How to Build a Homemade Flamethrower

I built a flamethrower in my backyard. And tested it.

Author's note: This is an extremely dated article written in high school.

Flamethrowers are one of the most fascinating weapons ever created. They bring a tremendous amount of visual satisfaction. After all, with the exception of firefighters, everybody loves a big flame.

The idea is to have a combustible liquid shoot out at high velocities at a heat source (i.e. candle) using a homemade pneumatic air gun. The liquid will ignite and deflagrate in mid-air, traveling to its target and setting it on fire.

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Pneumatic air gun Flammable liquid
Candle Stupidity


The design is fairly simple.

I pressurized the airgun to a mere 10 PSI (or possibly less) and stuffed a ball of wet tissue down the barrel. This wet tissue protects the valve from the thinner and also pushes the thinner out, thus preventing any backflow.

The airgun will then be aimed at a lighted candle. The thinner, upon leaving the airgun, will ignite immediately when in contact with the flame of the candle. It continues it journey through the air while deflagrating until it reaches the target, which it will set fire to.

I had the experiment set up in my backyard. I got a cardboard soaked in water as the target placed about 2-3m away.


Shot 1:

About 30ml of thinner was used.

I also extracted the individual frames from the video for closer examination:

Shot 2:

Slightly more thinner was used, about 40-50ml. Also, I placed a cardboard next to the chair with the candle to block out the wind from extinguishing the candle.

A larger flame was produced this time.

Also, if you listen in, you can hear my mom screaming “AIYO-AIYOOO!”.

Individual frames extracted from the video:

Failed Shot:

There’s also a failed shot which ended quite terribly. 98% of the thinner that was shot out of the airgun completely missed the flame of the candle and didn’t ignite. It ended up splashing on the cardboard and all over the floor. The 2% that got ignited came flying behind, landing right into the pool of thinner, setting the backyard floor on fire. The fire spreaded fast.

I removed the audio from the video because, uh, let’s just say I wasn’t saying very nice things at that point in time.

Individual frames extracted from the video:


People learn from others’ mistakes, so should you.

Here’s a really stupid picture of me wrestling with fire…

But hey, I won in the end.

And also, fire extinguishers are important in households or you’ll end up doing something like this:

The floor was covered with soot at the end of the experiment which was insanely hard to clean off. Insanely hard.

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Derek is an adventure traveler and entrepreneur. He created the Berkeley Ridiculously Automated Dorm (BRAD), a viral YouTube hit which actually has fewer views than 10 Cutest Cat Moments. He has been featured in TIME, Forbes, CNN, BBC, The Guardian, and TechCrunch. He knows how stupid writing a third-person bio of himself can be.

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