Explosions, mundane and magical

The thread about "Hermetic Flight by Explosion" is tangentially related to a wide-ranging discussion about explosions I have often thought of starting.

First of all, do explosions exist in Ars Magica (with its arguably different physics)? Probably. Flour mills very occasionally did explode in the middle ages, though the idea provided in LoME p.135 that any spark in a mill will just trigger an explosion is preposterous - it takes exactly the right conditions for flour to explode rather than simply start a quick flash fire (that can be almost as dangerous as an explosion). In fact, I would strongly suggest errata-ing the (IMHO) poor mechanics of that section.

If explosions do exist, what are explosion "physics" in Ars Magica? This has implications both magical and mundane. We know today that explosions are, in a nutshell, A) very quick "burnups" that create a sudden increase in the local air's temperature - which in turn suddenly increases the air's pressure, making it rapidly expand with concussive force - and/or B) chemical reactions that change something (typically a solid or liquid) into something (typically a gas) with a much higher "natural" volume that it rapidly expands into. But in Ars Magica? If that still holds true, Ignem is certainly an Art that can create explosions "indirectly" (by rapidly heating air), though the case could be made about the need an Auram requisite and/or a lot of Finesse.

Subtly related: how about the sound of explosions? We know today that it's caused by air expanding faster than the sound barrier and thus creating a sonic boom. But in Ars Magica? Is sonic boom even a thing? Maybe the "crack" of a whip (you make the tip of a whip travel faster than sound and thus create a small sonic boom) has a different explanation? Does really fast magical travel create sonic booms?

Understanding explosions in Ars Magica helps understanding lightning too. Note that lightning generates a localized explosion by heating the air it passes through; thunder is the associated sonic boom. But you can create a thunderclap without a shockwave (Jupiter's Resounding Blow) and a lightning paired with a shockwave without a significant thunderclap (Incantation of Lightning is likely to knock down stuff close by, but apparently it is not deafening; then again, it's highly unnatural lightning, so maybe it's ok if it's silent?).

Last but not least ... black powder and mundane explosives! If explosions follow the same physics as in our world, black powder is possible. In the real world, it arrives in Europe, probably brought by the mongols, just a few decades after 1220 - so at a time when many sagas will be active. It seems it might have been used in battle by arab forces as early as 1260, and certainly in 1267 Roger Bacon writes about it (though not about firearms) in his Opus Majus. Surprisingly Lords of Men - that does look at weapons appearing even later - spends not a word about it. Is mundane black powder a thing in Ars Magica? And if so, what are the "mechanics" for its creation? One could imagine using the Natural Philosophy rules for alchemical reagents from A&A, but they are not very well-suited: in practice creating black powder - and quite a lot of it - takes significantly less than a season of work once you have the right formula. Of course, maybe black powder is not mundane in Ars Magica, but a faerie substance (the mongols make good faeries, after all) and producing it is faerie wizardry!

If "mundane" black powder is a thing, how about magically created black powder? It seems it would take pretty low levels of Terram magic to create vast explosive potential; this may unbalance the game and devalue Ignem further. Though perhaps saying black powder is an "unnatural" (i.e. solid and quiescent) form of Ignem would help - not the least because mundane fire using magical fuel is not magically resisted - the same should then hold for explosions! One could also say that it would take excessive finesse to magically create black powder, but in practice it's not that hard a process compared to many others that craft magic can easily pull off. In fact, on a related note, it should not be too hard (once one gets the physics right through e.g. alchemical research) for Ars Magica to create other combustible substances at just the right density for an explosion, contrary to what ToME p.135 says (did I mention how little I like those mechanics?)

So folks, what do you think? Has anyone seen a saga progress into the second half of the 13th century (I would expect quite a few to have done so)? Have you introduced black powder in your sagas to match its appearance in historical Europe?


