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Scenario: In the medieval ages, Our brave hero, without his trusty shield and sword, is surrounded by enemy mooks from all sides and needs a miracle to escape. Fortunately, he has one such thing, having met a miracle seller in the morning. He is in possession of several small orbs, roughly the size of golf balls (if golf had been invented then) filled with an explosive substance, which he can lop at his enemies, scaring and injuring them.

So, the miracle seller asks that in the middle ages, what could he use to create an explosive (gun powder was not discovered then) ?

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    $\begingroup$ Golf was invented in Netherlands in Middle Ages - reported around 13th century $\endgroup$ – Peter M. Jun 22 '16 at 22:23
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    $\begingroup$ Gunpowder was invented in the 800's CE in China and made it to Europe by 1300. The middle ages are defined as "from the 5th to the 15th century", so there's a century overlap between gunpowder in Europe and the Middle Ages. ("[...] Europeans encounter[ed] gunpowder and firearms [...] at the Battle of Mohi in 1241") Also, since gunpowder is the first known explosive, you're just plain out of luck if you're looking for something that came before it, unless you want to bring magic or divine powers into it. $\endgroup$ – HopelessN00b Jun 22 '16 at 22:58
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    $\begingroup$ Plenty of other things cause explosive chemical reactions as well. No reason sodium, lithium, etc. couldn't have been discovered and used in combination with water, for example. $\endgroup$ – fluffy Jun 23 '16 at 0:46
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    $\begingroup$ If I were engaged in vigorous activities where I am bound to receive some bumps and jolts (e.g. involving shield and sword), I would definitely not want to be carrying in my pockets anything that could explode on impact :-) Gunpowder luckily seems to be fairly stable, and unluckily would require some sort of detonator. $\endgroup$ – fr13d Jun 23 '16 at 9:50
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    $\begingroup$ @fluffy the problem is that explosively reactive things like sodium are never found waiting to explode: across the aeons they've had plenty of opportunities to react with oxygen, water, pretty-much-anything already (in fact sodium metal was only isolated in 1807 by electrolysis, i.e. firmly post-medieval). To get hold of any such explosive it probably needs to be something produced by active chemistry, e.g. a plant producing ether as a scent to lure pollinators $\endgroup$ – Tom Goodfellow Jun 23 '16 at 10:58
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Gunpowder was invented in the 800's CE in China

Your Mystery Salesman has obviously been there. Either that or he had someone in the family or in the business where he worked at, that — through various misadventures — went to China and either got hold of a big sample of gunpowder, or a recipe.

If you go with the latter, that recipe unfortunately got lost in a huge explosion that killed those that were working with it, leaving Mystery Salesman with only the stocks of what was manufactured so far, to peddle for money to help him get over his misfortune of having had his employer / family home blow up.

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  • $\begingroup$ No need for a big explosion, maybe whoever came back with fireworks only came back with the products and wasn't initiated into how to make them. The big question, however, would be: is the compound stable enough to remain explosive after weeks/months of travel (and NOT explode during travel) ? $\endgroup$ – Matthieu M. Jun 24 '16 at 9:07
  • $\begingroup$ @MatthieuM."maybe whoever came back with fireworks only came back with the products ". I did say that. "...and either got hold of a big sample of gunpowder, or a recipe". $\endgroup$ – MichaelK Jun 24 '16 at 9:11
  • $\begingroup$ Yes, but you did not explain whether the compounds is stable enough to survive the travel (I have no idea). Do you think it is? $\endgroup$ – Matthieu M. Jun 24 '16 at 9:12
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    $\begingroup$ @MatthieuM. Would it hurt you to Google a bit? In any case... considering how armies were marching all over continents with the stuff and were able to make it go "boom" when needed, I would say: yes. if packaged with care, it can survive that long. $\endgroup$ – MichaelK Jun 24 '16 at 9:15
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I'd say the miracle worker had the ultra secret almost forgotten formula for greek fire.

It was an incendiary liquid that ignited on impact. Bottle it up and throw it at your enemy and he is guaranteed to be distracted. What it actually was really is lost, a now forgotten, closely guarded Byzantine state secret. It was used to fire ships and would burn even when floating on water.

