MythBusters Episode 122: Thermite vs. Ice
Air Date: May 27, 2009
Igniting a bucket full of thermite on top of a several blocks of ice will cause an explosion.
confirmed
Adam and Jamie tested this myth as shown in a viral video (with one galvanized steel bucket full of thermite on top of ten 1-pound/0.45-kilogram blocks of ice). An explosion did indeed occur, thus confirming the myth. Using more thermite and more ice resulted in a larger explosion, enough to literally rain down fire a few seconds afterward and send ice chunks flying over 150 feet (46 m). In a first for the show, however, no explanation was given for why this occurred, because there is none; while hypotheses ranging from the rapid release of hydrogen and oxygen from the vaporizing ice by the thermite to the aerosoling of the thermite itself exist, no one has been able to definitively prove exactly what happens to cause this mixture to be so volatile.
The vibrations caused by a car stereo system at full blast is enough to trigger a misfire in an SKS rifle.
busted
This myth originated from Russian gangs, who use an SKS rifle with a freesliding (as opposed to spring-activated) firing pin. Supposedly, any large vibrations, such as from a loud car stereo system, can cause the firing pin to trigger and fire off round after round at random. To test this, the Build Team “pimped their ride” with the most advanced sound system they could get, and placed several of the appropriate rifles in different areas in the car before subjecting them to several decibel and tone levels worth of sound. However, none of the guns went off. Even taking the guns for testing at a sound studio and getting a custom car specifically designed for sound system contests couldn’t produce a result.
The shock wave caused by an exploding bomb is enough to trigger a misfire in an SKS rifle.
confirmed
The Build Team tested another, similar myth from the same source, involving an exploded bomb setting off guns placed around the blast zone. This time, one of the guns did fire from the shockwave of the explosion.
Holding a hunting revolver improperly can cause your fingers to be blown off by the escaping gasses emitted when the bullets are fired.
confirmed
This myth came to the MythBusters in the form of a picture that was too graphic to show on air. After testing the handgun and noting the power of the gun’s recoil and the gasses that emitted from between the barrel and the chamber, Adam and Jamie built a pair of chicken hands to test the damage these gasses can cause to an unprotected hand. While Jamie’s less anatomically-correct hand only suffered some minor flesh damage from the gasses, Adam’s hand – specifically created to mimic the bone and joint structure of a human hand – had one finger blown almost completely off, confirming the myth.
Newer: Episode 123: Prison Escape
Older: Episode 121: Seesaw Saga
Playing with thermite. Now you boys are approaching your destinies.
June 11, 2009 at 11:08 AMWhat is the make and model (caliber) of the handgun used on episode 122?
June 12, 2009 at 9:37 AMDear Mythbusters,
June 14, 2009 at 9:46 PMWith the thermites extreem heat, could the rapid melt of ice to water to steam, with steam being the explosive force? The ice for a split second becomes a sealed contaner and the steam explodes the ice blocks
Dear Mythbusters,
June 14, 2009 at 10:03 PMI am currently watching the episode about the SKS weapons being set off by the sound system in a car. Although you did try multiple variances of bass, One thing I didn’t see you try was punch bass. Punch bass is found in most songs, and on Bass cd’s. A couple that you could try is: Bass 305, Atomic 24’s and various others. A lot of these cd’s or MP3’s are used in Bass competitions. The single hard hit of bass, multiple times (punch bass) may be just enough to set off the weapons. Just a thought from someone that deals with stereo’s, tuning, and used to do bass competitions.
Please confirm the make and model of the chicken finger handgun.. I had my thumb blown in half by a 460 s.w it looked like the same gun.
June 15, 2009 at 1:21 AMEd has a grasp on the concept but what he didn’t say was that when you make steam from the thermite at the same time with the intense heat you are splitting at a memcular level to produce the nitrogen and oxygen. I bet if you put a sniffer in the area you would see a higher result than expected. they say it burns at high temp 2887. you have al oxide, iron oxide in powder form this is the same stuff you use in welding. so at 2887 degrees fer. I am asumming complete seperation of atoms of ice in one instance ice becomes steam then splits and becomes pretty much at that temp close to plasma “total heat = large explosion”
June 15, 2009 at 5:02 AMThe reason the thermite and ice mixture exploded is because the relentless heat of the thermite superheated the ice
The ice turned from itself into steam instantaneously, with NO liquid state.
When water is superheated, and it comes into contact with a suface with ANY nucleation sites, it turns into masses of steam.
The rising steam is what gave the explosion the upward force.
The particles of the explosion came from the molten iron and aluminium oxide (The products of the thermite reaction) as well as fragments of the metal bucket
To be honest, I’m surprised you didn’t think of this, it is simple physics, and superheated water is used everyday in coal-driven electricity plants.
June 15, 2009 at 11:07 AMNickesh beat me to it, though there is always a liquid state, just so rapid it’s all but undetectable (and a factor in the violent reaction).
You can see the same result with very cold water, instead of ice. I am also surprised you guys didn’t think to try that.
It’s like when you try to put out a magnesium fire with water. Violent!
June 16, 2009 at 10:54 AMJust to let you know matches are vary powerfull explosiv I blow my right leg clean off at just below the knee with a pipe boom 4th july 1976 it was about ft long 11/2 wide with a vary short fuse a was about 30ft away when shrap metal hit me.I have a Cleg now about 70tho dollar later doing fine love your show I have a cos that could be jamei”s twin.PS Karies fine
June 17, 2009 at 1:15 AMWrex, it’s not true that there is always a liquid state. The solid can evaporate without a liquid state. The process is called “sublimation”.