I will just clarify a point regarding modern explosion. Explosions are the result of a very fast decomposition of a solid or a liquid into gases. The density ratio between solid/liquid and gas is several thousands (forget the details of the chemical equation), so once the decomposition happens, there is a huge amount of gas that is generated into a tiny volume and wants to expand, thus creating a huge pressure wave expanding in all directions: that is what is creating the damage and destruction.
The exploding sound is the result of this huge pressure change, almost a side effect.

So to decompose step by step:

  1. Initial stage: a liquid or a solid
  2. Activation: through sparkle, fire or shock (depends on the explosive substance)
  3. Quasi-instant decomposition: releases of high amount of gases in a tiny volume, exothermal reaction, releasing energy (thus heat)
  4. Expansion of the gases: the shockwave, however the initial heat is very quickly disperse, so unless the explosion is projecting flaming liquids or burning particles, damage from pure fire is limited unless at the explosion point. This pressure wave can damage internal organs (depending on the distance and the explosion intensity, so bypass armor) on top of the flying shrapnel that will also do damage (from the outside, so armor will protect).

Since my knowledge of medieval science is close to nil, I don't know which parameters can apply to medieval explosion's mechanics.

To have large area burnt by an explosion, the explosive must be mixed a combustible fuel, and the combination of both that achieves blast effect (near instant destruction) and fire damage (lasting effect) spread by the explosion.

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That's one mechanism. But "pressurization via heat" is another, and that's the one causing dust (including flour) explosions; thermonuclear explosions; and lightning shockwaves. It also contributes in part to explosions such as those from gunpowder. Heat-based explosions do cause significant heat damage to their surroundings - though yes, the main damage is still generally concussive.

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Flour explosion is due to combustion of flour, triggered by a spark. It follows all the phenomena I described in my previous message.

Lightning explosion is pure heat pressure phenomena due to brisk density change triggered by nearly instant heating, but it is one to two order of magnitude lower that "regular explosion" (density change of air due to temperature is 10 to 100 times - roughly - vs thousands fold for solid/liquid turned into gases), meaning that you need to be pretty close to be affected.

Nuclear explosions are a completely different beast and out of scope for Mythic Europe.

Leaving the rest aside: gunpowder was firstly developed by chinese seeking immortality through alchemy.

I'd say in Ars, gunpowder might not be a natural thing, but a magical product, possibly one requiring a variant of the Mythic Alchemy supernatural virtue to be made, and of course, requiring vis.

At the same time, I don't think there's any particular problem in allowing gunpowder to be through standard Natural Philosopy. In game terms, is it any different from greek fire? TSE says it can only be mass produced through a series of innovations on the alchemical workshops.
No reason for this to be any different for gunpowder (and I don't think it would be, at that time).

For magically created gunpowder we are still in the same waters: is this any different from magically creating greek fire through a ritual?

Howrever, for balance purposes, it's easy enough to justify that gunpowder is a complex material, requiring guideline 5 at minimum (one cubic pace of gunpowder in exchange for 4 pawns of vis? It might be better to ad a few more pawns and create a wand of Ball of Abysmal Flame with unlimited uses).

To create it through Rego Craft you have the standard limitations of Rego Craft for replicating natural philosophy products (or you can do what I do and just ban Rego Craft completely, the processes for the creation of an item cannot be properly replicated or accelerated through magic because we are talking of a series of very complex processes, ot about a prouction line).

So, for gunpowder: make it magical, but if it's not, I don't think there is much of a problem either way. It's just an additional tool for problem solving, not worse than any other mass destruction thing that magi can do.

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Hmm. Really? On this I may be wrong, but I was always convinced that ti was not (mainly) about the gases released, but about the heat released.

The heat generation mechanism is completely different, but the reason the go "boom" is just the same as lightning: you heat the air.

Well, here's the catch. How closely do you want the next Ars Magica century to mimic the "real world" century? Because in the real world, gunpowder (once known) became relatively easy to produce given the ingredients. You did not need a whole season of work to create a handful of charges.

