If anyone wants an education in why "slowly burning the explosive" isn't as mad an approach to disarming a bomb as it sounds, please do see the incredibly well informed responses I was rewarded with when I raised a quizzical eye to the technique in my post below.
Unfortunately the best replies were usurped by a telling off from someone who comically misread my tenor, and now the whole thread has been moved from top straight to bottom, presumably as the victim of some anti-controversy algorithm. I know it's not the done thing to comment on such matters, but there's some really great posts in there that people put a lot of effort into, and now they're buried, which, dang, is a shame.
I was also surprised the first time I heard you can safely burn explosives: I was reading some comments on the Vietnam war from veterans talking about how they used to heat their meals by burning pieces of C4.
I mean, the fumes are super not good since there will be a significant amount of N20, but most explosives are very hard to set off. Sure, it's relatively easy to create chemicals that explode, but the real trick is finding ones that don't explode from the slightest bump. For example, Alfred Nobel didn't invent nitroglycerin, he invented a safe(er) way to store and transport it. TNT is actually relatively difficult to set off, even something like shooting it with a rifle won't necessarily set it off. That being said, explosives definitely can sensitize with age, which is why unexploded ordinance is so hazardous.
For reference, my father was an explosives engineer and was the point of contact for local law enforcement when they found old explosives. (this was the 90s,so they didn't have funding for a bomb disposal team and this was an area that had mining history). There were multiple buildings where he advised the safest way to deal with the old explosives (mostly dynamite, but some TNT) was to set an explosive charge near and set them off since handling them would have been too high risk. New dynamite is safe enough you could toss it onto a campfire and it won't do anything more dramatic than burn rapidly (EDIT: not a guarantee, it is potentially possible that a fire could set dynamite off so I wouldn't recommend this, but anyone who can purchase it has an explosives license and hopefully knows better), but once it has aged enough it could potentially be set off by poking it with a stick. More modern explosives like TNT don't break down quite as dramatically, and in certain conditions TNT can even be rendered inert, but given unknown environmental factors any improperly stored explosives should be treated as potentially ready to go off if they are poked gently. That said, dad definitely did dispose of the majority of the old explosives simply by burning them, sometimes in place with the fire department on site if they couldn't be safely moved. The only buildings he had to set off the old explosives in were outbuildings in remote areas, where they had been left alone for a very long time. One of the structures, he was able to see a date stamp of 1918 on the wooden crate of dynamite leaking raw nitroglycerin.
Wild, that they’re still finding these almost 70 years later. There used to be a British series about finding unexploded bombs that was shown on PBS in the 80s or 90s called Danger: UXB about the teams that would defuse the unexploded bombs that would be found in England.
Here in Germany, all kinds of unexploded crap from WW2 is quite routinely found, and not just during building/renovations.
I heard in one documentary following the defusing/safe detonation of one of these that the "KBD" (one of the shorthands for the civilian ordinance disposal services) is estimated to have to work in this field for at least several decades considering the (potential) amount of explosives still hidden in the ground and water. Especially the water is another hot topic since after WW2 the Allies just dumped huge amounts of explosive ordinance and chemical weapons into the North and Baltic Seas which are slowly corroding under the water and releasing their toxic innards into the ecosystem(s).
A bunch of people employed by the ordinance disposal service have died doing their work over the years (relevant portion cited):
"Despite a professional and extremely cautious approach, deadly accidents caused by uncontrolled explosions occur time and again when defusing bombs. In the years 2000 to 2010, eight explosive ordnance clearance personnel were killed in action, [11] three of them alone in the detonation of a 500 kg Allied bomb on June 2, 2010 in Göttingen." -- https://de-m-wikipedia-org.translate.goog/wiki/Kampfmittelr%...
In the part of my city that I live in, they find, on average, about one bomb per year that necessitates an evacuation so it can be defused. Usually, these are found during construction work.
There is forest not far away from my parents home (central Poland) where people were constantly finding unexploded bombs. Finally, in 2012 a team was hired to clean it. It took them 9 months and they found "tens of thousands" of missiles, bombs, munitions etc.
If you are into First World War memorabilia sometimes you don't even need metal detector to find shrapnel balls in local forests if you know where to look.
