Jul 23 2012

Firewalk Mishap

According to reports, 21 people had to be treated for burns from walking over hot coals at a Tony Robbins inspirational event.

Robbins is a successful self-help guru with a schtick that depends upon the scientific illiteracy of his audience. After a session of telling people how to “unleash the power within” he demonstrates their new-found power by inviting them to walk barefoot over hot burning coals while thinking about cool moss. This is meant to demonstrate the power of mind over matter. This is, of course, nonsense.

The Hot Coal Deception

Many physicists have used the hot coal demonstration to teach a bit of elementary physics, as there is a very simple explanation for how people can walk over hot coals in their bare feet. I have, in fact, heard three (non-exclusive) explanations. The first, and the one that I think is probably the biggest factor, is that wood coals have a very low thermal capacity and conductivity. This means that they do not hold on to a lot of heat energy, and they conduct that energy very slowly. Therefore little heat is transferred to the soles of the feet – if you walk briskly across them and give little time for heat transfer.

Compare this to other substances with very different thermal properties. Aluminum is interesting because it has a very high thermal conductance (250 W/(m.oC)), but it has a very low thermal capacity. Iron has a thermal conductance of 80, but with a much higher capacity than aluminum. This is why aluminum cookware will cool down very quickly – even moments after you take it out of a hot oven it will be cool enough to touch. An iron pan, however, will take a long time to cool down once it has heated up.

Compare this to the thermal conductance of wood (specifically oak) – 0.07 W/(m.oC). This is tiny. So even though the coals are about 1,500 degrees F, not much of that heat gets transferred to the feet. You would not, of course, want to walk across a slab of iron heated to the same temperature, or even much less. I would rather walk across wood at 1,500 degrees than iron at 200 degrees.

That is enough to explain how a brisk walk across burning wood coals can be safe, but there are two other contributing factors. One is the ash that builds up on top of the burning coals. Ash is a good insulator, and a thin layer of it is enough to slow down heat transfer even further. This could explain why some people at the event were burned and others were not – how disturbed the layer of ash was before an individual walker went across.

A third factor that I’ve heard used to explain the phenomenon (I am not sure how much of a contribution this is) is perspiration on the bottom of the feet, which evaporates and causes a bit of an insulating barrier as well. This seems like the least consistent and important factor of the three.

None of this, of course, has anything to do with the power of the mind. You can think of hot burning lava while walking over the coals, rather than cool moss, and it won’t make a bit of difference. It is the laws of physics that protect your feet, not the ramblings of a self-help guru.

Ramblings of a self-help guru

Speaking of which, what is it, exactly, that Robbins is selling? I think Lisa Simpson summed it up best when she said of a similar character:

“This is madness. He’s just peddling a bunch of easy answers.”

Robbins promises:

Your success coaching plan is your “Pathway to Power.” It is not based on hope. It is not based on theory. It is modeled after those who have already achieved the real results you desire through life success coaching, at the highest and deepest levels.

Life coaching and self-help programs like this are generally not evidence-based in any meaningful way. They are usually just based upon a few simple ideas or catch phrases. They all have a common element, however – spending time thinking about your life, your goals, and how you deal with the people in your life. For anyone who is mostly coasting through life without much introspection, spending a weekend thinking about how to get motivated, achieve one’s goals, and make real changes is one’s life can be a profound experience. That’s the real hook. The details don’t matter.

Wrap that up with some common sense, that “motivational speaker” personality, and a good gimmick and you will probably do well as a self-styled life coach.

Richard Wiseman has done an excellent job of debunking the self-help industry in his book 59 seconds. Most of the advice and “easy answers” that are being peddled is not only improvised, it’s largely wrong. We have decades of psychological studies that actually provide evidence for which strategies are likely to be more successful, and often the real answers are counter-intuitive.

For example, you should not praise a child when they accomplish something. This sounds crazy at first – how can it be wrong to praise a child when they do something good? The problem is praising the result, rather than the effort. This can make children anxious, because they think they will only get praise and acceptance when they do well, something they cannot always control. What they can control is the amount of effort they put into something, so that is what you should praise (even if the result was less then stellar).

What is frustrating is that there is actually a great deal of published evidence that can inform the very questions raised by the self-help industry, but the big sellers in the self-help industry seem to be completely disconnected from that evidence. What they are selling are made-up easy answers, personality, and gimmicks.

It’s all the more annoying when the gimmick is based upon a misunderstanding of basic physics.


18 responses so far

18 thoughts on “Firewalk Mishap”

  1. ConspicuousCarl says:

    It is modeled after those who have
    already achieved the real results you desire

    This claim reminds me of an early reaction I had to seeing the book title “7 Habits of Highly Effective People”. It’s a non-sequitur. What if non-successful people are doing the same things?

    Not that it matters. Most of the content doesn’t sound like anything but obvious concepts phrased in pseudo-profundity (“Begin with the end in mind”… Really? When I start a project, I should know what the goal is? Whoodathunkit. ).