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This is really far from true. Almost no possible/actual explosions I have had to deal with in scientific study or in person fit into that narrow categorization. Yes, those certainly create explosions, but there are many other types. If we're talking about Mythic Europe, no need to go in modern understandings. If we're going into modern understandings, you might want to do a lot more exploration of the topic before theoretically explaining it.

As for black powder, I've seen it theorized that it was known in Europe before 1242. So it wouldn't be unreasonable to allow it through experimental philosophy. But it could just be magical, too. Each troupe should probably decide.

But isn't this the same for everything else? Every piece of technology?

At the beggining you won't have mass production of gunpowder (and it might be better to remember it was fairly lower quality than modern gunpowder). That's a fact. Then, once the potential for warfare becomes more and more obvious, people start to enhance the production process.

Then, we reach the point of the first firearms... around what, 1350 (assuming here you have enough production and enough mechanical knowledge to produce the mechanical components). But those were prone to problems and were troublesome to reload.

What's the actual concern behind mundane explosives (assuming, as I said, in Mythical Europe they are indeed mundane, not magical)? That they will be unbalanced (which I fundamentally disagree with, tbh)? That technology is going ahead and this will have impacts on the magi?

Right. But the problem is that the rules in A&A do not "scale". They are certainly fit for the first few batches. But after that?

Sure sure. But you see, as I wrote, just black powder on its own can create issues. If it counts as dust (I guess it's neither stone nor metal), it takes really, really low level CrTe spells to create large masses of it, with much more damage potential than high-level Ignem spells. Furthermore, if it takes ... a mundane a season to create a cartload of it? Then with Rego craft magic you can easily assemble something, with relatively low Finesse, that can pulverize dragons bypassing their Magic Resistance. Etc.

Well, the first question is indeed: do we assume they are mundane, and soon (within a few decades) mass produced? That changes a lot of dynamics (see above) and probably requires new rules (what's the damage inflicted by an exploding barrel of black powder at a distance of 2 or 3 paces?). Not something bad, but something I'd like to see discussed, because I feel I am on deeply uncharted ground.

If, on the other hand, black powder is supernatural ... well, that probably creates a divergence between "real world history" and "Ars Magica" history. What are the consequences? Again, I am not complaining, I am just encouraging discussion about it. Let me put it as a very simple pair of questions:

1. Have you had a saga reach 1270 - i.e. 50 years after the "official" ArM5 date?
2. If you have, has black powder made its appearance in it?


Most of the explosions that would have happened around the start date of AE are actually closer to a (tiny) nuke than to that produced by modern explosives. We are talking about Fuel-Air Explosions. They are also called "Dust Explosions", "Thermobaric Weapons", and "FAB/Fuel Air Bombs". This is the type of explosion that happens in a grain mill or coal mine.

Why are these like a (tiny) nuke? Because compared to modern conventional explosives, about half of the total energy released rather than a few percent is thermal radiation. When larger ones go off they even look like a small nuke, complete with mushroom cloud. Unlike both nukes and conventional explosives, the ground zero for them can actually be pretty massive. And for those wondering, weapons using this style are the most powerful non-nuclear weapons in the world today.

Our Saga is over 100 years post "official" ArM5 date. Black powder has made an appearance but it is very minor. It can only be created by magic or alchemist process, so in our Saga it is "magic".

Magi are not interested in creating it since it is something that can give mundanes enough power to challenge them and alchemist can not produce it in great enough quantity to make it anything other than the rare oddity. That oddity is more used for fireworks than weapons.


Medieval flour mills would not explode. Simply speaking a flour mill explosion does not occur in the milling mechanism, but in the elevators- massive containers which contain either the wheat to be milled or the flour which has been milled. When the dust of either of these mixes with air inside the building to the right stochiometric ratio and there is a spark in the elevator then there is an explosion. Medieval flour mills did not use enclosed containers like elevators but favored open lidded bins.
And generally speaking no, explosions do not come from heating air. However they do come from heating water under pressure to generate enough steam pressure to forcibly rupture a container. Explosions in coal mines could involve gasses (methane) but it is doubtful these were investigated enough to make the connection. On the other hand medieval alchemists did a lot of work with acids which could produce hydrogen gas and with petroleum, so the idea that an explosion could be triggered in either a gas or a solid (liquids won't burn, regardless of what they are made of) would certainly be known, though perhaps not as common knowledge. The most commonly known example of an explosion would probably be the cooking pot with a weight on the lid exploding when it built up too much pressure.