Makes one wonder how much of it has found its way into illicit hands. Yes, it's more dangerous to the owner than to any target at this point, but if you know what you're doing it could be a source of explosives that is otherwise completely untraceable.
I think it would be more cost and time-effective to just make explosives than go around searching for them, hoping they don't blow up when you dig them out, then concealing them and bringing them back to wherever your base of operations is. Explosives are (somewhat) easy to make, it is setting them off reliably without blowing yourself up that is difficult.
I’d imagine most people with the knowledge to safely handle these types of explosives already have access to modern weapons grade stuff (black market munitions, etc.). For your run of the mill domestic terrorist type it really isn’t that hard to make explosives (fertilizer and diesel fuel), so probably not worth the risk of messing with unstable 100 year old bombs.
I stayed in Verdun for a couple of nights on a trip through France last year. I explored the forest a bit, and noticed there are two kinds of rocks on the ground: White, chalky ones and brown ones. The brown ones are fragments of artillery shells.
It's a reasonably regular thing here in France. It's the sort of thing they'll find anytime there's a new building going up with underground parking beneath it - the contractor digs, finds a bomb, the army cordons off the quartier for a few hours and sorts it out. Makes the local news but mainly because it either obstructs traffic or is close to a school that needs to shut for the morning.
What does this mean ? Someone is operating a backhoe and there is a loud KLUNK and the operator looks at what it hit and says to him/herself jeez I'm lucky to still be alive ?
Most of the time, the lawsuits for digging up someone's fiber optic cable or natgas line are so staggering that there are various "free" one-call services that mark buried objects. The public utilities all pool resources to fund it, so it's free in the sense that your utility bills pay for it. I know a guy who had a gig doing that and in addition to locate devices that are kind of like a giant telco wire toner, they do indeed sometimes walk around with a literal metal detector. Doesn't work very well on terracotta sewer pipe but those generally collapse in a couple decades as I've found out the hard way.
Anyway, yeah, a dude with a metal detector walking around with a map of buried pipes in one hand saying "that's odd there's not supposed to be a pipe here"...
Yes. I think it’s more dangerous for farmers, though. They have weaker machinery. Also, in parts of Belgium and France, it’s so common to find stuff that they carry small explosives, including mustard gas grenades from World War One, to the side of the road for later pickup by bomb disposal experts (https://en.wikipedia.org/wiki/Iron_harvest)
Most bombs are found by actively surveying the site, often using old aerial photography. But random finds happen and sometimes with deadly consequences. In 2014 a bomb exploded during earth works, the backhoe operator was killed https://www.deutschlandfunk.de/unfall-baggerfahrer-bei-bombe...
I guess it is something like that, but don't know for sure. I live in a major urban area so if they find an unexploded bomb it has probably been built over a couple of times since it was originally dropped. The most recent near me (about 800 meters away) was in 2021 and the most interesting thing about it for me was that it was a US bomb, not a German one.
Pretty much, although in that case they would indeed be very lucky to not set it off. I guess it is more likely that they find it when they put down the soil they just excavated. I would like to be educated about this, but I feel they should pretty much expect these things and check with a metal detector before excavating the next layer of ground.
Parts of northeastern France are still off limits because of stuff left over from the First World War. Official estimates are that, at the current rate of clean-up, it will take somewhere between 300 and 700 years to clear the area completely: https://en.wikipedia.org/wiki/Zone_Rouge
My German town of 70000 inhabitants has a WW2 bomb evacuation roughly every 4 years, in my experience.
Many hundred to a few thousand people have to leave their houses, police and other emergency services from the whole state come into town, the whole day or evening is full of sirens.
The local paper is running articles about the two or three bomb specialists as if they were old friends you haven't seen for a while.
Also when you're building the permit explicitly states that anything found that looks like munitions must be left alone and the town's crisis center be informed immediately. Around here (but that's because the area was heavily bombed) they routinely check aerial photos before issuing the permit. They even ask old people who lived around here if they remember bombs falling around the plot that's about to be built on.
In Ypres, Belgium, there are still unexploded shells from the first world war being unearthed. Those are now more than 100 years old. Farmers there know not to plough certain areas of their land.
It's so common there that you just leave your unexploded munitions at your gate for a pick-up.
From Wikipedia ..
