Hacker News Reader

Comment by noonespecial | Hacker News Reader

I put a little salt water in a 3 liter bottle (remember those... Shasta, baby) and melted 2 wires through the cap. I connected those to a 12 volt battery and let that cook until it was good and bulging, flipped it over and then used the firing coil from a motocycle to make a spark between the wires.

It made a much bigger boom than we had expected. I believe the hole in the ground it left was nearly 2 feet deep. I think I was 13.

View on HN

Around freshman year of college -- yes, college -- my roomate got an order of Omaha steaks. They were packed in dry ice. I took the dry ice; packed it in a two liter bottle; put in hot water; and, put the cap on. I stood there for about 10 seconds before I realized that a) there was no reason to think the force would be directed out the top like my weird cartoon original conception implied and b) it would take a lot of force to rip apart the two liter bottle.

Immediately, I threw the bottle into our bathroom tub and me and the friend that was there with me stood about 10 feet outside the door. After two or three minutes, I started feeling silly. Nothing was going to happen. About 10 seconds later, it blew up. The metal part faucet in the bathtub was bent, and the shockwave had enough force to knock me and my friend down (although, it could have just been fear) and I couldn't hear for about two hours.

This was around 2003. Not one person came by my dorm to investigate. I think if it was now, I would have been arrested. Admittedly, I was stupid, but not maliciously so.

ahh, dry ice, water and closed containers. It's a classic. I blew up stuff using this method less than a year ago.

Dry ice can be hard to acquire in some places.

Luckily liquid hydrochloric acid based drain cleaners and aluminum foil are readily available everywhere and achieve the same results.

2Al + 6HCl -> 2AlCl3 + 3H2 = Boom.

The only caveat is that it throws the unreacted acid everywhere, and it's pretty strongly exothermic, but I mean, you're building a small bomb so...yeah.

My friends and I set a tree on fire once just with some chlorine and sugar.

It was a regular ritual in my hometown... gather the boys, pitch a few dollars together and buy some chlorine from the local big box stores that sold it as pool cleaner.

If you mixed the chlorine and sugar together in a water bottle, and then later added water, it would explode with an impressive pop after a few seconds.

We were carrying a few of these bottles in a backpack one night when suddenly, I heard a hiss.

Apparently water isn't needed for a chlorine, sugar, water bomb... the jostling of the two powders together in the backpack was enough to start the reaction.

By the time my friend could get the bag off his back and up to his ear to listen for himself, one of the bottles exploded.

Said friend proceeded to throw the backpack as far as he could, as we all scattered in different directions.

We met up later, and walked home past where we had thrown the bag earlier.

All that remained was a scorched tree and a few firemen.

I think that was the last time we dabbled in that sort of "fun".

By the way, my friend's hearing is fine.

Used to use pool acid and foil in a 2 liter soda bottle. Poor the acid in the bottle, pop a crumpled rod of foil in, seal the bottle, walk away.

The foil takes a few seconds to start reacting so you have time to seal the bottle. It gets hot so the bottle starts expanding and finally pops.

One time the bottle expanded but didn't pop so after waiting for a minute or two I walked up. As soon as I touched the cap it popup off and covered me with acid. I ran to the closest house and used the hose to pour water all over me.

I'm guessing either because it was spent from reacting with the foil or because it's made for pools and not all that strong that I didn't get any burns. That was the last time i did it.

We used 2 liter bottles as the gas expansion chamber on one of our battle bots. They were good to 250 psi until some folks cut back on the amount of plastic. Then we discovered you could buy bottles headed for 'desert communities' (like Las Vegas) and those bottles had a higher pressure rating. So get your soda in Vegas kids for the most bang!

> 'desert communities' (like Las Vegas) and those bottles had a higher pressure rating.

Any theory on why?

They get hot... and pop!

Had this happen to me with plastic bottles and aluminum cans that were sitting outside on pallets at a grocery store in the summer.

