My studio now smells like burned post-it notes. If you're interested in the live Q&As consider becoming a supporter on Patreon (I'll see you on the Discord!): stvmld.com/ndg9-y-x You can also discuss this video on REDDIT: stvmld.com/awh34y3s The sponsor is KiwiCo. Get 30% off your first month of any box: kiwico.com/stevemould
Early hot air balloonists thought it was the smoke that gave them lift. All demonstrations of the effect were done over fires. In the home, with a paper bag held into the smoke, it would rise & hit the ceiling. Letting the smoke out in an obvious fashion the bag would fall. So the Montgolfiers flew using the smokiest of fires made from straw, humidified wool & even old shoes! The denser the smoke the better! It wasn't until later that people realised it was hot air, not smoke, that gave you lift!
@@SteveMould the algorithm suggested (regularly) a good video, it knew exactly what I wanted to watch & like - How? Spoiler - because I've already watched both suggestions, liked both, & had the algorithm suggest them multiple times.
Incense “smoke” is not just suspended ash from combustion. Incense contains a lot of oils and the combustion is incomplete. Note the brown droplets of oil on the glass from the cross section. The smoke is so much heavier out the bottom because it’s mostly uncombusted oil in suspension. If you were to trap and analyze the smoke from above vs below, you’d find a very different oil content ratio.
@@Manoplian Paper is not just wood pulp, there’s a binder component which is combustible and liquifies before burning. “Heavy smoke” in general is a suspension of unburned fuel. You can light it and it will readily burn in most cases.
You are to things what Tom Scott is to places. You find things, explain what makes them interesting, then explain how they work, Tom goes to places, explains why they are interesting and how they work.
Well said! I'm always ready for them, they're so consistently good that even if they title a video "Reading the Terms of Service" I'd be SO READY AND EXCITED!!!
I’m in the fire service and we do a lot of fire science and learning about fire phenomena. The first thing we learn is all about pyrolysis. It’s a really interesting subject. For example, when any material reaches a certain temperature, it breaks the material down and the chemicals are released into the atmosphere which is, like you said, the flame part. Once this is gone you are essentially left with coal (assuming it’s wood that’s burning) and that will just glow because the gasses are burnt off. We sometimes come out of training runs and our fire kit is pyrolising. Within our initial course the light a fire with lots of timber sheets, they lay out a small section of carpet about 3 meters away and have 2 cups, one empty and one half full of water. Empty cup melts and half full one melts down to the waterlevel (this is to show how much water can absorb the heat) the carpet starts to release nasty looking gasses whilst curling up around the edges, after a while this carpet just bursts into flames even though there is a few meters separation. A good demonstration is to heat up small bits off wood within a glass jar above a Bunsen burner (attach a tube to jar to allow the steam and gasses to exit away from the flame) at first you will get water droplets and then the smoke will come out white where it has a slight moisture content, this will then turn brown/green and this will be the flammable gasses. Once the process is over, the original wooden pieces are now just bits of coal ready for the BBQ. This would be a really cool video and you can then demonstrate flashovers and backdraughts.
So, pardon me if this is a silly question, but is this coal, like, actual coal? I’d love to know how wood can turn into that. Or is it more briquettes that you’re making? I also definitely agree about backdrafts. Probably the only thing Hollywood gets wrong because it’s more spectacular in real life, not less.
@@uzaiyaro sorry, this is to make charcoal. The briquette are, I assume, made in a similar way but with a manufactured wood beforehand. Like moulded sawdust? I’m only assuming on how they made.
I used to do nosework with my dogs, which is a sport where the dog is supposed to pinpoint the source of a specific smell. When you get into that, you learn all kinds of surprising things about how and where air travels within a room (since it affects how the smell travels and how/whether the dog can interpret it). In some of the seminars, we used "smoke pencils" or "smoke pens" to explore what airflow does next to doors, in sunny spots, next to corners, etc. That's what these smoke experiments reminded me of.
About the Mexican wave, or as we call it in the US simply the wave, I've seen a situation where there were two waves in the audience moving towards each other. I was genuinely tickled to see that the waves canceled each other out when they met.
@@DampActionRC I'm sorry, I replied to the wrong comment (I intended to reply to an irrelevant comment in this same video). I hope you accept my apologies. This effect you're talking about seems pretty cool. Maybe somebody caught it on camera so we could all see?