> In Belgium, Dovo, the country's bomb disposal unit, recovers between 150 and 200 tons of unexploded bombs each year. Over 20 members of the unit have been killed since it was formed in 1919
Many more of the public (farmers typically) have been killed due to the "iron harvest"
It’s relatively common in the UK. According to this BBC article[0] the Ministry of Defence deal with about 60 a year. There was one washed up on the beach last month in Brighton near me[1].
It’s very common in Germany. August last year, Berlins disposal site caught fire with 25 tons of not disposed ammunition on the site. In winter, they blow up old ammunition every week - they stop for the summer due to fire hazard.
It was about 50 yards from my bedroom window when I was at university 20 years ago. Wierd to think what could be sat in the field opposite my house right now.
Bombing wasn't all that accurate back then. No GPS- or laser-guided ammunition was available yet. Missiles were quite experimental still and mostly used by fighter-bombers. Night bombing adds its own difficulties. Also, both sides had to deal with enemy air defense that was quite state of the art, therefore they could rarely take their leisure time to target well.
I believe the CEP (Circular Error Probable - the area near the aiming point the bomb was likely to hit with a 50% probability) was something like 5 miles for night-time high-altitude bombing during WW2.
A cursory search of WW2 airplanes, I am finding plenty of bombers that could operate at 500+mph (probably not when fully laden, but still). Targeting anything when going at that speed by little more than eye is still hugely impressive.
I'm in datacenter business and I'm managing couple of facilities around EMEA.
German (Frankfurt and Berlin) sites are notorious for sending out warnings that WW2 bombs were found in vicinity and defuse plans.
Having hundreds of kilos heavy bombs near data centers makes my nerves tense.
And I can only imagine how many are still to be found
It's not all that strange, a bomb that does not go off will bury itself deep in the terrain, you need to go looking for them somewhere between 8 and 12 meters deep!
The expectations are that for the areas in NL where there was a lot of bombing that it will take another 125 years before they'll be able to declare the job done.
Think about what this means for Ukraine where shells from both sides all land on Ukraine soil. The current front line is going to be a disaster area for decades.
It depends, shells won't go nearly as deep as a heavy aircraft bomb. And most of the Netherlands terrain is dry swamp. I don't think the same applies for other terrain types especially with a heavy rock layer.
So I don't think it'll be quite as bad. Mines on the other hand would be a worse problem there.
The fact that they don't go as deep makes it a different problem, not one that is less bad per-se. Aircraft bombs that sit 10 meters or more underground take an effort to reach, but that also means that they are relatively safe until you go looking for them. Unexploded artillery shells are shallow enough that regular work such as agriculture will turn them up and that means that lots of farmers will be at risk of their lives for a long time to come without an effort to clear their fields. Mines are extremely bad because they are usually hard to detect depending on what they are made of and can be set off by even the lightest vehicles (and even pedestrians).
In Germany WW2 bombs continue to go off at a rate of 1/year. We have to thank the Lord Lindemann and Bomber Harris for that - the two promoted the frankly idiotic idea of carpet bombing cities instead of armament factories, hoping that the population would overthrow Hitler. That at least was the official line.
What these two war criminals did was mix delayed fuze explosive bombs in with the regular incendiary and explosive load. The idea was to kill firefighters and interfere with the firefighting effort after a bombing run. Some of these delayed fuzes worked too well and instead of 4 hours after release they go off after 70 or 80 years.
> What these two war criminals did was mix delayed fuze explosive bombs in with the regular incendiary and explosive load
Even more hardcore than this, it was a common practice (e.g. it was done at Dresden) to do a second bomb run a couple of hours after the initial one, to hit the first responders. Of course none of that shit meaningfully impacted the duration of the war.
Funnily the Russians are doing the same now in Ukraine. People never learn, do they?
Its standard practice with insurgents and paramilitaries like FARC and the CIA drone squads in the oughties. One strike to hurt people and light fires, another a few minutes later to kill the first responders.
We still have several a year involving sudden neighborhood evacuations in the Nuremberg area, and I expect my son, age 2, will still be dealing with this when he’s an old man if he stays anywhere in Germany.
It’s especially chaotic when one is found close enough to stop traffic to and from the main train station, which is also a nexus for the subways.
