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Episode 48: Franklin's Kite and Flatulence Myths

  • Ben Franklin's kite: busted
  • Flatulence myths:
    • You can die from the fumes of your own flatluence: busted
    • Beans and bubbly drinks increase your flatulence: confirmed
    • Matches burns up the smell of farts: busted


Flatulence Containment Unit. credit Rob Werden, used with permission

The pairing of these two myths was a terrific choice given Benjamin Franklin's essay "Fart Proudly," which gives us a vision of flatulence from one of our own founding fathers. You can buy it on Amazon.

Franklin's Kite

Myth: Ben Franklin discovered electricity by flying a kite in a thunderstorm and touching a key that had been charged up by lightning.

Building the kite

Kari, Grant and Tory wanted to build a kite to Franklin's specifications using period materials. The build team's initial materials and design was:

  • Square frame of cedar
  • Silk handkerchief for the kite material (precise size unknown, but handkerchiefs at that time were either 10"x10" or 3' x3', so they made one of each)
  • Lightning rod
  • Key
  • Twine: they tested several twines from Franklin's time and chose the one with the best conductance.

Kari tested the big kite (3' x 3') and Grant tested the small kite (10" x 10"). Neither was successful in getting a kite flying. The only life shown by either kite was when the small kite made an attempt at Tory's crotch: "These kites are dangerous." -- Tory

After their failure with kites that followed Franklin's vague specifications precisely, Kari changed the designs to use more flexible dowels and a more typical diamond shape. The updated kite shape was able to get up in the air.

Three key myth tests

  1. Key charge: could the charge from lightning have traveled from the kite, down the twine, to the key?
  2. The spark: would the key have been capable of sparking to Franklin's finger?
  3. Live or die: would Franklin have survived touching the spark?

Key charge test

They took the kite out onto the beach to test #1 and even setup a mock shelter on the beach as Franklin flew his kite through a window to stay dry.

Even though it was a clear, blue sky day, they knew that the kite should be able to build up static charge from the movement of the wind over the kite and the string. With a dry kite and string they were able to build up 10kV, which still wasn't enough to get a spark off the key. They then wet the string, which doubled the voltage and sped up the rate at which it charged up. This was still not enough to generate a spark off the key, but they were at least able to verify that the kite could build up charge: test 1 passed.

The spark test

The build team used Jamie's Van de Graaff generator to generate more voltage to see if they could get some sparks on the kite key. The Van de Graaff generator can generate 100,000 volts. They move the kite's lightning rod near the generator and were able to get tiny sparks off the key down at the other end of the kite string: test 2 passed.

The live or die test

For the final test, they built a Ben Franklin dummy with a torso and hands of ballistics gel and a skeleton of PVC pipe. They visited the PGE lightning strike test facility (previously seen in the showering during a thunderstorm myth). A heart monitor was rigged up to check whether or not 6mA of current crossed the heart (fatal).

Their initial setup stuck the kite right next to the generator as it slowly built up to the test charge of 480,000 volts. This was a bit too tough on their initial setup as the the kite string caught on fire before the full charge was reached. They changed things up so that the kite could be raised up to the generator when the fulll charge was ready.

With a wet kite string, there was a nice spark from the generator, to the kite, down the string, onto the key, and into the dummy Ben's finger. The heart monitor showed a lethal charge to Ben's heart. A real lightning bolt has a lot more charge, so it would be even less likely to survive: test 3 failed.

busted (the first two parts of Franklin's experiment are plausible -- flying a kite in a thunderstorm and having a charge travel down the string -- but it's unlikely that Franklin would have been able to touch the key)

Flatulence Myths

Deadly farts

Myth: A bean-loving man, living in a small poorly ventilated room, suffocated from his own farts.

Adam built a bathtub-based flatus (fart) catcher that trapped the exhaust in a small Flatulence Containment Unit (FCU). Rob Werden of acquired an FCU from this episode (seen here, held by Adam):


credit Rob Werden, used with permission

He also got a resin casting of Adam's head (for ballistics gel molds) and a crew cap, which you can checkout on the Mythbusters fan club message board. There are also some pretty cool replica props on his site, especially if you're a Smallville fan.

Amusingly enough, Grant issued a call on the MythBusters fan club message board for volunteers to provide "flatulence samples." Those volunteers were spared camera footage of them inside the fart catcher, but viewers were treated to the sight of a pale Adam in speedo catching his bubbles.

Finding the components of flatus

The water was too cold and Adam was unable to deliver the goods at first. "I wasted a really good one at six o' clock this morning." After a good wait, Adam bubbled up a good 13.5mL flatus and followed with several more. Adam and Jamie sent Kari with four of Adam's flatus samples to have tested at UCSF. They found that Adam's samples were mostly air -- nitrogen, oxygen, and a little bit of argon -- but there was also some methane, carbon dioxide (CO2), the smelly bits: hydrogen sulfide and methyl mercaptan.