This channel is freaking amazing. I love that it's never "and that's just how it works" - there's always "but there's something that didn't make sense..." followed by more digging. This is an approach and attitude that we need more of in society - never assuming that we know everything there is to know about a subject, being aware that there is always something more going on that we haven't figured out yet.
The misnomer Mexican Wave amuses me. It was invented in America, and from here reached our neighbor Mexico where it was seen on global television at the World Cup, so the rest of the world associated it with Mexico. In America, we just call it "the wave." I don't know what they call it in Mexico.
I have been thinking about this topic recently so thank you for this video - I'm a blacksmith and when I fire up my forge, often times smoke from the coals will cling to the horizontal forge table before very slowly starting to rise (or settling I guess). I figured it was due to the steel table cooling the smoke before it had a chance to rise. It looks quite surreal. This video makes me think that my case, the convection probably doesn't get to pull all the smoke up with it; as the smoke is forced out of the coal mound to all sides, it ends up too far away from the convection stream to get pulled up, and it gets cooled by the table and simply lingers for minutes.
My own hypothesis is that it works similar to underwater brine pools. Some conditions allow the smoke containing air to get unusually super saturated and so denser, but also somewhat stable so once it meets normal air with its normal concentrations the two gas masses don't mix as easily/fast as they otherwise would.
My friend was showing me one of these a few weeks ago, and it absolutely blew my mind + had me completely stumped as to how it works. I'm so grateful for this explanation 😬
This was very interesting! I especially liked the comparison with crowds exhibiting fluid like behaviour. This made me think of the terrifying scenario of crowd surges that often cause hell incarnate (eg crush injuries in festivals or a nightclub) but can be modelled fairly accurately with fluid dynamics. I didn’t expect to think about that so thank you for another great video!
Is there an upper limit on the size of smoke fall devices? It'll work on incense cones or rolled post-it notes, but what about something like a log with a hollowed core?
hawk 7886, I've seen it happening with small logs too that had a hole or a crack. don't know about bigger ones, I just don't have enough experience with it
Your comment reminded me of this experience I had: I remember where I almost saw this phenomenon: it happened whilst I was burning a heap of bamboo stalks! I simply chucked them in a fire, only to be spooked soon thereafter by literal wooden bombs as the pressure inside the sealed cavities made the stalks burst vigorously. So, for the next batch, I poked holes throughout the pieces which had sealed cavities, basically creating a long tube of very oily wood. While burning, which wasn't easy at all, lots of dense white smoke oozed lazily out of the top, barely rising; I'm sure that, had I lifted the cane out of the fire, I'd have witnessed a smokefall out of its bottom!
Something i remember as a child is smoke from the chimney falling when there was a snow storm on the way. It was explained to me that the high pressure front of the storm forced the smoke down low.
@@purplezart that would actually explain better the phenomenon, less pressure equals less air thus the capacity of it to suspend any particles would be diminished
So im assuming its more like when a fire is just being lit or is small? but when its significantly colder outside and the flue/ chimney is cold once a fire is lit it can create a backdraft causing the cold air to sink in to the chimney, partly the reason for they flue so you can close it when not in use and if you ever noticed on cold days there can be a significant flow of cold air from a chimney if you don't have that shut. Will also cause the smoke when lighting up a fire to just gointo the room instead of out the chimney until it gets warm enough and enough upward heat and airflow to create a flow up and out. Its called the stack effect just as an FYI but as a side note something that's not commonly known is that when there are large atmosphereic pressure changes like storms it can also cause a net flow in or out of cave systems or underground tunnels.
@@connorjohnson4402 absolutely this. It’s about fighting the cold dense air sitting on top of the chimney, like the upside down version of putting your finger on the end of a straw and into water. We would have issues starting our fireplace if it was below 10°F outside. It would take quite a while for the heat (and annoyingly smoke) to find their way up and out.