I remember a WW1 naval mine being washed up on the beach we went to when I was a child, and being evacuated away into the town centre. Sort of leaves a memorable event when your 'day at the beach' is ruined like that.
It was mid-70s, so Danger:UXB was still a couple of years away.
Few years ago, in a town not far from Venice, digging a new road underpass, they found a completely unknown underground warehouse filled with nazi arms.
That was quite exceptional, but still nowadays WW2 bombs are found all over Italy, millions were dropped.
Great series. Towards the end they were showing the early experiments with steaming high explosive from bombs too risky to move. I guess this “burn the explosive out” method is the current evolution of that.
They had to dredge Portsmouth Harbour to accommodate the new QE2-class aircraft carriers.
Almost every week it seemed work had to stop and the area evacuated because they kept pulling up unexploded ordnance, Portsmouth being the home of the Navy and therefore very heavily bombed during WW2.
I loved that show when I was a kid. There is a ropey version floating around on the ocean waiting for a curious buccaneer to pick up. It still holds up.
Ever been to Sheerness? they reckon it'll do two million pounds worth...
...of improvements.
Seriously though, they more than know and check, it's carefully marked with large conspicuous buoys as well as constantly monitored in case someone fiddles with it and there are some pretty big, fast police RIBs round there. (had a nice friendly chat with them when they wondered if I was a drug smuggler.) Apparently they're cutting off the rusting masts (above water) sometime soon to reduce risk further. But there is not much that sensibly can be done to actually remove it, and there may not be much of it left that can actually go up.
Buried bombs that nobody knows are there are far more worrying... and the Germans have that problem rather worse than Britain does.
At risk of personally identifying information... I guess I did volunteer this one.
I knew not many people pick a day in mid December to go sailing. I didn't know I'd be the only one out, the day they were doing a massive drugs bust. They clearly thought no real pleasure sailor would be there. Fortunately I am obviously a harmless WAFI* and the appearance of my kid's cheery grin in the companionway was enough to convince them. (Bringing them up hardy, you see)
They probably also realised that with their hundreds of horsepower it's not like my beloved 4KSB* is a credible getaway vehicle.
Sorry, can't think of any more funny ones right now. 4KSB is a Sailing Anarchy-ism; the same kind of boat is for some reason a MAB in the UK - a Manky Auld Boat. I take exception to that one.
It still happens from time to time in Germany. To my knowledge the last fatality was an operator of an excavator in 2014.[1] It is disturbing that one can still become a victim of WW2 in a certain sense.
The piece of shrapnel the size of a bus that lands on the road gives you a sense of the scale and is horrifying. At first I was like "they let someone drive by that site while diffusing?!?
I think that was part of the containment around it. The bomb itself is an SC250, which is less than 2m long. But it definitely gives an idea of the power of the explosion it caused.
I'm assuming you mean American Civil War... and I wouldn't rush to call it done, some of those sieges involved a lot of big ammunition and there might be more out there. Impressive it was dry enough to go up, though, gunpowder soaks up moisture fairly enthusiastically.
In fact, they often just build a bunker and do a controlled detonation - the bunker directs the explosion forces upwards, where they don't harm anything. Not sure why they decided to defuse this one.
When it is easy, they defuse it. But usually it is all rust, so controlled demolition is the preferred way to go and usually always done, unless it is hard because of sensible surroundings. But then the bomb gets transported.
Fortunately we have much better technology to help locate and remove or destroy unexploded ordinance. We also have the benefit of satellite surveillance to help determine where all this ordinance landed so that even if later operations change the landscape we can see where impacts occurred at each stage and have a real clue about where we should focus. It will be a huge task but it will be made more manageable by the improvement in the tools utilized today versus after previous conflicts.
there is a possible urban myth (no one seems sure if it is a myth or not) that the "gate guardian" at RAF Scampton in lincolnshire consisted not only of a lancaster bomber (i can confirm that - i went to school under one of the bomber's wings) but also a tallboy and a grandslam earthquake bomb (can also confirm - pretty sure there was one of each). the latter 10 tons gross weight if filled with explosive. which in this instance, it may have been.
what i can't confirm, and nobody really seems to know is whether this myth is true. if it was, and if it had gone off it would easily have levelled this nuclear bomber base (me included) and much of the surroundings, with possibly interesting consequences at the height of the cold war.
