceed to sealing it.

Don't Seal it with Oil

Sealing an oxidizer with oil is also a bad idea because oils all react with oxidizers; so, it won't be able to seal it in anyway. There are a lot of materials that can be used to safely store high concentration oxiders, but most of them are modern synthetic polymers like ABS, PVC, Polycarbonate, and Teflon or high nickel alloys. So, if this is not a modern day setting, you will need to store your soaked log in a ceramic vessel to keep the H2O2 from just breaking down within a few days... but be careful because if the vessel is too air tight, the H2O2 that does break down and release gas might over-pressure your container and cause it to shatter.

Over all, trying to impregnate wood with oxygen is going to be more difficult, dangerous, and unstable than historical gun powder; so, I do not really recommend this idea unless your civilization has managed to bypass discovering more useful explosives on the path to discovering the chemistry that they need to make this idea work.

Just Make Pyro Mana Self-Oxidizing

Since you are already adding a magical element to the explosive, you should lean into it, because you've already thrown known chemistry out the window. If you want to use impregnated wood as a medium for magic explosives, then make the Pyro Mana purely the impregnating substance. Dissolve the Pyro Mana in a solution of water or alcohol, soak the wood in it, and now the wood is an explosive. There is no reason to have to explain this any further.

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Explosives such as gunpowder and TNT are self-oxidizing: their chemical composition includes both oxygen and another reagent which reacts energetically with oxygen. It takes energy to get the oxygen and the other reagent free of the chemicals they're currently part of, but once they are, they react with each other and release more energy than you paid to free them.

Substances such as wood, which have the other reagent (hydrogen) but are missing the oxygen, may burn, but will not explode. Because solids are much more dense than gases, there is just not enough oxygen around to react with the hydrogen, so the combustion chain reaction can only happen as fast as air currents bring oxygen gas to the burning fuel. And the reaction will stop unless there is a volume of air much larger than the volume of fuel available for the reaction.

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  • $\begingroup$ Purpose of the saturating the pores with oxygen(Pure oxygen, no other gases) is to provide the missing oxygen you mentioned. $\endgroup$
    – EMS
    May 16 at 11:32
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Is wood porous? yes.

Many common woods used in construction are porous, there are of course many different woody plants so there is wide variance in porosity.

There are products that rely on this property such as wood stains and pressure treated wood.

Historically wood handled tools such as axes would be placed in water if they were dry and axe head was loose. Water would be absorbed into the handle swell and the head would not longer be loose.

Explosive wood.

As to is wood porous enough to absorb an oxidizer material such as perchlorates it depends, but it would be reasonable that it is possible by some combination.

Or could go the extreme of applying some liquid oxygen to the wood and has good odds of turning it into contact explosive. Since spilled liquid oxygen was found to be able to turn asphalt into contact explosive.

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