The post-it note example reminded me of years ago when I was a smoker. Break the butt off of an unburnt cigarette. Pull the cotton out of the paper of the butt. Then take the cellophane that's around the bottom of the cardboard box they come in. Turn the square shaped cellophane upside down and set it on a flat surface. Twist the butt paper into a thin paper tube. Light one end of that paper tube. Use the lit paper to burn a tiny hole in the top of the short side of the cellophane. Then turn the burning paper tube around and stick the unlit end into the hole you just made and let it burn. The smoke will flow from the paper tube to the inside of the cellophane and fall downwards just like the post-it. I have a theory that maybe Steve knows about the cigarette trick and came up with the post-it trick because he didn't want to make cigarettes look cool which is a great thing. Don't smoke, kids.
As people say smoking is harmful to you and people around you too. Breathing in smoke but not smoking yourself is know as secondhand/passive smoking. You can still get all the horrible diseases from regular smoking as well as secondhand/passive smoking.
I came to see if anyone knew about this besides me, but I can go one step further, if you'll leave the cellophane on the pack you can pull up down to increase the flow rate.
I absolutely love how along the way of learning about this cool new trinket I now want, I also learned two very cool things about smoke and burning, how the way we conceptualize them is only due to circumstance. Amazing insights! I love thinking about things in completely new ways and you do a fantastic job at bringing that out!
This is exactly what I was looking for. I want to make Backflow cones out of my regular cones and didn't know how far to drill the hole thank you for this video!
That's awesome! We always had neat incense burners at the local flea market, but I've never seen one that had a smoke waterfall! It's usually Grim Reapers and Dragons with smoking mouths and eye holes.
I've been using nag champa for years and I've recently purchased a few Japanese ones. They're so much better! My favourite so far is autumn leaves and I giggled when you mentioned it! The only downside with these is that you need to constantly replace them and have many unlit just there in the open air. Very subtle compared to harsh bamboo smoke. It doesn't stick on walls etc. But it's a good reminder that the scents are from wood and are not highly perfumed. Great video!
This was described to me by a science teacher as creating a small vacuum or low pressure zone, where air is moving up but the smoke gets thick enough in the zone and so heavy enough to fall.
We have one of these and, today, I discovered something else weird about these incense cones. Try placing one on a flat-based candle holder (as used for ball candles, for example). When I did this today, I discovered that the smoke simply pools at the base of the cone. I've also noticed something about the smoke generated by these cones that may play into the physics - it seems to be much more oily than you'd expect (judging by the residues on our 'waterfall' burner) - which may play into the speed at which it cools down, as well as providing a greater density when suspended. Fascinating stuff - good work.
Thanks for yet another great video! Maybe an idea for a future video: I have been wondering how blades cut on the molecular level. I.e. a very sharp blade does not need much force at all to separate a material, is there any particular molecular/atomic level interaction between the blade and the material being cut? Does the blade just wedge itself in between the target material atoms mechanically pushing them apart, or is there more to it than that?
I really appreciated that, "a lot of smoke is coming out of the top; it's just moving faster, because of convection, so it's harder to see." was reiterated into "for a fixed smoke flux a stream of smoke moving faster must be less dense."
I've never seen the excitability of bubbles quite so clearly, but I DO love watching the activation of those sodium acetate heat packs, and now I know what to call them!
Interesting fire moment I had recently: I had an overgrown ditch (steep grade) connected to a lawn that gets mowed. There was a mat of dried grass across the face of the ditch, and when I lit the righthand edge, the fire slowly crept across sideways, like a giant incense stick, until it reached the left hand edge, but the fire never moved into the mowed lawn, because there was no fuel, no mat of dried grass. Reminded me of the Forest Service’s clearcut lines that act as firebreaks, helping prevent widespread forest fires.
I once saw this effect with a lollipop stick, or possibly a q-tip that had had the cotton pulled off, when I was a kid. I have no idea anymore why it was set on fire, but because the paper was rolled so tightly into a solid tube, the inner hole was very narrow and the smoke came out the other end in a jet rather than falling out like a liquid. It was cool enough for me to remember it even now. Unfortunately, they don't seem to make those out of paper anymore, it's all plastic, so even though I've thought about recreating it several times, I've never been able to. Although it's not like I am constantly buying lollipops to see what their sticks are made out of, so maybe they are still around somewhere.
Expanding on your notes around 7:15: Smoke is flammable, for the reasons which you gave here. If one were to collect a bunch of smoke and introduce a flame to it (in a mixture of oxygen), then the smoke would ignite. That is why smoldering fires produce a lot of smoke but firey fires do not, I think.