I'm leaning towards no... because I have been lucky enough to go behind the scenes at Scampton. Scampton is where the dambusters flew from. Outside of Guy Gibson's (Dambusters CO) office is the grave of his dog named N*** that was killed the day before the dambusters raid. Next to it is an 'Upkeep' bouncing bomb mounted on an apparatus that allows you to spin it. Opposite are the 'Tallboy' and 'Grandslam' bombs which I strongly suspect are the ones from outside the gate. I also seriously doubt what the article suggests the damage of a donation would be. Lincoln cathedral is nearly 5 miles from the gate at Scampton!
I'm leaning towards "no" without evidence because it's a good tall tale.
Aside: A playground park sand pit used to contain a decommissioned FJ (-2 or -3) Fury. No ordinance or armaments though: live, dead, or Schrödinger. In the quest to cover kids in bubblewrap, of course it was replaced with a boring, cookie-cutter playground.
i tend to agree, but you can never discount the stupidity of the "bloody military mind" - a favourite curse word of my mum when my dad, a pilot, was off on exciting detachments and she was stuck in the middle of a lincolnshire wilderness with three kids.
The issue is settled now. Germany paid huge war reparations after WWII until the 1990s.
Apart from that, many of these explosives are malfunctioning bombs that were supposed to go off when firefighters and rescue personell are at the site. Such devices are pure malice; the defense argument can't justify them.
You can't randomly levy all sorts of minor nuisance onto somebody after they've conceded and signed a bunch of treaties largely drafted by the winning side meant to settle this. That's just a great way to self-sabotage your diplomatic reputation.
But there is (or rather was) an greater argument, of not wasting anymore time, with historic fights over and over again and rather move on and look forward.
All the great conflicts are getting solved that way and not with bean counting.
This was while they were attempting to disarm the bomb using the technique of "slowly burning the explosive", which in my obviously completely inexpert opinion, I wouldn't have recommended.
I would assume that the explosive was TNT. TNT actually takes some effort to detonate; this is why even artillery shells can be filled with it, an not explode during firing. TNT can also burn safely e.g if thrown into a fire in small amounts; you likely can even make a candle out of it.
The bomb likely had another, undetected detonator which was triggered, and it produced enough of a shock wave to make the TNT explode.
> The bomb likely had another, undetected detonator
That would be really poor bomb design. Bombs are designed to be stored inert near the airstrip, mounted to staged aircraft and armed quickly by inserting a primer/detonator. There would be one and only one per bomb. The detonator would certainly be removed first before trying to burn out.
Explosives usually become more unstable over time, sometimes forming pockets of primary explosives, which can detonate the bomb. See my sibling comment.
Edit: I'm completely mistaken! Some bombs in fact have multiple fuse pockets, so presumably, multiple fuses. Nonetheless, even with all fuses removed, UXB can still go off during disposal.
Well, poor or not, they did it, I found the American TM for german bombs of that era printed in the 50s and the SC250 definitely has a forward and after fuze pocket. Took 5, 17, 50, or 57 series fuzes.
Its wild that all this stuff from decades ago is online. You get used to not having any historical data about, well, historical events.
The type 17 fuze was a clockwork that could go 1.5 to 80 hours after landing. I could imagine something like that getting jarred into working again after a few decades...
Thanks for the correction! Yeah, I did some more digging and there are in fact some wacky designs. The single-fusing-element is more dominant in modern designs, but war is a crazy place.
The Germans would sometimes use a timed detonator on their bombs, intended to kill emergency services personnel who moved in after the raid and were fighting fires, aiding the wounded, etc. If you haven't seen it, the show "Danger UXB" from the early 80's is good.
You jest, but I believe some of these incidents have been caused by some sort of delay mechanism which gets stuck, until one day it is dug up or corrodes enough to unstick, at which point it goes off.
After I clicked reply and went to do a chore I thought to myself "I didn't talk about how it's been almost 80 years and it's unlikely to have been a timer." Doh.
The British just sent two waves of bombers one a few hours after the first to kill off the ambulances and firefighters. Seems like the Germans once again beat the British at their own disgusting tactics with better technology.
