Dallying with Explosives

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This page last updated on 04/17/2017.

Copyright 2001-2017 by Russ Meyer


Growing up, I had a number of chemistry sets.  I went through most of the experiments in the books, then struck out on my own.  I bought all sorts of chemicals and had a blast fooling with various combinations.  I even managed to duplicate some everyday household items, like Comet cleanser, by reading the list of ingredients on the can.  I had to substitute a few chemicals and tinker with the ratios, but would usually end up pretty close.  It is really amazing how much can be done with just a few simple chemicals.  This fascination with chemistry eventually led me to dabble in chemistry of the explosive variety.
 

Hydrogen Balloons

One day when I was in 7th grade, I noticed a couple of next door neighbor boys hunched over a pop bottle with a balloon affixed to the top.  Wondering what was so captivating about this, I wandered over for a closer look.  The bottle was half full of water which was fizzing like crazy giving off some kind of gas.  The balloon rapidly filled.  The kids removed the balloon from the bottle, tied it off, and let it go.  It shot up into the air where the wind caught it and swept it away!  After a couple of minutes, it was lost to sight far up in the sky.  Well, this was a revelation.  I had to try to duplicate it.

After some trial and error, I figured it out.  Take a pop bottle and fill it half full of water.  Mix in 1 or 2 tablespoons of lye (you can get lye at the grocery store).  Crumple up 3 or 4 wads of tin foil...crumple them into a long tubular shape so they'll fit through the neck of the pop bottle.  Get a penny balloon (one of the little ones) and tie a loose granny knot around the neck of the balloon...don't pull the knot tight, you'll do that later.  Now, drop all the tin foil wads into the pop bottle and rapidly slip the balloon onto the bottle opening.  You may have to hold the balloon on the bottle with your fingers.  A reaction will occur in the bottle releasing hydrogen.  The reaction is very vigorous and exothermic...that's why you want to use a glass bottle, not a plastic one.  The balloon will inflate rapidly.  When you think it's full enough, pull the knot tight and the balloon will pop off the bottle.  Now trim away the excess string and the nipple of the balloon.  You can let it go and it will float away.

Molecular hydrogen is so small that in about 5-10 minutes a lot will diffuse through the walls of the balloon and be lost.  Because of this, they don't float long.  Nevertheless, there are all kinds of interesting things you can do with hydrogen balloons.  Hydrogen is highly flammable, and will explode in a ball of yellow flame if ignited.  It's really entertaining to make aerial explosions with the balloons.  A good way to do this is by affixing a flammable string to the balloon, lighting it, then letting it go.  As the balloon floats away, the string burns down and ignites the hydrogen.  This makes a really great yellow fireball and concussion.  You can make a good flammable string by cracking all the wax off a birthday candle, using only the wax impregnated wick.  Use a small piece of tape to affix the wick to the balloon.  As kids, we used to put bugs and stuff in the balloon, just to make it more entertaining.  Hours of fun.  The quantity of hydrogen in the balloon isn't enough to cause serious damage.  We used to hold them in our hands and light them.  The blast is enough to singe the hair off the back of your forearm but that's about it.  It doesn't really hurt, but it's startling.  Even if it blew up in your face, it would probably only singe your hair.  The effect of the yellow fireballs is really great at night.  Try it!

The final culmination of the development of hydrogen balloon technology came in college.  It was my Sophomore year at Washington State University.  A demonstration of the flammability of hydrogen in my inorganic chemistry class brought back all sorts of warm memories of the fabulous yellow fireballs of my youth.  So much fun!

I began wondering what it would be like to ignite a really large quantity of hydrogen.  A weather balloon full of the stuff mixed with an appropriate amount of oxygen would create an enormous fireball and concussion.  Wow, that would be so interesting.  Heck, there was no reason I couldn't try it myself, after all, I could easily generate copious amounts of hydrogen gas using the lye and tinfoil method.  That's basically how they generated hydrogen for civil war era observation balloons.  They used a huge oak barrel, iron filings, and sulfuric acid, but the principle was the same.  All I wanted to do was fill an 8 foot diameter weather balloon.  That sounded doable.  I set out to attempt the feat.