He literally gave reasons why the incense smoke is not (so easily) flammable. You seem to be talking about other kinds of smoke (smoke from recently extinguished candle) and thinking it applies to all smoke, and not listening to what Steve is saying really.
Here's another question for you: what causes the regular "puff-puff-puff" pattern of smoke coming out at 5:20? Cool video! I've been wanting one of these things for a while, haha.
7:40 Don't say it Don't say it Don't say it Don't say it Don't say it Don't say it Don't say it Don't say it Don't say it Don't say it Don't say it Don't say it!
5:51 this I used to do in front of the fireplace as a child. I discovered when I rolled up pages of newspaper, the smoke would flow out the other end when I put the tip into the fire in the fireplace. The smoke would then flow around until enough would accumulate and reach the flames where the gas would ignite causing the flame to travel to the opposite end of the newspaper tube.
Fluid Dynamics always freaks me out. It is easily one of the most complicated fields of mechanics; even the _simplified models_ are hard to work with a lot of the time, and involve a lot of Navier-Stokes equations and things like that.
Weird, I just randomly came across these incense burners on Amazon the other day. I think it was the first time I’ve ever seen them, that I can remember anyways. I just assumed the ceramic burner had to be placed in the freezer prior to burning in order to cool the smoke to the point it would descend down instead of rise
I learned how to make a smoke fall by rolling up the paper and tin foil from the inside of a cigarette pack then slipping the cellophane up on the pack so that the pack is only half in it cellophane burning a tiny hole in the cellophane and placing the role of tin foil and paper in the hole and lighting it... I learned this trick in the 80s... This is the first I've seen anybody try to give any kind of scientific breakdown of it. Awesome job, thanx. Also I didn't know they made incent burners that use that and I burn a lot of incense... this is an amazing find to me.
Weird thing is... I feel like this entire episode is a promotional commercial on Back-flow incense burners. lol I've never heard of these until now and now I want one!!!
Great video! As always (in my extremely biased opinion), the more fluid dynamics videos the better. This whole exercise feels exactly like the kind of thing we'd get as a homework question for my Convection class during grad school fluid dynamics... so much so that I am really tempted to dig out my notes and textbook from that class, which is an expert example of nerd-sniping, so well done I guess. Anyways, I definitely agree that entrainment is the core reason why it "sometimes falls and sometimes doesn't fall". The combustion is heating the air around it, setting up a free convection flow due to the density differences, which then entrains air around it to flow too due to shear setup by viscosity. The area of effect around the plume of this entrainment acts in some ways similar to a boundary layer, at least insofar as the effect obviously diminishes with increased distance, though I can't remember what shape that "boundary layer like" entrainment takes, or if it follows the same sort of parabolic or log-law behavior as a normal boundary layer. (To get the plume shape I think you need to know both the momentum and thermal boundary layers and I think I remember that if you use a boussinesq approximation to simplify N-S you can analytically derive the thermal boundary layer profile, and that it is steeper than the momentum boundary layer). Anyways, get the tracer (i.e. smoke particles) far enough away and they won't be entrained. Or you can just block the flow communication entirely with a giant acrylic enclosure, which works too. I am sure there are dozens of fascinating CFD and flow visualization papers out there on this topic which can show in beautiful detail exactly what is happening (partly because buoyancy driven flows and free convection are fundamentally important in tons of applications, but mostly because buoyancy driven flows almost universally make stunningly gorgeous CFD or flow-vis videos).
A curious note on this... if you make a cylindrical wick (i.e. stick a piece of paper as a hollow cylinder in some wax) the smoke will get caught in the centre... to the point about the smoke fall in a stickey note working I wonder if its a matter of the heavy particles having somewhere too fall before they are caught by those fast moving convective currents...
I remember learning to make a smoke waterfall with..... Smokable products.... just by pooling the smoke in my mouth and pushing it out slowly. it always blew my mind. Thanks for showing me how it works!
@@tatertott2390 sure but I mean actual torches lit with fire. Is it possible to engineer a torch “handle” so that the smokes goes down like this… that’s what I mean. Bc you know how torches leave black marks on walls and ceilings.