There are vague rules/ideas presented about moving from A&A experimental philosophy to greater production. Look at Greek fire in the Sundered Eagle, iirc.

If it is mundane, as mentioned earlier, magically creating a large amount of black powder, duration long enough, and exploding it, gets around magic resistance.
Will there be an arms race. Will most magi end up having clothing with fire and explosion resistance?

Creating such a mundane alchemical reagent has a pretty hefty Finesse requirement. Also, if you're creating it with a duration rather than a Momentary Ritual costing vis, it's not actually mundane. I'd have to think through more carefully to be sure about the resulting explosion, though.

Now that I'm at my books, I was mostly correct. The rules are actually not very vague at all for moving to greater production. The only part that is vague is just how much Workshop Innovation and Materials you will need to make a workshop for mass production of a given reagent.

Yep. That's what I mentioned.

But on reading in more detail, as far as I can tell the innovations are only to alllow a bunch of people to work in a single workshop sharing the benefit of having the formula and the workshop bonus (such that even someone relatively unskilled can reach Int + Philosophiae of at least 6 and produce "two or more doses in a season"), so they don't really reach large scale production in the way ezzelino is concerned with.

I don't think this is a problem, however. At some point, the rules cease to be a good representation for the tone and period. That's natural, and ties into the other question, regarding how close do we want Mythic Europe to follow history.

Do you have a source on how much blackpowder could be produced by a single workshop, how many people were necessary and how much time? I'm having trouble finding enough details to properly frame this alledged "mass production after a few decades".

But let's put that aside and examine the magic issue first, because magic can theoretically achieve large production either through Rego craft or Creo rituals. So what? Seriously. I mean, is this any different from creating a ritual to create a massive Ball of Abysmal Flame? Or a wand to propel 100 stones, Vilano style, towards a target? In terms of destructive power, gunpowder is not going to overpower magic.

If the concern is just the lack of historically accurate stats for mundane blackpowder, I don't think it's hard to improvise that. Natural philosophy to create gunpowder in small scale, 1 dose can make either a hand grenade or allow one to shoot 10 pellets (I'm just making numbers up). The grenade causes +15 damage at a group (say, 3m radius).

First firearms were slow to reload and had low precision. Say, Atk -5, Dmg +20, takes 10 rounds to reload (again, making the stats up). And don't forget that firearms were expensive, just as it's ammunition. This is not a wildwest scenario where there's a pistol in the hands of every toddler.

Of course, firearms eventually improve, and ammunition becomes cheaper and less prone to expontaneously explode. Say that every 15 years it takes 1 less round to reload the gun OR it's Atk raises by 1, such that in about 300 years we can shoot every round, and Atk is around 5 (once more, just eyeballing it). We'd also need to scale the rules for the production of gunpowder... But by then, so much else on the system needs to change to make Mythical Europe to follow history close enough, because at the end of the day, Ars is a game that seeks to emulate a very specific timeframe. Magic itself breaks if you go forward a few couple centuries.

So a tangential, but maybe worthwile question to answer first could be: current rules support Mythic Europe closely following the technology and lifestyle of historic Europe up to what year?

But back to the main point, I don't think mundane gunpowder really requires a lot of rule or setting changes in about 100~200 years. And if you are reaching 1600's you'd probably want an Ars Early Modernica ruleset for everything else, not just firearms.

Yes, Innovation for this and Materials to have the right special ingredients. But for production, it can ramp up pretty well. Even with each assistant plus the lead making 2 doses a season, with reasonable Leadership this can be a dozen or so doses per workshop. Now the issue is for the production volume to be of a better size.