Reference:
https://en.wikipedia.org/wiki/Greek_fire
https://en.wikipedia.org/wiki/Early_thermal_weapons

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    $\begingroup$ It also apparently makes the blackwater burn green! $\endgroup$ – EveryBitHelps Jun 22 '16 at 20:34
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    $\begingroup$ Greek fire was probably very similar to modern day napalm. There is no indication that it exploded, and neither does it seem that it burned without igniting it. $\endgroup$ – vsz Jun 22 '16 at 21:23
  • $\begingroup$ No explosion indeed. But it did ignite on impact, see en.wikipedia.org/wiki/Early_thermal_weapons $\endgroup$ – Bookeater Jun 23 '16 at 6:00
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    $\begingroup$ [citation needed] $\endgroup$ – OrangeDog Jun 23 '16 at 9:09
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    $\begingroup$ The reference for it igniting on impact is page 302 of "The Routledge Companion to Medieval Warfare" and conflates two ideas unpersuasively: "Greek Fire, generally shot from a siphon ... its effect was to ignite on impact" - we don't generally think of a pumped stream of liquid as "impacting" exactly and clearly there's the opportunity to ignite it at the siphon (like a flamethrower). $\endgroup$ – Tom Goodfellow Jun 23 '16 at 13:46
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If the seller is really willing to live dangerously, the orbs could be filled with any of a number of nitrated hydrocarbons with detonators built in by sloppy process control. Nitric acid is commonly believed to have been discovered in the 8th century by the Arab alchemist Jābir ibn Hayyān, although this may not be true, and about 1300 is a more certain date, in the sense that it's more certain that nitric acid had actually been discovered by then (although if true, the discoverer remains unknown).

With the availability of strong nitric acid, the door is opened to the entire process of nitrating hydrocarbons, presumably by accident. Certainly, for instance, picric acid (trinitrophenol) was originally produced by nitrating animal horn and resin. Almost any organic material can be nitrated to produce a functional explosive, but safety is an entirely different question. The need for complete neutralization was not known for some time, and this could have very bad consequences. Improperly neutralized picric acid, for instance, reacts with metals like copper to form heavy-metal picrates, which are very shock sensitive. In effect, the explosive can produce its own detonators - and very sensitive detonators, at that.

So one can posit some alchemist after the 8th century stumbling across the effects of nitration, but not managing to maintain sufficient quality control to survive for long. His orbs are prone to going off at inopportune moments, but at least one batch was accidentally produced which is only risky, rather than bloody disastrous.

Of course, due to improper QC, the alchemist took his process to the grave with him, but a few of his artifacts linger. Death by detonation was seen by the Church as prima facie evidence of God's wrath, so the local power structure burned down what was left of his laboratory, and all records of his work ruthlessly suppressed. Except for an obscure copy of his work which molders to this day deep in the Vatican Library, written in an alchemical code which no one ever solved.

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    $\begingroup$ I love your last paragraph there, haha! $\endgroup$ – Renan Jun 23 '16 at 1:42
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Define "medieval ages". It encompassed approximately 1000 years in Europe, the last few centuries of which already had gunpowder. The problem with early grenades (and early firearms too) was that they didn't have contact fuses: you had to light them on fire yourself. Starting a fire (unless you had a lit torch with you) took quite some of time. There were some early contact explosives (for example "fulminating gold"), but they were very unstable. Maybe even better for a mysterious "miracle seller", and its instability (and price) also explains why it's that rare and almost unheard of in your story?

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Edit: I made some changes after seeing David's comments. Thanks David!

Have your orbs be made of glass, and filled with swamp gas vegetable oil. Now have a hole in the orb, which is closed hermetically stoppeed with some special piece of cloth that seals it, but which is flamable. I present you the "gaslotov" oilotov.

You could set the cloth aflame by friction, like a match, via some pulling mechanism. Have something with a rough surface, so that you hold the rough part and do a throwing motion. The rough part stays in your hand, the cloth catches fire by friction as the orb leaves your hand. Medieval grenade!