When I was a kid we'd make them all the time with cigarette packets. If you set a pack of smokes, lid down, and lift the bottom part of the plastic wrapping to create a square see through cellophane housing. Then we'd roll a piece of paper just like you did, use the burning tip to poke through the cellophane, leave it in, and watch the smoke fall.
@@jasperwong2970 many of the smoke particles as they contain oil would stick to the bottom of the glass. And the finer ones would probably stick on top. So I'm guessing most of it would remain on the bottom. Interesting experiment to try though
I remember where I almost saw this phenomenon: it happened whilst I was burning a heap of bamboo stalks! I simply chucked them in a fire, only to be spooked soon thereafter by literal wooden bombs as the pressure inside the sealed cavities made the stalks burst vigorously. So, for the next batch, I poked holes throughout the pieces which had sealed cavities, basically creating a long tube of very oily wood. While burning, which wasn't easy at all, lots of dense white smoke oozed lazily out of the top, barely rising; I'm sure that, had I lifted the cane out of the fire, I'd have witnessed a smokefall out of its bottom!
I had wondered how these work for a while. I had assumed they had to be cooled down in a refridgerator or they had an ice cube inside. Thanks for the explanation.
I'm glad you mentioned that KiwiCo doesn't just do subscriptions. I've considered getting something like this as a gift for my nieces/nephews, but the subscription bit always turned me off. I'm sure the subscription is great, but I imagine after a while boxes of these stack up and become clutter. A one-off box seems like a nice way to give them (and their parents) a taste of what KiwiCo has to offer, before committing to a monthly subscription.
I love how Steve went out of his way to describe the Post-it note - the same size and shape of a cigarette, with smoke at one end and a flame at the other - as just a rolled up Post-it note with the diameter of a pencil.
Pretty sure my videos prompted the invention of these things. I did a few videos on early TH-cam about making smoke waterfalls with rolled sticky notes and these popped up a short time later. People used to do a similar thing as a cigarette trick but I think it was forgotten for a time between the 90's and early youtube.
@@ajazman7 If you know of these devices existing prior to 2013 tell me what to Google so I can learn about them. Far as I know that's the first time the sticky note trick took off on the internet, then a few years later I did a follow up video, followed by a channel called Giaco Whatever trying it with incense, and about a year after that they showed up on store shelves.
@@Nighthawkinlight The earliest patent of this thing I could find was CN201230066466.3 Patented 2012-03-20, Which the guy claimed he discovered it back in 2010. But I'm pretty sure I've seen something like this back in 2008 or 2009 at some random antique(and fakes) market in Luoyang, Henan. It's nice that you found this behaviour and posted a video about it, but there's only so much things to be found out by billions of human on earth. Claiming something to be your invention is a bold move and I respect that, cuz I've done things like this before and I still cringe till this day whenever I think about it.
@@solivictus Nice find! Beat my video by a year then. Note I did not claim I invented these, I claimed to have probably inspired their invention. Proved me wrong there. At least I still have claim for inspiring the Eggzer/Golden Goose.
@@Nighthawkinlight I too once thought others' creation was inspired by my finding, and turns out they figured that out by themselves, and I wasn't even the first one who discovered the mechanic. There's just too many human on earth thinking at all times 🤣. Hard to say who inspired who or who came up with it first.
Thank you for pointing out the pomegranate juice... I was watching it thinking it was a complex chemical reaction in lab glassware, as soon as you mentioned it I could see the Pom bottle.
Smoke gases are mainly H2O ( lighter than air), and CO2 (heavier), The visible parts are droplets and solid matter (heavier). Smoke cones evaporate a lot of oil, so the mix is potentially quite heavy.
@@nerfherder4284 it's quite easy to estimate density of gases, it's proportional to their molecular mass. so, for water it's 18, for CO2 it's 44. average molecular mass of everything that air consists of, is about 29. therefore, water in gas form is lighter than air while CO2 is heavier. CO (28) has almost the same density as air
@@nerfherder4284 I know it's counter intuitive, but gas densities are proportional to molecular weight (each molecule claims the same amount of space in an ideal gas). O2 and N2 are 32 and 28 respectively . H2O, being an oxygen with two very light H, is 18. CO2 is 46. The whole thing is valid for H2O as a true gas; as soon as it condenses things change, obviously. Condensing water makes white smoke. I suspect the bluish smoke of incense is mostly essential oils. Air can carry quite a bit of water in mixture before it starts to condense out. As a sailplane pilot you know everything about water being light; it's the main driver of stable thermals.