Also do you have a source other than a post-war tv show? Im getting a lot of unrelated search results when trying to confirm that timed fuses were used this way. Typically timed fuses were used to make the bomb explode before reaching the ground so it wouldn't just blow dirt into the air but would actually collapse lots of roofs etc. mis-set timers could hurt rescue personnel but i havent heard that that was even intended by the Germans.
These were not proximity fuses, but fuses with clockwork timers designed to delay hours or days until they exploded. This turns them into area denial weapons. Militaries use them to this day (but with modern electronics) on targets like airfields.
Early "proximity" fuses like you're talking about (not the later radar VT fuses developed by the British & Americans, first used at the Battle of the Bulge) had mechanical timers with delays of only a few seconds to account for the planned height of the aircraft when dropped. Many of the men awarded the George Cross for their UXB work encountered them after they malfunctioned (If you ever have the chance to visit the UK Imperial War Museum, it's highly recommended.)
> Seems like the Germans once again beat the British at their own disgusting tactics with better technology.
Check your timeline. The German bombing campaign against the civilian population of major British cities started in early September 1940 (mom spent many nights sheltering in the family's Anderson Shelter from the German bombs). Retaliatory bombing in occupied Europe & Germany by the British didn't begin until the next year.
I was asking for a source that those were actually used on british cities. That article sounds like bombs that were supposed tk detonate not the ‘ambulance killers’ you say were used.
>When explosive devices failed to detonate
From wikipedia:
The Royal Air Force began bombing military targets in Germany, such as docks and shipyards, in March 1940, and began targeting Berlin in August 1940.
Im sorry Churchill’s unpopular warmongering killed so many of your people.
Your commentary here and in your post above has been incredibly insightful. I was reminded of the 1967 USS Forrestal fire, when I had recalled reading that the ships captain and ordinance handlers were extremely worried about loading old bombs aboard the ship. Your explanations gave much further context to what was likely happening in that ordinance that gave those men such concern. Thanks!
> Specialists started the process by using a robot to cut the fuse and trigger at about 17:30 GMT on Thursday, but abandoned this when water from the cutting process destabilised part of the sand barrier.
> A decision was then made to switch to a slow burn technique, which was being carried out when the device exploded.
This is what we were taught on seismic crews too. It is generally okay and safe to burn sticks of dynamite (TNT) but just make sure you don't whack them really hard trying to put it out. The energy required to make it explode was supplied by a blasting cap which took a small electrical voltage to cause it to pop, roughly a half volt if I remember right (40 years ago so no guarantees.) You didn't want to disturb the blasting caps but you could toss the sticks of TNT anywhere with no consequences.
For safety while handling, many explosives need both heat and pressure to explode. Famously, soldiers in Vietnam would burn C4 for heating water. However, explosives tend to become more sensitive over time, and there's always a chance that the explosive filler in this bomb wasn't an insensitive explosive anyway. Given the chance of it exploding when burned versus exploding when jolted, it probably made sense to burn it in place
> in my obviously completely inexpert opinion, I wouldn't have recommended
I'm pretty confident they had some of the best experts on the case.
The UK has some of the best bomb-disposal minds, the IRA campaigns on the mainland during The Troubles ensured that. Just look it up on wikipedia ... double-digit number of bombs planted in some years !
Does defusing a brand new IRA bomb involve the same set of skills as defusing a decades-old Luftwaffe one? I would have thought it's a rather different problem.
IED has progressed immensely since the internet and the best bomb disposal techs are the people who'd been doing it recently and they're mostly in the middle east.
Over a thousand or about 60% of the Provisional IRA kills were British soldiers. So yea they got hit hard. I haven't seen any evidence that they actually improved their bomb disposal techniques though. The British Army kept getting successfully bombed into the 90’s.
Some explosives, like C4, can actually be safely burned. To set them off, a detonator is required. Explosives from WW2 probably have similar properties, as it makes producing and handling huge warheads a much less dangerous activity. Of course, there might always be impurities in the material that makes them behave much more unstably, both from production and because of corrosion and chemical degradation over the ~80 years that have passed.
Some context as a chemist. Most explosives require DDT (deflagration to detonation transition) in order to explode. DDT occurs when the flame front goes supersonic in the material and creates a shockwave (simplification but close enough).