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    $\begingroup$ This seems implausible. You'd need pretty high-pressure gas to have enough fuel for any kind of attack, and making gas pumps requires fairly sophisticated technology. You'd also need the glass to be thin enough to shatter when thrown but thick enough to contain the gas. Also, the concepts of "hermetically sealed" and "stoppered with a cloth" are prety much diametrically opposed. But, look, if you're going to use a Molotov, why not just use a Molotov? It doesn't have to be gasoline: vegetable oil would probably work; alcohol almost certainly. $\endgroup$ – David Richerby Jun 22 '16 at 21:33
  • $\begingroup$ Oh, and how do you propose to set cloth alight by friction? $\endgroup$ – David Richerby Jun 22 '16 at 21:34
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    $\begingroup$ @DavidRicherby like a match. BTW thanks for the first comment, that was really on the spot. $\endgroup$ – Renan Jun 23 '16 at 1:35
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    $\begingroup$ Matches were discovered quite late. Proper matches exist only since the late 19th century. Before the late 17th century even muskets were fired using a piece of slowly burning rope (which you had to set on fire before the battle, as it was not a quick and simple process) before a mechanical device using flint was perfected. Other priming mechanisms did exist (like the wheel-lock, similar in principle to modern cigarette lighters) but they were very complicated, cumbersome, and took great skill to make them even halfway reliable. $\endgroup$ – vsz Jun 23 '16 at 6:10
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People have already mentioned that gunpowder actually existed for quite a while in China before we started using it in warfare here, so I'm not going to go there.

In general, as long as you have anything that will rapidly create a lot of gas from liquids or solids and/or a lot of heat (most explosives do both), you have an explosion.

Given that you don't want gunpowder, I assume you're looking for something rather low tech. Harvesting seems rather low tech to me. Specifically, I'd like to point you to the bombardier beetle: https://en.wikipedia.org/wiki/Bombardier_beetle#Defense_mechanism

It uses hydrogen peroxide with a catalyst to get a really fast heat-producing reaction. This in itself might be enough for an explosion if enclosed. Otherwise, you could add some alcohol to the mix (vaporizes easily with heat and will burn into more gas molecules in combination with oxygen).

I assume that you could harvest both the hydrogen peroxide and the catalyst from the beetle (though with significant effort). It also requires little thought to come up with the idea. The critter itself already shows you it can create explosions. All that's left is to try to harvest it and combine larger quantities (and make sure the hydrogen peroxide stays away from the catalyst). Making it into something you can easily carry around and then throw to explode at will is a challenge for any type of explosive though. Most early explosives were at risk for not exploding when needed and at risk for exploding when not needed. That however is more of an engineering problem than a chemical one (though partly also a chemical one for some of the substances used).

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As others have noted, several flammable substances existed in ancient and medieval times. "Greek fire", naphtha, maltha and others were flammable liquids most commonly depicted as being shot at the enemy through a tube or siphon. However, records of other uses do exist. Pots filled with naphtha formed a primitive incendiary grendade, which could literally set the enemy aflame. As these substances were inextinguishable by water, they were quite dangerous for classical soldiers. Earthenware grenades filled with quicklime and pitch were reportedly used at the battle of Thessalonike in 904. Other devices include fire-lances and primitive rockets. Other references to explosive grenades and similar military devices are scattered, but no hard evidence exists in Medieval Europe, unlike other places. It is entirely possible that these devices existed and references have been lost, however. The recipe for "Greek Fire" was a Byzantine state secret known only to the Emperor and his chemists. Perhaps your mysterious individual was a Byzantine Imperial chemist with such advanced and secretive knowledge.

Reference: http://gladius.revistas.csic.es/index.php/gladius/article/viewFile/171/172 particularly the section "Byzantine Pyrotechnics". Overall this is an excellent document on Byzantine and general Medieval-style militaries.

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You could have some sort of substance that is under high internal stress. The object could then explode when thrown. One example is glass under internal tension, call Prince Rupert's Drops. I have heard that steel balls that have been in a SAG mill (for grinding ore) can develop internal stresses that cause the steel ball to explode/fragment. Supposedly that is quite scary.

one of the maintenance issues with SAG mills is when doing liner changes the balls get imbedded in the liner - when removed and sit for a while, the steel balls can explode!