Let's say the target level is 15 and you've got someone with a total of 20 so they could make it in three seasons. As a long term investment, it'd be worth buying some Philosophiae tractatus to get that person up to 22 over a few seasons (+1 Philosophiae, +1 more that allows). Now you have the person make a level-20 version over the next 5 years (2 seasons per year) that produces 10x as much as the level-15 version. Now that your workshop can produce what would have been 120 doses of the original in a single season.

That is essentially what was done with Greek fire, as a dose is a 10-use amount of the basic size.

With lower target numbers, this can work a lot better, with each workshop producing on the order of 1200 or 12000 doses a season. Of course, with really high target numbers, you probably won't be able to pull this off at all. The numbers are reasonable for a researcher to pass 20, but passing 25 is way up there.


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I think the reason why you are having trouble is that if you have the proper ingredients (and you know the formula) it's fairly straightforward to churn out large quantities of black powder. The ingredients are saltpeter, charcoal, and sulfur, and basically you have to just pulverize and mix them (in the right proportions) ... and make sure the result stays dry and away from fire. Given the ingredients, a proper place and some basic tools, a person can create many tons of black powder in a season after receiving just basic training. Now, both charcoal and saltpeter can be readily made given ingredients common throughout mythic Europe, again at the tune of several tons per person per season. Sulfur is the only slightly trickier ingredient to procure; in the proper places - basically near volcanos, e.g. Sicily and Iceland - it can be mined (again, tons/person every season). Note that all three ingredients where widely known and produced since antiquity.

Which brings up another crucial point. Making black powder (if it works as it does in the real world) requires really, really low levels of finesse if starting from the ingredients. And getting the ingredients in the proper places requires little finesse too ... I'd say the trickiest part to get right is charcoal, which frankly isn't that hard to make with a little experience.

Let's be clear. There are three "technology" levels here.

The first is black powder. Explosives. These are first mentioned in a book published in Mythic Europe in 1267, which probably means there are several people who know about it at least a decade, maybe two before that. In fact, there are (somewhat unreliable) reports of their use in battle as early as 25 years before that ... little over TWO DECADES after the official 1220 date. Not very far into the future at all.

The second is are primitive "cannons": non-portable (at least, not by a single human) firearms. Again, used in battle in Mythic Europe (if you count the muslim lands) probably as early as 1260, at Ain Jalut. Given that they were competing with established technology such as trebuchets and catapults, they probably worked pretty decently by then, or why use them? If all you care is the noise, just use black powder as an explosive.

Finally, there's portable firearms, starting with muskets and the like. These take much longer to appear, I'll grant you.... but these are really the ones that are not so problematic to model.

So, if you want Ars Magica to follow actual history, black powder comes in play pretty early, a few decades into the "standard" saga beginning in 1220. Not 100-200 years, more like 25-40 years. Basically, black powder as a military technology spreads from a tiny corner of Mythic Europe to become "internationally known" roughly at the same time that the longbow does (well, from another tiny corner).

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For basic dust explosion, I would see two spells:

  • one to create saw dust, coal dust or flour (CrHe) - you only need to create a small quantity of dust in the air, like 5 or 10 percent per volume, in suspension (base 3: create wood in an unnatural shape - dust ?), possibly with an Auram requisit to disperse it in the area of effect ;
  • another one for the initial spark (CrIg) - smallest guideline for an open flame is enough (base 3 as I would consider these dusts very flammable), plus enough modifier to be far away from the explosion
    In open air, the effect depends on the weather condition, with strong wind, the dust will disperse quickly, so limited effect. In open air, without draft, there will be a loud bang and those close to the center of explosion can suffer some damage.
    In a closed space, like a room, a cave, a church, the damage will be significantly worse because no wind will disperse the dust and the explosion will be confined, so a lot more damage for everybody/everything inside.
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