There were a few problems I had to overcome.  Hydrogen diffuses so fast through plastic membranes that the entire volume of gas would have to be generated in less than 10 minutes.  That meant I'd need to keep a large quantity of the reaction going for some time.  I decided to use 6 large glass jugs with valves on them.  When the reactants in one jug started burning out, I could close the valve, disconnect the jug, fill it with fresh reactants, and plug it back in.  Meanwhile, the reactions in the other 5 jugs would keep cranking.  I would just keep working, swapping the jugs continuously for 5-10 minutes.  Because the reaction releases so much heat, I needed a way to cool the jugs so they wouldn't crack and would be cool enough to handle.  I decided to immerse the jugs in a wash tub of cold water.  The heat of reaction vaporizes some water, so I needed some way to remove the water vapor before pumping the hydrogen into the balloon.  I didn't want a half gallon of water sloshing around inside of it.  I decided to use a series of glass jugs immersed in cold water as a big condenser.  I planned to use a pond near my apartment as the source of cooling water.  My final set up looked like this:

    

There was one other problem...how to ignite this beast.  An 8 foot diameter weather balloon can contain a bit over 250 ft3 of hydrogen.  The heat flash from the explosion would be significant, and I didn't want to be anywhere near it.  It seemed like the best thing would be to just let the thing float way up into the air before igniting.  This would have the fringe benefit of making the blast visible all over town.  It would also make it difficult for the police to find the perpetrator, just in case someone took a severe dislike to my little experiment.  I could use a burning wax impregnated string, just like my little balloons, but I was afraid to get anywhere near that much hydrogen with an open flame.  These little "wicks" also had a tendency to blow out as the balloon rose, especially if it ascended quickly.  It would take a lot of effort to fill an entire weather balloon, and I would hate to waste all that work just because my "wick" blew out.  I decided to build a little electronic ignition timer using a 9 volt battery, a 555 one-shot, and several rocket motor igniters.  I could set it to go off after a few minutes, after the balloon had floated up into the sky, far away from anyone.  The only problem was when the balloon exploded, the timer package would fall to the ground and could cause damage or hurt someone.  I planned to hang the electronic timer from a parachute made of light cloth, then suspend the whole works by a string tied to the balloon.  The parachute would have to be separated from the balloon a pretty good distance to prevent the heat flash from burning the parachute.  I didn't really know how big the fireball could get.  A little balloon about 4 inches in diameter can create a fireball about a foot in diameter.  By analogy, 8 foot diameter weather balloon might create a fireball as big as 24 feet.  If the fireball was that big, the heat flash would probably pose a hazard for the parachute out to about 30 feet.  I decided to suspend the parachute 40 feet below the balloon (12 foot fireball radius + 20 foot heat flash margin + 8 feet for good measure).

I had some concerns about the electronic timer.  It HAD to be stable and reliable.  It could not accidentally fire the igniters early, otherwise I might be near the balloon and get mortally singed.  I incorporated a few safety features into the design.  The most important feature was remote application of power to the timer through a 75 foot cord.  I had a switch on the end of the cord to power up the timer through a latching relay.  This allowed activation of the timer from a safe distance, just in case a transient power-up glitch fired the igniters.

With the basics of the design in place, I began to assemble the parts.  I built and tested the electronic timer.  Built a multistage condenser pack and the hydrogen gas generators.  Secured a large washtub.  Constructed and tested the parachute.  Obtained several 8 foot diameter weather balloons.  I thought through and rehearsed the procedure for filling and launching the balloon.  I figured setting up, filling the balloon, and tearing everything down would take about 3 hours.  During that time, if the police drove by and saw me, it could get ugly.  That was a definite risk, but I thought, with a little luck, I could get away with it.  I was ready for an attempt.

About this time, final exams struck and I was entirely immersed in that struggle for about a month.  After finals, I looked back on the project with trepidation.  A thought had been nagging at me for some time, and the pause for finals caused me to think about it more.  Static electricity.  I was worried that all that gas rushing through plastic hoses in the hydrogen generator would cause a build-up of static charge.  If there were any kind of spark, the consequences could be disastrous.  Inevitably, there would be a lot of air trapped in the plumbing.  If there were a spark anywhere in the system, in the reaction jugs, the condensers, the tubing, the balloon, anywhere...the entire apparatus could explode.  I had to be near the thing to maintain the reaction jugs and manage filling the balloon.  I thought about inserting explosion traps in the plumbing.  The explosion traps consisted of a large jug full of water in which hydrogen gas bubbled up from the bottom, through the water, and exited the top of the jug.  If an explosion started, it would be checked at the explosion trap, preventing it from spreading to the entire apparatus.  I could also attempt to prevent a static build-up by running a grounded wire through the whole plumbing system.  I could also use copper tubing instead of plastic tubing to plumb the components together.  That would help keep everything nice and grounded.  These seemed like a good ideas, but the whole contraption was getting really expensive and complicated.  I tried to think of some way to operate the reaction remotely from a safe distance, but everything I could think of was just too complicated.

