Trying To Set Things On Fire, You Know…for Science.

This video from [Just Think] caught our attention for open-flame testing of 6 different commonly used liquid fuels: Jet-A, diesel, heating oil, kerosene, avgas (100LL), and gasoline (or petrol, for our international readers). We love his low-tech approach to testing – just some mason jars and a back yard. The results are quite interesting.

He starts with testing Jet-A fuel. Yep, the same stuff you’d fill up your Boeing 737 with. We flinched for a second as he drops a match into it – then nothing happened. It’s a common misconception that jet fuel will sustain a flame by its self. It needs to be atomized to burn, as he shows in the video. He moves on to test both diesel and heating oil – making note that both are exactly same, except for color. Heating oil has a red dye added to it, to mark it “not for sale” for cars and trucks, as it’s not taxed. Neither would keep a flame.

Next up is kerosene, and it would just barely keep a flame. kerosene is commonly used as a replacement for diesel in extremely cold climates, were diesel fuel would gel and clog fuel systems. Finally, he tests avgas and gasoline. Both would sustain a flame quite well.

We think this small experiment is interesting, in that the results are kind of counter-intuitive. All these different fuels are used in different applications because of their different properties, and of course there is some really interesting science behind that, if you want to learn more.

We don’t need to tell you to be safe when working with fuels. Even though something like Jet-A fuel won’t carry a flame in a container on its own, doesn’t mean that it won’t burn aggressively when combined with other things (like clothing) and in other situations. So we’re filing this one under “don’t try this at home” – instead, sit back and enjoy the YouTube video after the break.

26 thoughts on “Trying To Set Things On Fire, You Know…for Science.

  1. Even if that hoodie is 100% cotton (which I doubt) it’s terribly dangerous to wear for fire experiments. Take it from someone who’s been trapped in burning clothing before. Nightmares forever.

    1. Trapped in burning clothing? You mean your clothes were on fire? Stop drop and roll, but it still sucks. Been a firefighter for 20 years, and I’ve only had one equipment failure and burnt the shit out of my index finger. Burns and non fire rated clothing are no fun.

  2. I don’t understand why you would think these results are ‘counterintuitive’.

    This is pretty basic chemistry: the more volatile the mixture, the more likely it is mix efficiently with the oxygen in the air and to burn, and mixtures of shorter hydrocarbons are more volatile.

    Gasoline (avgas is essentially very high octane gasoline) is composed mainly of much shorter hydrocarbons than kerosene (Jet-A is mainly purified kerosene, diesel is mainly *less* purified kerosene; modern ultra low sulfur diesel is essentially slightly dirty kerosene.) so he’s comparing two different fuels (albeit of several different grades).

    1. Almost. In terms of Jet or Diesel they are very similar in property to Kerosene however:

      Kerosene is mostly a straight chain paraffin.
      Diesel and Jet can contain a large number of impurities.

      It is not right to say that Jet-A is purified Kerosene, or that it’s cleaner than Diesel. In fact typical refinery operations will take a straight run crude oil and extract Kero and Diesel, the Kero goes via a sulphur treatment straight to Jetfuel and the Diesel then gets really heavily treated. For instance Jet fuel has a 3 orders of magnitude higher sulphur spec so if you’re refinery is sulphur lean you can actually take the sulphur out of the diesel and stick it into the Jet, the requirement however is that it doesn’t smell so it’s treated in a Merox.

      Diesel is typically a lower cut than Kero and slighly heavier, however it also is mixed with cracked products and byproducts like n-paraffins, iso-paraffins, and cyclo-paraffins and then a small amount of alkyenes are added to make it more volatile.

      Each fuel is actually very different despite comming from a very similar cut out of crude oil, it’s way more complicated than which one is “pure”.

      1. Running kerosene through a diesel engine will fuck up your injection pumps and basically seize the engine, because it doesn’t lubricate modern high pressure injection systems properly. That’s the reason for the “impurities”.

  3. Yep. This is why when we burn trash or stumps out in the country, we douse it with diesel instead of gasoline. Diesel will ignite and give you plenty of time to get out of its way, while gasoline will ‘explode’ and singe your arm hair/eyebrows off.

    1. That exact thing happened to my drunk neighbor one night. He went to start a bonfire (a common occurrence at his house) with gasoline, and went back into the house for matches after dousing the pile.
      I felt the shock wave as it rolled through my house, and stepped outside in time to see a burning mushroom cloud rise up 60 or 80 feet into the air.
      My neighbor wasn’t seriously injured, but he did go for a 20 foot ride and landed on his backside. The fire department, which was called because my other neighbors thought it was MY house that had an explosion, instructed the guy about using kerosene instead of gas (burning without a permit is allowed here most of the year, so the guy didn’t get into any legal trouble).

    2. The problem is: it depends.

      Gasoline evaporates. The concentration of gasoline in the fuel-air mixture determines what happens.

      If there is too little gasoline (cold, much wind), you can put out your match in it, just like the video demonstrates with the diesel-like-fuels.

      If there is enough gasoline in the mixture, you get a nice “whoosh”. A burning front that propagates at a speed below the speed of sound.

      If there is EXACTLY the right amount of fuel in the mixture, you get a detonation. The burning front propagates faster than the speed of sound. This gets the loud bang and much damage. If you light your BBQ with gasoline, youl’ll get the “slower than sound” behavior 99/100. But that 100th time you’ll get a big mess….

      1. ” you get a detonation. The burning front propagates faster than the speed of sound.”

        No. You simply just don’t.

        It’s impossible to detonate hydrocarbon fuels in free air by simply burning them, because the flame propagates by pressure waves – which is sound. You need an initial shockwave that is already going faster than sound through the cloud of fuel to make it detonate.

        The flash of combustion that happens at the right A/F mixture is called “deflagration”. It is possible that the flame propagation turns supersonic by confinement in or around obstacles that constrict the flow, but never by simply having the correct amount of fuel to air.

          1. I think they would, because the difference between a deflagrating pile of wood and a detonating pile of wood is whether the splinters fly right _through_ your face.

    1. Correction – my bad – this is about the Fire Point, which is the temperature at which the liquid will continue to burn, rather than the Flash Point which is, like it sounds, a brief flash but not a burn. [JustThink] actually gets a couple of flashes in his video. The Fire point is usually abut 10 degrees higher than the flash point. See

  4. another safety aspect:
    Looks like he is storing the fuel in marmalade glasses. If the upper rim heats up from the propane torch, I would be afraid of the glass cracking. These are not the best containers for experiments!

  5. This post gives me the opportunity to clear up a misunderstanding I once had.
    Higher Octane = more explosive.
    In fact higher octane is less “explosive”, it is less likely to “pre-ignite” in a high compression engine.

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