2:40 I was guessing that the vaguely conical shape of the hole acts like a nozzle to some extent? Pushing the expanding gas down, creating a draft with it that pulls most of the inside smoke with it ; the smoke you see emanating from the top is the part coming from the outside of the incense cone (perhaps)?
Wait, but when you light incense there is a flame and you have to actively blow it out… so what sets apart a situation where a material can both burn and smolder? Is it that the open flame of a lighter is hot enough to vaporize enough fuel in the medium to sustain an open flame? Then when you blow it out, it continues to smolder because the reaction of burning isn’t hot enough to vaporize the oils for a sustained open flame? Would some materials just contain certain oils with flash points very close to that of an open flame vs a smoldering reaction?
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Several things I hadn't considered before. Thanks very much. I'd imagine that the smoke falls because its not being caught up in the draft flow to the flames, partly because there aren't any flames, and partly because the smoke is released far enough from the combustion. As always, interesting stuff, told clearly, concisely, and with a sense of humor and wonder. I'll be back. 🙂
Thanks for the video - but Michael Faraday covered much of this - brilliantly - in his Ri Xmas Lectures on the Chemical History of the candle in 1848 (yes - nearly 175 years ago). His book on the lectures is in the public domain, and various people have tried to recreate his demonstrations on video (some are quite tricky to set up).
@@agimasoschandir It’s sad that many people are unaware of Michael Faraday - and particularly the Christmas Lectures for young people that he established in 1825 whilst he was director of the Royal Institution. He is one of my science heroes. This year marks the 200th anniversary of his invention/discovery of the electric motor. The Xmas lecture series is still going strong, and they have been broadcast on television since 1936 - so are probably the earliest (and longest running) science programmes on television. Various people have repeated his lectures and demonstrations (some are quite tricky to set up, and others would be considered downright dangerous today). A quick search on your favourite search engine will reveal videos of them - and the Ri’s own channel has videos of many of the televised lectures (well worth exploring).
Fill a medium to large glass up with warm soapy water and shake it around while your hand covers the lid with a seal. You will find a significant amount of air pressure whooshing out when you remove your hand. Do the same thing without the soap and you will find that there is not any significant air pressure created. It seems to me that bubbles are able to create pressure through tensile forces in a way that I don't think has been fully detailed by physicists. I think this could have implications on the scale of the cosmos. I know this sounds asinine, but I hope you will humor me if you are running out of ideas for more videos.
I experience this effect when making smoothies in a blender. I like them without soap so it is probably just the temperature difference between the cup and the ingredients which leads to the air changing their temperature from the cup's temperature to the ingredients' temperature.
Great video as always, btw I think the convection still happens inside the tube but its forced to compress and go out, cooling along the way and getting dense .
I used to create smokefall's all the time when I was younger and smoked cigarettes' about 10 years ago. I'd take a small, long, piece of a discarded cigarette box and roll it up really tight into a small paper tube, leaving just a small hole thru the roll. Then, I'd light one end on fire and blow it out to form a small tinder. Using that lit end, I'd make a small hole into the center-bottom cellophane wrapper still attached to the discarded pack of cigarettes, inserting the un-lit end of the paper tube into the small hole and upright. I'd then turn the whole assembly with the bottom of the box facing upwards, and slowly raise the delicate cellophane wrapper as it held the previously created paper tube, then stop just before it came off the box and watch as the smokefall hit the box and collected and the bottom of the pack of cigarettes. They were always fun to watch and interact with.
With that hole in the middle, I'm thinking of solid fuel boosters that burn from the inside out, spewing hot matter below them. Would it work even better if the incense was burned from the bottom/middle?
We used to demonstrate Brownian motion using smoke from a burning paper straw. You hold the straw at an angle to the horizontal and light the high end. As it burns the (waxed paper) smoke falls down the straw because it's actually heavier than air and being at the bottom of the flame inside the tube, no convection currents exist top push it upward. (The smoke was collected in a dish under a microscope and viewed to see the motion). A candle shows the same behaviour if you blow it out and it continues to smoke. As the wick cools and the convection currents stop, the heavy smoke starts to fall down the candle.