Right. But you didn't do it during school.

edit: Do I really need to point out that 2 felonies for this is obviously a gross overreaction by authorities and I hope all charges are dropped? That said, if you don't agree that it was universally horrible judgement to make a drano bomb during school, then there really isn't much to discuss between us and you can carry on downvoting (although I hope none of you are in charge of my future children). my longform response: https://news.ycombinator.com/item?id=5651593

Oh, come on, having horrible judgement is the whole point of being a kid. The process of growing up and becoming an adult is all about learning and acquiring good judgement. How can you expect people to gain the judgement that comes with experience without allowing them to gain that experience by trying things, some of which will turn out to be mistakes? How are they supposed to know which things are going to be the mistakes without trying some of them and thereby learning the patterns?

I once did more or less the same thing as Ms Wilmot did, and you bet I did it during school, and I didn't even bother to tell anyone about my intentions first! I set up an apparatus under one of the fume hoods in the back of the chemistry lab, dissolved a bunch of aluminum, captured the hydrogen in a balloon, and then blew the whole thing up. It made a hell of a big bang, shattered a bunch of glassware, and startled the hell out of my lab-mates. Bad judgement? Well, yeah. Duh. But I didn't actually hurt anyone, and I sure learned something from the experience, and I'll bet that all my classmates learned something from it too, without having to deal with the embarrassment and clean-up that landed on my shoulders for being the nitwit who tried it.

Just imagine how fucked I'd have been if I'd had to face felony charges after that. My whole life might have been different, my whole software engineering career derailed before it had even started. What a stupid waste that would have been. What a stupid waste it is going to be for all of us if this idiotic treatment of Ms Wilmot is allowed to stand.

Did you read my post? I do not agree with these felony charges at all. I don't know what the reprimand should be, whether it's a lecture or 1 detention or expulsion. But I know the felony charges are wrong based on the few facts we currently have.

I did read your post, and I don't agree that any formal reprimand was necessary. What did she do that deserves punishment? She found chemistry so interesting that she went beyond her classes and came up with her own experiment, which taught her something she hadn't expected. Cool! Give her extra credit, put her in AP classes, sign her up for community college - this is exactly the kind of curiosity and independent initiative we need to encourage, not punish.

I think that was gavinlynch's point: there's got to be some kind of discipline, but a felony is insane. And by discipline, I'd imagine something like what happened to you would be reasonable.

"Ok, someone could have gotten hurt. Be more careful next time, and now clean up your mess!" With the severity of the lecture following the actual damage.

Kids should be encouraged to involve themselves with the immensely powerful forces so easily available today - but they've got to fear it (as in respect it). They need to know how destructive it can be, and then _harness that_. That's my $0.02 on it.

In the abstract, the severity of the lecture should not necessarily follow the actual damage - sometimes it should follow the potential for damage, perhaps? For instance, when I was a kid, I ran out into the road to chase a ball. A car stopped about 1 meter from me. Nobody and nothing was hurt (unless you count terrifying the driver and my mother on the sidewalk watching). Was I in trouble? Hell yes. If my mother had said 'well, nobody was hurt, no problem' then how was I supposed to learn how stupid it was?

Yup, you're right. In industry, that's called a near miss. It's treated with the motions as though you were hit by that car, but none of the consequences are enacted, since nothing in fact happened (YMMV). Basically, it's a freebie: lessons are learned without anyone getting hurt, which is about as good as it gets.

Near misses must be analysed and acted upon to be a useful force in accident or disaster prevention. Such actions can include changes to the facility, changes to protocol, but also educating or punishing workers.

As an example: Misconduct causing a near miss, such as smoking or using open fire near chemical storage, is grounds for instant dismissal, even in the "socialist" countries of NW Europe.

My junior high science teacher would regularly fill a two liter bottle (with the base removed) with hydrogen generated by magnesium tablets in hydrochloric acid, then ignite the mixture by placing a match above a hole in the lid. During school. My high school physics teacher did something similar with gas from the countertop outlets and a coffee can.