In the end, I chickened out.  I didn't want to get shredded in a gigantic explosion blowing glass shrapnel everywhere, and the apparatus would have to be significantly more complex to accommodate adequate safety measures.  It just wasn't worth the hassle and risk to see a 25 foot fireball.  Ah well...


Gunpowder

When I was in 8th grade, I discovered that traditional gunpowder only has three components:   potassium nitrate (aka salt peter), sulfur, and charcoal.  Oh man, I just had to try to duplicate that!  The sulfur and charcoal were easy to get, but the potassium nitrate was harder.  I searched high and low for a source.  One day, I was in the drug store just browsing compounds on the shelves.  Much to my surprise, I found a can of potassium nitrate!  It was meant to be used as a diuretic for horses.  Unfortunately, it only contained 10% potassium nitrate, the other 90% being inert ingredients.  I bought it and took it home.

The potassium nitrate and sulfur were already finely powdered, but I had to pulverize the charcoal.  I mixed the three components together; 2 parts potassium nitrate, 1 part sulfur, and 1 part charcoal.  I put a teaspoon of it on a piece of sheet metal and took it outside.  It immediately ignited at the touch of a match, but burned rather slowly; it took about 1 second to burn up.  Not fast enough to make an explosive, but surely fast enough to do something interesting with.

I played with the component ratios to see if I could get it to burn faster; fast enough to make an explosive.  No dice.  I'm pretty sure it was because the stuff I was using only contained 10% potassium nitrate.  If it was more concentrated, the reaction would have been more vigorous.  I found that the ratios of potassium nitrate, sulfur, and charcoal were not very important.  In fact, you could substitute powdered sugar for sulfur and the reaction would work pretty well.  I tried substituting pulverized coal for charcoal and found that the charcoal was just as good.  I later discovered the charcoal could be left out altogether with little adverse effect.

One of my little ratio experiments kind of scared me.  I made a batch using 5 measures of sulfur and 1 measure of potassium nitrate.  I ignited about 5 tablespoons of the stuff on a metal plate.  It burned pretty slowly and made a really bad smell, as you might expect with all that sulfur.  At one point I got a big lung full of the sulfurous smoke pouring off the reaction.  My lungs recoiled in horror.  It felt like they had contracted to about half their normal size inside my chest.  In an instant, I couldn't breathe at all.  I staggered back and fell to the ground.  I choked and gagged as I lay there on my back.  I was panicking a little bit because I really needed air, but my lungs just wouldn't work.  It felt like someone had socked me in the stomach real hard and knocked the wind out of me.  I couldn't get up or crawl...all I could do is lie there rolling on the ground.  Finally, after what seemed like about a minute, I could breathe a little, but only a little.  It was like trying to breathe through a straw.  I stopped thrashing about and concentrated on surviving with what little air I could suck in.  After a few more minutes, I could take shallow breaths and felt well enough to sit up.  I found a foam of slobber on my face...apparently I was foaming at the mouth for a while...sheezh!  I got up, walked very slowly into the house, and laid down for the rest of the evening.  Uuugh.

I found a good way to make fuses with potassium nitrate.  Dissolve a few tablespoons in water.  Soak some toilet paper or paper towels in the solution and set them out to dry.  After they're dry, cut the paper into strips.  These strips will burn like a fuse at about 1-3 inches per second, depending on the thickness of the paper and the concentration of potassium nitrate in the original solution.

I had a lot of fun with that homemade gun powder.  It's best use was making fuses and smoke bombs.  I'm sure some more interesting effects could be had by blending it with powdered magnesium or aluminum.  To do really interesting things, you need a source of relatively pure potassium nitrate.  Sodium nitrate would probably work pretty well too, if you could get it.

A few years after the gunpowder experiments, I read a book about Napoleon.  In preparing for a campaign, he was having trouble securing an adequate amount of gunpowder.  He ordered some of his men to make a supply of the stuff.  They had trouble getting nitrate compounds for it.  They found what seems to me a novel solution to this problem.  They stacked piles of bricks around the army's camp, and asked the men to use them as urinals for a few months.  Apparently, there are quite a bit of nitrates dissolved in urine.  When the urine soaked into the bricks and evaporated, nitrate salts were left behind.  These were scraped off and used to make gunpowder.  I know it's vulgar, but I've toyed with the idea of trying this, just to see if it would work.  You just can't easily buy more concentrated forms of potassium nitrate.  I sort of suspect that the purer forms are regulated.  Probably to explicitly keep guys like me from making explosives.  Heavy sigh...