If you want to get into exploring convection currents, you might try setting up something for Schlieren photography/videography. Tons of fun and an excuse to purchase an expensive mirror!
My favorite way to do a burner is a mason jar. Large volume mason jar with a few holes poked in the lid allows you to observe the unperturbed flow from those cones. You need multiple holes in the lid to allow enough air to get a good flow
Hey Steve, I have seen smoke from chimneys go down, instead of rising. only on certain days, I think those days are generally very cold (below -20C) and calm, no wind. It's odd when it happens, and I have never been able to explain it. I suppose the cooling of the smoke going up the chimney would account for the falling smoke? Really interesting video, thank you
I have one of these incense burners and it's really soothing to just watch with some soft music on, when I've had a stressful day. I've always wondered what causes it to work.
So, I think part of the way this works in the post-it note, is that the hot gasses expand, right? So this creates a pressure through the tube, so long as the pressure in that tube (through being long enough compared to thin enough) is greater than that of 1 atm, there will develop a draft through the tube, and a pressure gradient with the highest pressure side being the end with the combustion, this ensures that the flow continues to drift through the post-it note from top to bottom. On the top side, any gasses that are made that are not into the tube obviously dissipate freely into the surrounding air, and so the draft follows normal convection expectations. You should be able to test this sort of thing with a water, a heater, and a tube. Heat the water at one end of the pipe and then you can use drops of dye to see where the water is moving from convective currents. I suspected, if the heater is in the pipe, while some dye will come back out the end, a flow should build pulling the water down. One would probably have to play with the parameters though: width of pipe, length of pipe, temp of heating, etc. Since not all parameters could generate a pressure greater than the end side of the pipe. (Perhaps this should also be noted it should flow more if the pipe is straight level, rather than deeper.)
My guess is heating water will only cause upwards draft through the tube... Thermal expansion of water is somewhat tiny. The downwards flow through the post-it is dependent on the fact that gas expands a lot, and additional gas is created due to paper burning.
Have you ever investigated adhesion in smoke? I know most basic cotton clothing seems to display an interesting "Stickiness" as smoke passes over it. Now I'm wondering how other materials display this...
Years back I picked up a wine bottle that was modified to be an incense burner by having a couple holes drilled in the bottom. An incense stick would be suspended in the neck of the bottle by a key ring, and the smoke would drift out the holes at the bottom. Unfortunately, the oils would also thoroughly stain the surface it was on.
6:24 but what if that bent copper pipe is a much more effective heat sink than that metal lid you were holding before? You ruled out the heat sink effect of that lid, but the copper pipe may be effective enough that you mush consider hear sink properties a factor again.
It is like folk do not observe what they see, I for an example have seen smoke low to the ground rather often and even in the photoage at 1:54 you can see smoke falling down the hill so the trees below are covered up to the tips. So for me smoke just follow the air, so where the flame is located it goes up, but if the smoke come to coulder air it will think to the bottom, so in a room with a good average temperature that have same temperature at the top and bottom the smoke would spread evenly. And air work a bit like water, if you have a container with room temperature air you can then pout could ait into it, it will follow the same path water would take and start to fill up from the bottom. Like if you do not have a container you have all the turbulent air around you, the more turbulent the air is the less chance there is that it will go straight down, it will thin out much faster, a bit like a smoker exhaling smoke, so when you place that thing on top of a container there is no turbulent air, that thing is so porous that the flame suck oxygen through it rather from the jar under, so the smoke come out from the underside is just coulder and sink to the bottom where it is then wanted out on the bottom, like a house on fire until you open some holes at the top above the fire. Or have I missed something, I am not very well educated so I may be totally wrong, If I am, pleas educate rather than make a angry comment.
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Maybe you could burn some incense to mask the smell?
Early hot air balloonists thought it was the smoke that gave them lift. All demonstrations of the effect were done over fires.
In the home, with a paper bag held into the smoke, it would rise & hit the ceiling. Letting the smoke out in an obvious fashion the bag would fall.
So the Montgolfiers flew using the smokiest of fires made from straw, humidified wool & even old shoes!
The denser the smoke the better!
It wasn't until later that people realised it was hot air, not smoke, that gave you lift!