Cool story. But you're talking about an official-, adult-, teacher-sanctioned event. Big difference. And to my main point: children literally don't have the neural capacity to make the judgement of when it is, and is not, appropriate to mix ingredients together that will make a blast of potentially concussive force :p

This much seems obvious to me.

I think people are mostly mentioning the "sanctioned" stories to avoid the potential for incriminating anyone. Besides, a mild rebellious streak might be a good thing for a scientist, kids are smarter than people give them credit, and excessive deference to authority is probably more harmful than a little curiosity gone awry. I think smart kids need to do more without asking, especially if they come from a restrictive environment that wouldn't give permission anyway.

Yes, you do need to point it out because this story is the perfect storm of naivete from HN. It sparks all the irrational nerves of the pro-science crowd with the hints of anti-science, the 'man' keeping the 'hacker' down storyline, the 'school is so structured it sucks' crowd, and definitely the anti-government group here. And we can't forget the 'Aaron Swartz didn't do anything wrong' crowd.

Sure, this story has an overzealous prosecutor looking for an easy score and to set an example, but the way people talk you'd think she was following teacher instruction in a lab and an accident happened and for some reason she's being persecuted for it.

She should've known better and done what the rest of us did - set the thing off in the forest behind the school.

The problem is the potential for felony as an adult. That's life-ruining stuff there, and people don't want to go soft on protesting that sort of severity. Without malicious intent, it's hard to rationalize it as criminal behavior, rather than

... rather than foolish recklessness. Plus a lot of us remember having far fewer rules, like complaining about not being able to bring knives to school (talked my way out of losing my multitool in high school). People feel strongly on What's-the-World-Coming-To topics, so expect some passion. It'd be a bit worrying if we didn't see it.

I strongly disagree. Its much better that kids do this during school, than trying to sneak around some kids backyard when the parents are out.

Say that all our fears come to true and something do go wrong and a kid get caught in the blast. If its in school, there are adults in ear shot with knowledge and tools to try handle the situation, and the kid won't just lay there and bleed out while his friends freak out while thinking about the consequences.

You can't prevent children from sometimes having a horrible judgement. You can however give them a safe place.

You can however give them a safe place.

Trying to give a "safe" place is, unfortunately, part of the problem. Instead of it being a place where kids can be helped if they get hurt, it has morphed into a (impossible) place where kids can't get hurt. Then, if something shatters that illusion, it's "off with her head!"

Blew tons of stuff up when I was in middle school. Didn't blow anything up at school, as I didn't want to, you know, get in trouble.

Okay, if you want to be pedantic about it ... Kiera didn't do her experiment "during school" either. It was 7am.

No. I have no desire to be pedantic about it. That's rather boring and lazy from an intellectual perspective.

I was playing with electrolysis a lot when I was 8-9. Probably just as well I didn't think to capture the hydrogen and blow it as I'm not sure my parents would have appreciated explosions in my room.

I'm not quite sure why I wouldn't have gon there - whether I just thought it too risky, or didn't realize the possibilities. I did have a series of books titled something like "hobby books for boys" my dad got in the early 60's when he was a kid that included a lot of chemistry covering various ways to make home-made fireworks and blow stuff up, which were all decidedly not considered all that acceptable to publish any more when I got them in the 80's, and I believe that's where I got my inspiration to play with electrolysis (my chemistry equipment was all originally my dads from the 60's too...).

I did instead have great fun covering one of my moms silver spoons with a nice layer of lead instead after using it to stir the brine, though. Not popular. I did suggest to her that I could probably fix it by using the spoon as one of the electrodes, but she wouldn't listen.

> 3 liter bottle (remember those... Shasta, baby)

Sometimes store-brand colas will still have 3-liter bottles. They are pretty good for bicycle-pump/bottle rockets, if anyone is interested in that sort of thing.