Low sensitivity is desirable because you want explosives to go off on demand, not randomly. Thus, most bulk explosives can be safely burned without detonation. Primary explosives have a low DDT threshold, meaning it takes far less energy and/or confinement to DDT. Thus, you can have a small primary, sometimes a secondary booster, to set off your bulk charge. The primer can be removed/dissolved to render the weapon far safer. But not perfectly safe.
I don't know the exact composition, but it is likely a combination of TNT, and one of the hexagen/MX explosives (RDX, HMX) [1]. Luftwaffe used Trialen 105 in their 250kg bomb [2], which is TNT, RDX, and aluminum powder, so lets go with that. TNT is fairly stable, *MX are quite stable, but picrates are ornery. Over time they can break down and react with metals in the casing. Metal picrates are much closer to primaries in temperament. They are also far more shock sensitive, which is why (somewhat paradoxically) it's safer to evac and burn these old bombs out, then to try to relocate it. There are other ways in which unstable residues can be formed, not just picrates (e.g. TNT can release NOx over time and form metal nitrate or fulminate salts). You also have all the impurities from synthesis (such as DNT and mixed nitrates). Over time this forms a witches' brew of mixed nitrates that's typically much more sensitive. Sensitive, as in, workers have died when their shovel struck the bomb casing. There would not even be time for the clunk sound to make it to their ears before obliteration. Or even just...nothing [4]. Hug your loved ones, folks.
(side note: this is why if you ever find old orndance, or old bottles of certain chemicals e.g. ether, you should stop immediately and don't try to move it, just evacuate and call a hazmat team)
What most likely happened is the old bomb corroded and formed a pocket of these unstable salts, and when the flame hit it, a DDT occurred which set off the bulk charge.
This is all well known to ordnance disposal folks, hence the sandbox cover and evacuation radius. [3]
Edit: tweaked wording after some more research into bomb composition.
P.S. I updated my notes on explosive composition. Turns out WW2 US/UK favored picrate mixes far more than the Germans (who favored TNT, RDX, ammonium nitrate, and aluminum), and as a result, allied bombs from this period are much more unstable than German ones. Also note, forming unstable species isn't necessary for DDT: e.g. the Halifax and Beirut explosions were caused solely by burning ammonium nitrate. It's just much, much harder to get a pile of AN to go off than rando metal nitrate salts.
> It's just much, much harder to get a pile of AN to go off
Which is why Hezbollah is complicit in the Beirut port explosion of August 4, 2020. AN that's just sitting there for years doesn't simply explode for no reason.
There was a fire and the warehouse also contained a large amount of confiscated fireworks. Similar AN explosions have happened in several other countries too, with no resorting to conspiracy theories.
No I believe it's a common approach. Without the fuse dynamites are inert and you can burn it without exploding it, since they are actually flammable. Of course, lots of steps can go wrong like incomplete removal of the fuse.
There's a lot about explosives and explosives removal that is not obvious. Even more so because those techniques are classified both to keep other weapon designers from designing around your diffusal methods, but also to keep from elevating the "game" as it were of the public.
What method would you have used in your common sense guess? The old cut the red wire method? Chat gpt says "call the police and leave the area" as the most effective bomb diffusal method. The experts then "diffuse the bomb" as the next step. So there you go.
I'm reminded of the time I heard of the story of a US town blowing up a beached whale with TNT that didn't go as planned in high-school when we were on unit discussion the mechanisms of explosives. I think the teacher was there(?) as a kid and it...ignited...an interest in explosive engineering in him.
I do agree that I see that comment a lot on here. However that seems to be a pretty uncharitable reading of the parent comment, as it seems they were more expressing surprise that burning the explosive is a legitimate means of defusing a bomb.
There’s nothing wrong with pointing out that a standard technique for disarming a bomb seems counterintuitive to a layperson. That’s the sort of observation that fuels curiosity and interesting discussion. I don’t think the OP was suggesting that it was the wrong technique.
Whether it is or not, I would strongly recommend the OP - just like a striker who just scored a goal from a corner - immediately claim that is was 100% deliberate.
Unfortunately the best replies were usurped by a telling off from someone who comically misread my tenor, and now the whole thread has been moved from top straight to bottom, presumably as the victim of some anti-controversy algorithm. I know it's not the done thing to comment on such matters, but there's some really great posts in there that people put a lot of effort into, and now they're buried, which, dang, is a shame.