  2. Yeah – I meant to point that out also. He is making a post-hoc fallacy. Unless you do some kind of research that controls for variables, you cannot know what aspects of successful people to model – what actually works and what is incidental.

  3. JamieGeek says:

    The Mythbusters covered the whole walking on Hot Coals thing:

  4. sowellfan says:

    I’m really curious to hear what exactly went wrong with this round of firewalking. From other comments on articles about this, it seems that it’s not terribly uncommon for people to come away with minor burns and blisters – but it sounds like more significant injuries happened this time. Perhaps they used a different fuel to make the coals? Maybe if they tried to process more people across the firewalking pit, the ash layer got removed by successive walkers, and didn’t have time to build back up?

  5. Joctrel says:

    My speculation, based on watching that Mythbusters episode, is twofold:

    1) You’re gonna get minor burns either way, but how bad they feel depends on your pain threshold, which is subjective. A third degree burn, essentially equivalent to a sunburn, is not a big deal on the thick skin of the soles of the feet. Mind over matter comes into play because it is possible for some people to ignore the pain of a sunburn. The blisters described might have been indicators of higher-degree burns, which would have been caused by some other aspect of the trick going wrong.

    2) A major factor to the trick is to walk at the right speed. That’s why they call it mind over matter. It takes some amount of concentration to maintain a pace that’s not too slow and not too fast. Running seems to make it worse, perhaps because of the higher g-forces pressing your feet down into hotter regions of the coals. On the other hand, and a less common problem for flammable human beings full of nerve endings, if you walk too slow, you get cooked of course. It doesn’t appear to require superhuman concentration to achieve the optimal speed, since the parameters aren’t extremely tight. But it does require some self control. Mostly to suppress the flight instinct.

    While it may come out later that there was some changed parameter, maybe a starter fuel was used, or something else made the coals hotter or more conductive. My speculation is that the trick was performed normally, but the participants weren’t sufficiently prepared and informed. Maybe it would ruin the atmosphere, but the simplest thing I can think of to say would be “you’re going to have a very strong urge to walk faster, but don’t do that, because it will make the burns worse”.

  6. SARA says:

    I’ve noticed that there is something profoundly uplifting in being with a group of like minded people and actually DOING something as a group. Particularly if the action is thought to be “greater than normal” behavior. That is why church services, weekend seminars, etc can be inspirational. Actually it doesn’t have to be inspirational. It can be going to a football game or attending a fun convention. It’s a group of people with a focus on the same thing.

    I have no idea what the phenomena is, I’m sure it’s centered around our naturally social nature.

    Walking over coals is definitely the gimmick, but I think the thing that makes people do it is that uplifting sense of being part of something, being greater than just yourself. As good as Robbins is at manipulating people, I doubt he could do it without having a group feeling solidly established in his audience. I bet he doesn’t do it at the beginning of the seminar. I bet it’s at the end.

    I”m not probably not explaining this clearly but if anyone knows what that phenomena is called (besides a mob), please let me know. Anyway, it really bothers me when people leverage it to manipulate people.

  7. phidauex says:

    Joctrel – a Third Degree burn is a highly severe burn – it means that there has been significant tissue and nerve damage. Second degree implies tissue damage to the first and second layer of skin. First degree is like most sunburns – first layer of skin damage only. Third always requires medical attention. 2nd may require it in some cases, and first rarely does, beyond basic first aid. If people were getting third degree burns, that is a big deal.

    I’ve been a professional fire performer, and have done fire walking in this manner, as well as fire eating, fire contact, fire breathing, and other such activities. I also have a background in physics and science education, which comes in handy for those sorts of pursuits.

    Fire walking’s safety lies mostly in the heat capacity and thermal conductivity of not just wood or ash, but in the structured carbon matrix left behind by the burning wood. This material is a lot like aerogel in structure – lots of air content, and highly insulating. It’s low thermal capacity and conductivity means that it can be very hot, and still transfer energy very slowly.

    The key is in the preparation of the coals – as the wood is burned down, typically pine for it’s quick burning and stable coal shape, it is continually raked out and moved around, breaking the coals down into relatively small chunks with high surface area, which burn quickly. Once the wood is broken down into homogeneous coals of roughly similar size, they are spread into a layer, and somewhat compacted with a shovel or rake. This reduces the surface area exposed to air, slowing the rate of combustion significantly. The very top surface, exposed to air, continues to burn faster, while the inner sections slow combustion considerably (but remain hot due to their insulation). During this time the instructor is getting everyone prepared, and the very top layer of coals is burning out, consuming the last of it’s fuel. By the time you actually walk, the very top layer is burned out carbon matrix with hot coals below.

    You do need to walk at a consistent pace, heel to toe, with very dry feet. Burns occur when part of your foot goes down under the top layer of coals (as can happen if you walk toe to heel, or if you try to run, digging your toes down into the coals), or when coals stick to your feet (if your feet are wet). The carbon is insulating, but you are still relying on the very high heat capacity of water in your feet (not ON your feet, but in them) which would take close to a full second to heat up enough to burn you at the heat transfer rate of the carbon.