Make sure the mouth of the bottle is the proper size for your pump assembly. Sometimes 3L bottles have extra wide mouths.

You know what's more awesome?

Baggie bombs. The Oxy-Acetylene mixture for cutting steel, fill a ziploc bag with it. Add a few inches of newspaper, light it, run.

My uncle did this with trash bags. Big boom.

I did as well (50:50 with oxygen), ignited with a shot from a roman candle. Close enough to knock me over when I was 14. Realized how fucking stupid it was when I thought about static electricity and trash bags....

> static electricity

My dad did bag bombs in his twenties. He was worried about them exploding while he handeled them, so he put on wool mittens to protect the hands...

My chemistry teacher did this with hydrogen and oxygen inside of the classroom. It was one of those "desk waste basket" trash bags rather than a proper 50-galloner but even so it was so loud I was surprised the windows didn't blow out. I think she stuck with party balloons for that demonstration from then on.

Empty soda or beer cans full of oxygen and acetylene, yee haw. It sends the can tens of feet into the air, makes a loud bang like a gunshot, and makes grown men giggle like little girls.

It works even better with punching bag balloons.

I'm calling bullshit. I did that many times and never blew any significant hole in the ground (though because of impatience I started using 220V -- not a great idea). Yes it makes a loud boom, but a 2 foot hole no way.

The joy of being 12/13 is that you're still in that cusp between child and semi-adult. You've got enough motor skills and knowledge to be dangerous, but still have the childlike sense of awe that can make things look significantly larger than they are!

> still have the childlike sense of awe that can make things look significantly larger than they are!

Considering some of the fishermen[0] I know, that one never goes away.

[0] and guys I subsequently shared a locker room with

I agree. Though only if he used a plastic bottle. My father and I did this when I was in middle school. He (stupidly) held it in his hand. All it did was make a very loud boom, and not a two foot hole in his arm.

1) Your 220 made mostly steam and little browns gas.

2) We had partially buried the bottle before setting it off.

Certainly, that experiment didn't last more than a tenth of a second. Lighting a 3L bottle produces about 20kJ if my calculation is correct, so if you bury the bottle in sand or other loose soil I can see how it can move that, but well then most of the hole is because you dug it. If you have a bottle full you can safely light that with the cap off while holding the bottle in your hand, though I wouldn't advise doing the same with the cap on (you certainly won't lose your hand or anything, but it may be painful).

For the people wondering, here is a video:

http://www.youtube.com/watch?v=HmcaC0vxaSo

Interesting. Considering we never took the cap off and lit it off with the spark, wouldn't the amount of energy in the bottle go up with the pressure? Some people were saying here that a 3 liter might take as much as 250psi. We waited until the bottle was visibly distended. How would the calculation vary with pressure? I'd be interested to know the best(worst?) case scenario!

> Considering we never took the cap off and lit it off with the spark, wouldn't the amount of energy in the bottle go up with the pressure?

I have been playing a bit with a potato/hairspray cannon. If you don't have a good seal (that's why you use a potato), you get no boom. I tried to shoot snow, but it would just go hsssst.

I'm thinking the initial combustion raises the pressure enough for the fuel mixture to detonate, and if the seal is't good enough, the fuel will just burn gradually.

The calculation is already best/worst case. I simply calculated the enthalpy of 3 liters of the mixture. The energy due to the pressure buildup is negligible. If you didn't make sure that there is no air in the bottle, then the energy would in fact be considerably lower simply because then the bottle is mostly air (the way to make sure is by submerging and filling the bottle with water and wait until the bottle is completely filled with gas, and then closing the cap under water).

BTW, speaking of pressure it's unfortunate that these days the soda bottles are so thin & weak, some can't even stand 5 bar anymore, they used to be a lot thicker and stronger.

Elegant. Particularly for thirteen.

Reply on news.ycombinator.com