 

Bottle Rockets

I grew up in Washington state.  Bottle rockets are banned in Washington, which caused much consternation amongst my friends and I.  One fourth of July just before my 9th grade year, I decided to try to overcome this problem.  I trekked to the local fireworks shack to observe their wares.  I was looking for anything vaguely rocket-like; something I could convert to a bottle rocket.  The only thing close were pin-wheels.  These were cardboard wheels that you tacked to a tree and lit.  Little rocket motors on the perimeter ignited and caused the pinwheel to spin really fast, throwing off a shower of sparks.  I bought a few and took them home.

I tore the pinwheels apart and separated the rocket motors and fuses, discarding the rest.  I had bought a variety of pinwheels with different size rocket motors.  I picked one of the smallest motors, taped a broom straw to it, and jammed a fuse in the end.  Outside I placed my homemade bottle rocket in a bottle and lit the fuse.  It ignited and shot out of sight.  Cool...a technology breakthrough!  I got one of the largest motors and converted it to a bottle rocket.  I lit it and stood back.  It whooshed, gushed sparks, lifted about two feet in the air and fell back on the patio.  The motor casing was just too heavy for the thrust it produced.  I took another of the larger motors and cut all the weight off the motor casing I could.  I even unwrapped a bunch of layers of paper, reducing the case thickness by half.  This helped the rocket to fly up about 5-7 feet into the air, but it was still a flop.  The only motors that would make good bottle rockets were the very smallest ones.  I kind of wonder whether the fuel in the larger motors was deliberately formulated to burn slower.  This could have been a safety thing to prevent a catastrophe if a motor casing was damaged somehow and blew up.  The larger amount of fuel would cause a bigger problem if something went wrong, so they just made it less potent to defray some liability.  It's also possible the fuel was deliberately made to burn more slowly to prevent the conversion of these things to flying rockets.  The motor casings are heavier and would have cause more damage falling out of the sky onto who knows what.

I found the small rockets worked well enough to carry a firecracker payload.  I jammed a firecracker, fuse first, into the top of the rocket.  It would take off, fly about 150 feet and ignite the firecracker; ending the flight with a pop and puff of smoke.  My friends and I taped bugs to the rockets for astronaut training.  Oh the fun!

 

Grenades

During the summer, between 9th and 10th grade, I got the idea that making some kind of hand-thrown exploding device would be really cool.  I was helping my Dad reload shotgun shells one day, and that got me to thinking.  All a shotgun shell needed was something to hit the primer and blammo!  The only problem with that was that it would scatter lead shot everywhere at potentially harmful velocities.  I could probably just removed the shot, filled the shell with more gunpowder, and put a wad in it to hold the gunpowder in place.  Yeah, that sounded like a great idea.  The only thing remaining was to figure out a way to strike the primer when the shell came down.  I thought about that a lot and never really came up with a good solution.

Mulling over the primer problem caused me to rethink the whole approach I was taking.  Suddenly, I had a flash of insight.  The main problem in reliably striking the primer is related to the geometry of the shotgun shell itself.  What if I just gave up trying to adapt the shell and custom built something that would hold the primer, powder, and a striker mechanism?  I thought about it for a few days and finally settled on something that looked like it would work.  Only household items were required, so there wouldn't be any hard to fabricate parts.  Here's what it looked like:

 

When thrown, the fins would stabilize the thing and keep the nail pointed straight ahead.  On contact with the ground (or whatever), the impact forcefully shoved the nail into the primer igniting the gunpowder.

I built one and tried it.  It worked!  When it hit the ground, it would make a big POP, blow the cap off the film can, ejecting the cap, nail, primer and conduit plug in a cool shower of parts.  Wow, that was great!  Best of all, because the explosion wasn't confined , it wouldn't damage any of the parts.  You could just reassemble the mess with new primer and powder.  I built a half dozen of them and showed my friends.  They were suitably impressed.  We all started building them.  We had a lot of fun with them for a couple of summers.

Later on, one of my friends, Bob Nelsen, discovered a way to use unaltered shotgun shells as grenades.  He simply taped a marble over the primer and chucked the thing into the air.  It would usually come down marble end first.  The marble would convey the force of impact to the primer and detonate the shell.  I was a bit alarmed that he didn't remove the shot from the shells, but it never seemed to cause any damage.  He had a lot of luck with them, but I never built any of that variety myself.