Reaching deadly concentrations with flatus

They started with testing the carbon dioxide component, as it can be deadly in high concentrations and it was also present in larger quantities

Affects of CO2 concentrations on human health: * 2% cerebral dilation, increased blood pressure, nausea, confusion * 8% nausea and vomiting * 10% death within minutes

Largest flatulence rate they recorded in their study was 170mL/hour. Based on this rate, they pumped in eight hour's worth of flatus CO2 into a small chamber with Buster. The CO2 concentration reached 0.06%. At that rate, it would take 100 days to reach a lethal levels. Breathing causes more CO2 buildup, so they put Jamie in the chamber next and measured the change in the CO2 concentration. The levels reached 0.14% in 20 minutes and 1.28% in 4 hours. At that rate it would take 36 hours to reach deadly levels. Faster, but still unlikely.

They calculated how long it would take to reach deadly concentrations from other components of flatus:

  • Methane (deadly at 2%): 441 days
  • Hydrogen sulfide: 22 years


Do some foods lead to more flatulence?

Myth: Some foods (e.g. beans, bubbly drinks, meat) can lead to more flatulence

The gas contained in flatus can come from several sources: butt burp (i.e. swallowed air makes its way all the way through your system), gas byproducts from food.

For three days, the MythBusters kept diaries of their farting to get a good baseline for their farting: * Kari: 3 times * Jamie: 6 * Adam: 10

For the test the effect of various foods, Adam is given beans, Kari is given bubbly drinks ("oh, I hope my dentist isn't watching"), and Jamie is given meat.

After 24 hours on their new diet:

  • Kari: 5 farts
  • Jamie: 6 farts
  • Adam: 22+ farts

meat: busted

bubbly drinks, beans: confirmed

Does lighting a match dissipate the smell?

Myth: a lit match can eliminate the smell of a fart

Adam made a small, sealed chamber and they pumped it full of the smelly gases in flatus. They measured the concentration of a the gases before and after remotely setting off a match. They first pumped in hydrogen sulfide and found no change in the levels of concentration after they lit the match. They then tried the same test with methyl mercaptan and found the exact same result. Based on this test, they could already bust the fact that lighting a match consumes the smelly gases in any way, but they still wanted to see if a match masked the smell of the gases.

Lucky researcher John Hunt was brought in to be the official nose to given his own ten-point scale judgement of the smelliness of the box before and after the lighting of the match:

  • Hydrogen sulfide: 5.5 pre-match, about the same post-match
  • Methyl mercaptan: 4 pre-match, 2 post-match



Funny show! I love watching Mythbusters and I'm happy there are new episodes now because I was tired of watching the old episodes OVER and OVER!
I like this episode, especially when Adam's butt "puckers up" when he gets in the cold water. His expression was priceless!
Can't wait for more new episodes!

Hi there,

As to the 'Franklin's Kite':

The key is irrelevant - in my opinion - unless BF (and followers) did not touch the twine, string, whatever.

If he/they held/hold it the charge travelling down reaches the holding body part anyway, so the key is just irrelevant!

A better setup would be to tie the string to some 1 or 2 meters-long insulator (a 'plastic' pole or beter still one of the ~400 kV power-line insulators stuck in the ground and make some charge-trap, e.g. 'connect' the end of the string via a, say, 1 cm air-gap to some special or custom-made capacitor and perhaps measure the collected charge.

Although the fact that a 10 mm gap is breached by electric charge is enough to support the myth, even without measuring the charge or current.

Anyway, what'se the key for?

Kaeli, you're dead right, check
this page for more info.

I think the flatulence myth is not totally busted. You have never been in the same room as me after a good evening of beer, cheese, and a bit of kimchi. I have awoken many people in my time due to my smells, not just sound, and have made the air nauseating in rooms of much larger size. I think the test air sample you used could have been of limited intensity compared to what I could produce, and would be willing to offer my own samples for scientific comparison.

The composition of farts definitely varies - so if you can reach a deadly concentration in 22 days, you only need a 22 fold increased H2S content (perhaps like the one sean mentioned) to get to a toxic dose within a day. Depending on the content in "your" sample compared to the whole range of existing ones, a 100 fold increase in H2S content in the farts with "highest H2S content worldwide" does not seem so unlikely (specially with illnesses like ulcerative colitis where people often have more sulfur reducing bacteria) - that would bring down time to several hours...

I thought long about the Franklin experiment. I am sure not at all it would be lethal, although still highly dangerous. It depends entirely what Franklin was connected to (i.e. standing on).
I read 10 years ago about a girl riding on a horse on an open field. She was struck by lightning, but survived, because the ohmic resistance of the horse was far greater than hers (and thus the energy was disposed of in the horse). The horse died, and her necklace left burn marks on her throat, proving she actually was the one struck.
Similarly, Franklin might have been standing on something with a greater resistance than him.

Cool episode, Adam and Jamie thanks. We in Ukraine look at it with gusto.
There is this idea: Is it possible to hide the metal from the metal detector!
I know that if you can hide it in a different metal (forgot the name - the guy came to us he had a metal bracelet of large size and it did not react to metal detectors)