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  • $\begingroup$ Prince Rupert's drops weren't discovered until the 1600s, which is several hundred years too late. Also, they're not going to create much more than a distraction. If you watch the various YouTube videos on them, you'll see the presenters wearing minimal safety gear when exploding the drops: typically not much more than eye protection. And carrying around unpredictably explodable steel balls sounds like a recipe for suicide. $\endgroup$ – David Richerby Jun 23 '16 at 7:28
  • $\begingroup$ The interesting thing about Prince Rupert's drops though is that (AFAIK) they're well within medieval industrial capacity, people just happen not to have known about them. So it sort of depends what kind of fiction you're writing -- if it's the kind of fiction that only permits things that actually did happen, aka "non-fiction", then you can't use them ;-) But it's at least plausible for some glass-worker to invent them much earlier and just never make them famous for whatever reason. $\endgroup$ – Steve Jessop Jun 23 '16 at 10:27
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Well, flour is pretty explosive...

In that case, it would be small boxes or mini-barrels or something filled with loose flour, and the outside coated in something flammable. To use, they would be lit on fire, and tossed or rolled into place. The explosion would happen once the box broke open, and the flames ignite the flour, and the finely-ground, highly flammable contents caught fire. This might explode the remains of the box (which might end up as proto-shrapnel), and make a fiery little boom.

Alternatively, an unlit box (or barrel, whatever) could be lobbed near or at a flame source, like near a candle or in hearth. This would break on impact, and when the puff of flour-dust reached the flame, it would ignite explosively in a dust explosion - again a lot of boom and pyrotechnics, but probably little in the way of structural damage. This wouldn't require lighting beforehand, might take lighter and untarred boxes (since it wouldn't have to withstand burning) and if carefully used might not clue pursuers in that an external flame is needed.

(edit: I had the idea that a packed box might explode if it burned hot and strongly enough to burn through the box, and that explosion would be much greater and cause more damage since the flour was under pressure - the difference between dust explosions used for special effects and those blowing up buildings. This might not be the case, as Mark points out... or simply tarring and igniting the box might not be enough to burn through the box and get hot enough to set it off. My apologies).

Little sacks of flour would not work well as they aren't packed or pressurized for the first scenario, and probably wouldn't puff dust freely enough for the second. Something of wood, maybe waxed or oiled to help promote burning, and coated in something robustly burnable, like tar. A really savvy customer might include some metal shards or other junk, since it's the shrapnel more than the fire that will cause injuries from little bombs.

The hard part is going to be ignition... there aren't any ways I know of in medieval times to set off fire at a distance. The 'bombs' would have to be ignited along the principles of fire arrows, already lit and burning sturdily enough to survive being thrown.

This might have been discovered by someone experimenting after seeing flour explosions in action (like a bakery fire... I think it was known at the time that flour and fire went boom), or trying for a bigger boom from flaming arrows (and using sawdust or the like as extra fuel). The pieces were in place and readily available, it would only take someone putting the pieces together to make something workable.

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    $\begingroup$ Aerosolized flour is explosive, because of the huge surface area to volume ratio. Solid, well-packed boxes of flour don't even burn very well. $\endgroup$ – Mark Jun 23 '16 at 5:19
  • $\begingroup$ @Mark - you might be right... I thought I remembered reading something about the packed boxes of flour turning explosive if it managed to stay on fire long enough to burn through the boxes, something like crates exploding inside a bakery or warehouse burning around them. It's possible that I remembered wrong, or that coating in tar is insufficient to burn it to that extent. In that case, just the second type of 'bomb' and a dust explosion. $\endgroup$ – Megha Jun 23 '16 at 7:31
  • $\begingroup$ @Megha: yeah, in a fire in a warehouse full of boxes of flour I suppose that at some point heat will throw a lot of flour into their air where it becomes explosive. For this golf ball you need the impact to both disperse and ignite the flour. The former is pretty easy (at least to disperse some of the flour giving a "puff of smoke" appearance). I'm not prepared to experiment with the difficulty of the latter! $\endgroup$ – Steve Jessop Jun 23 '16 at 10:35
  • $\begingroup$ See Dust Explosion on Wikipedia. $\endgroup$ – mouviciel Jun 23 '16 at 13:37

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