    Done properly, you receive no burns at all, not even minor or 1st degree burns. You brush a little dust off the bottom of your feet, and smile. Minor burns are not entirely uncommon, since the process is still pretty delicate, and hey, it is still fire. There is no mind over matter component, and it isn’t magic – just a little physics, and a lot of self control.

    I think their biggest problem is the number of people they were doing at once. 6000??? The experience is best done with a small group, because you need to really trust the people you are with, because that trust is what causes the self control. The way I’ve done it, the instructor has everyone pair off, and one person stands at the far end of the firewalk, with a look of confidence and trust. The “walker” walks along the coals toward their partner, not focusing on the coals, but on their partner’s eyes, sharing their confidence. Focusing straight ahead keeps you moving consistently, and prevents you from reacting like you “should” react to being on top of a fire. The experience works well for a small group, where everyone can watch everyone else go, and you develop a relationship with your partner as you provide an anchor for each other.

    The experience does tend to be quite powerful for people, but not in the cheesy mind-over-matter magic that the self help “gurus” seem to be so fond of. Why dress it up in fancy language and claim you invented a system? For generations people have known that shared challenge brings people together, and that achieving something that you thought you would be too afraid to do builds confidence and trust. No woo necessary. When you do something you thought you couldn’t, and did it because you trusted your companions and yourself, that is a good thing to experience.

  8. andrewslaughter says:

    The funny thing that I noticed is that the guys wheeling the hot coals out had gloves on! If the mind over body really works you would think the help would not require gloves and just say “cool moss”. They had a typical believer on Foxnews this morning, a video worth watching. But like Steve Salerno has said, Tony Robbins and the rest of the movement provides no real benefit or any tactical tools that they can take away.

    I’m sure Tony Robbins will say something like “the 21 participants didn’t say cool moss enough” or some other mystical hand waving nonsense to deflect any criticism of his circus act away.

  9. DOYLE says:

    If you want to measure the efficacy of any motivational speaker,guru,messiah or visionary,simply inventory the product stream that follows.And just like any cash cow,notice the sequels,revisions and hybrid products that keep coming in as new and improved.Motivational shit 2.0

  10. Fourier says:

    I have quite a bit of knowledge of Robbins’ material (attended two live events, crewed in two). I went in as a scientist, though without much understanding of psychology. I realised that most of it was superficial at best, false at worst (and the annoying woo element really irritated me) but I still got a lot out of it. It was an interesting process learning about the real science (or not) behind his claims over the subsequent years and I’ve discarded most of the beliefs I picked up from those events since then.

    However, the fire walk has stuck with me. Even the first time I did it I knew the science behind it and I didn’t buy any of the woo stuff – but that doesn’t mean it’s not a good exercise. Even though I knew all the science, it’s still difficult to step out onto burning red coals barefoot. It was a good exercise in training myself to trust in science and not intuition. I suspect I wasn’t the only person in the room who interpreted it that way. I’ve applied that mindset later on in life to getting over fears (“Ignore your emotions – the science knows best”).

  11. eean says:

    @phidauex “why the woo?” is often what I think regarding these sorts of stories. Or like acupuncture – it could be just a weird form of massage but they have to make it about chakras.

  12. beddoe says:

    What I find the most facinating thing of all is that after the first 5 or 6 people got burnt – maybe just maybe, the others might have thought “Hang on this may just be a bad idea”

    By the time you have 20 people rolling around holding their smoking, blackened and blistered feet you have to ask why person number 21 thought it was still a good idea!!

    Maybe they felt left out and thought “I’ve paid all this money to Tony Robbins – I’m going to get something out of this – even if it is burnt feet”

  13. BillyJoe7 says:


    I’m pretty sure Joctrel just made a typo.
    He clearly meant to say 1st degree burn, not 3rd degree burn.

    But I see you disagree with Steven Novella about the moisture on the feet.
    Steven: “perspiration on the bottom of the feet…evaporates and causes a bit of an insulating barrier”
    phidauer: “Burns occur..when coals stick to your feet (if your feet are wet)”

  14. As I said – I heard a physicist give that as the explanation, but did not find it very compelling myself. The coals sticking to moist feet point seems plausible also.

    I think the low thermal conductance and the insulating ash are the real major factors here.

  15. BillyJoe7 says:

    I don’t suppose anyone has conducted a test of dry vs moist vs wet feet?

  16. etatro says:

    Billy – Have you ever pulled something hot out of the oven using oven mitts that had gotten wet? It burns. You want dry feet like you want dry oven mitts.

  17. BillyJoe7 says:


    No, I’ve never done that. Have you?
    Is it better to walk barefoot over hot coals or wear a pair of wet socks while doing so? I dont know. I’ve never tried it nor have I heard of anyone else who has done the comparison.

  18. Tom Nielsen says:

    Just a small correction. It seems that you either made a typo, or read from the wrong row in the table you linked to.

    You wrote the thermal conductivity of “wood, oak” to be 0.07. The table says 0.17.

    0.07 is the thermal conductivity of “wool, felt”.

    Still a tiny value though.

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