June 17, 2009 at 7:17 PMI have seen this effect in a much larger scale.I use to work in an Abrasive plant.The Furnaces melted different materials to make abrasives.The melting materials were around 2000f much lower than thermite.When the furnace runs deep you get a burn out,the material cuts through the steel jacket of the furnace like butter and when it hits the water (the furnace is cooled by water)it results in a rather large explosion.All caused by the super heated material hitting the cold water or concrete.No chemical reaction needed,just hot meets cold BOOM !!!
July 2, 2009 at 2:18 PMhey guys. I was talking to a chem teacher and we hypothosized that the combanation of the thermite, the coating on the galvanized bucket, and the H2O in super heated form caused the explosion. Try it out and see if thats the case.. Have fun AND BE SAFE!!! :-)
July 30, 2009 at 2:27 AMAs an engineer in the steel industry, the answer is obvious. Whenever molten metal (steel, aluminum, etc.) engulfs water or ice it will very rapidly flash to steam. The expansion is something like 1400 times for aluminum and most likely more for steel. So, assuming 1 cubic inch of water/ice is engulfed, it would make over 1400 cubic inches of steam. The pressure inside the engulfed water would rise rapidly and be immense and looks just like an explosion from combustion. Anyone in the steel industry has witnessed this event. It isn’t something you forget.
August 10, 2009 at 7:36 PMHas anyone ever dumped ‘fresh ice’ right out of the freezer into a cup of room temp. liquid? The ice pops and cracks. Sometimes it breaks into several pieces. Maybe the sudden extreme change in temperature caused the ice to shatter which threw the thermite into the air. The airborne thermite became particulate which increased the surface area allowing rapid combustion, hence the explosion.
One more thing. I know the gentlemen that lost the end of his thumb in the revolver accident is suing the manufacturer. Is that why I can’t watch that part of the episode on youtube?
August 11, 2009 at 6:22 PMi know it is a guys prerogative to wanna blow stuff up sometimes lol. the thermite thing was cool, but it suddenly hit me while watching, what’s more scary, thermite blowing up ice, or ppl just being able to blow up ice with thermite for the sheer fun of it?
August 30, 2009 at 10:44 PMI’ve just seen the show with the SKS and think the rifles that the Ruskies used were older weapons that have been used a lot.
I have two SKS’s and one have them is now dangerous as it has converted itself from a semi-auto to a fully auto. Loading a round into the chamber can set the weapon off where it will fire three or four rounds before it jams.
I am ex- British military and have been told by a military friend that the probable cause is a worn sear or sear spring. Maybe this was the case with the Ruskies rifles.
Please feel free to come to Canada and try mine.
August 31, 2009 at 12:51 PMHi I find it interesting that free floating firing pins would be blamed for SKS firing on their own as M16s M4s C7s and C8s their Canadian variants and other assault riles have similar firing pin configuration as well I would suspect that the myth originated from a misidentification of the weapon I would think it was some for of machine gun that fires from an open bolt configuration i.e. FNs GPMG and MINIMI and PKM are belt fed with the exception of the MINIMI witch can be mag fed too they all fire full auto only. There are many other guns fire in this manor I would be interested to see if one with a damaged or well worn ser could discharge in the manor indicated in the SKS myth as I have seen one fire from a significant impact and it was in good condition so a old Warsaw pact country weapon in poor condition I think could happen plus people are notorious for misidentifying Russian and eastern European guns.
Thank You
September 3, 2009 at 9:40 PMHum, could it be possible the thermite flash heats the tiny air bubbles and that is what causes the explosion?
Tom
September 4, 2009 at 4:32 AMThermite/ ice: Not sure I buy the hydrogen/oxygen combustion or pressure related ideas, but I do remember that aluminium will burn in water. So it goes like this: the thermite ignites, vaporising the ice and creating a cloud of hot aluminium powder in steam (which then burns fast enough to create the explosion).
September 24, 2009 at 12:59 PMI wouldn’t consider the SKS “myth” busted just because it didn’t happen to those particular rifles. Some SKS’s have bad sears as a result of poor manufacturing or modification by someone who didn’t know what they were doing. If your SKS has negative hammer-sear engagement, every time the rifle gets bumped, the hammer slides a little along the sear, getting closer to the “breaking” point. Eventually, a bump or vibration will overcome the last bit of friction and the hammer will fall.
This doesn’t have anything to do with the spring on the firing pin (or lack thereof.) The spring is there to help retract the firing pin after a shot is fired. If the firing pin channel gets gummed up, the firing pin can get stuck in the forward position. When the bolt closes on a new round, the protruding firing pin hits the primer and the gun immediately fires. This is usually the cause of “full-auto” malfunctions and slam-fires, but it won’t cause the hammer to inadvertently fall.
October 25, 2009 at 4:01 AMAs caleb critcher said, putting an ice from the freezer in water can cause it to crack, sometimes violently.
What happened to me: I had a hot bowl of soup, to hot to eat. So I dropped an Ice cube into it. The ice cube “exploded”, into about 5 peices, and I had soup spread about 3 meters away from the bowl!
So I think it’s about causing stress fractures in the ice to explode.
November 9, 2009 at 7:37 PMSKS Rifle
The firing rate ( frequency) of the rifle would
be well within the range of Audio frequencies.
This would mean that the firing pin is oscillating
in its housing at that frequency.
Try attaching the rifle to a parts/materials feeder, these things can shift several hundred
tons per hour rock if you want a big one, and
try again!
Your problem was that you were expecting the air
November 14, 2009 at 4:17 PMto transmit the force.
The rifle was probably sitting on the car chassis
effectively hard coupled to the speaker.
Couple of further points.
Run the feeder at the same frequency as the rifles
fire rate.Obvious?
How far would you have to drop the rifle onto a hard surface for it to self fire?
November 15, 2009 at 12:18 AM