@@Aengus42 interesting!
@@SteveMould the algorithm suggested (regularly) a good video, it knew exactly what I wanted to watch & like - How?
Spoiler - because I've already watched both suggestions, liked both, & had the algorithm suggest them multiple times.
If you make a drinking straw sized tube of paper and hold it at an angle, and then light the top end. The smoke wil come out of the lower end falling.
Incense “smoke” is not just suspended ash from combustion.
Incense contains a lot of oils and the combustion is incomplete. Note the brown droplets of oil on the glass from the cross section. The smoke is so much heavier out the bottom because it’s mostly uncombusted oil in suspension.
If you were to trap and analyze the smoke from above vs below, you’d find a very different oil content ratio.
That might be true, but I doubt the post-it note has a significant oil content so that's likely not an important part of the effect.
you can also see the (what i suspect to be) oil condensating on the glass that the candle half is pressed against.
@@Manoplian Paper is not just wood pulp, there’s a binder component which is combustible and liquifies before burning.
“Heavy smoke” in general is a suspension of unburned fuel. You can light it and it will readily burn in most cases.
I'm guessing the oil/smoke contains some big heavy terpenes too
You can make a smokefall from burning paper. Does the same logic apply?
You are to things what Tom Scott is to places. You find things, explain what makes them interesting, then explain how they work, Tom goes to places, explains why they are interesting and how they work.
Well said!
I'm always ready for them, they're so consistently good that even if they title a video "Reading the Terms of Service" I'd be SO READY AND EXCITED!!!
Nice try, Tom Scott.
And instead of a red shirt, there's a red pipe!
Stop smoking so much :p
Tom Scott weirds me out
I’m in the fire service and we do a lot of fire science and learning about fire phenomena. The first thing we learn is all about pyrolysis. It’s a really interesting subject. For example, when any material reaches a certain temperature, it breaks the material down and the chemicals are released into the atmosphere which is, like you said, the flame part. Once this is gone you are essentially left with coal (assuming it’s wood that’s burning) and that will just glow because the gasses are burnt off. We sometimes come out of training runs and our fire kit is pyrolising. Within our initial course the light a fire with lots of timber sheets, they lay out a small section of carpet about 3 meters away and have 2 cups, one empty and one half full of water. Empty cup melts and half full one melts down to the waterlevel (this is to show how much water can absorb the heat) the carpet starts to release nasty looking gasses whilst curling up around the edges, after a while this carpet just bursts into flames even though there is a few meters separation.
A good demonstration is to heat up small bits off wood within a glass jar above a Bunsen burner (attach a tube to jar to allow the steam and gasses to exit away from the flame) at first you will get water droplets and then the smoke will come out white where it has a slight moisture content, this will then turn brown/green and this will be the flammable gasses. Once the process is over, the original wooden pieces are now just bits of coal ready for the BBQ.
This would be a really cool video and you can then demonstrate flashovers and backdraughts.
So, pardon me if this is a silly question, but is this coal, like, actual coal? I’d love to know how wood can turn into that. Or is it more briquettes that you’re making?
I also definitely agree about backdrafts. Probably the only thing Hollywood gets wrong because it’s more spectacular in real life, not less.
@@uzaiyaro He means charcoal rather than actual coal
PSA: Pyrolizing wood produces a lot of carbon monoxide, so do this outside, and try to burn off the gas being produced if possible.
dude! this is so cool! i'd love to see steve do a video on this!
@@uzaiyaro sorry, this is to make charcoal. The briquette are, I assume, made in a similar way but with a manufactured wood beforehand. Like moulded sawdust? I’m only assuming on how they made.
I used to do nosework with my dogs, which is a sport where the dog is supposed to pinpoint the source of a specific smell. When you get into that, you learn all kinds of surprising things about how and where air travels within a room (since it affects how the smell travels and how/whether the dog can interpret it). In some of the seminars, we used "smoke pencils" or "smoke pens" to explore what airflow does next to doors, in sunny spots, next to corners, etc. That's what these smoke experiments reminded me of.
"Sorry it's a really bad line" dad jokes on point, Steve, proud of you :)
I think I took mental damage from that joke. The dad joke force is strong with him.
Paused and came here to like this :D
I still don't like discord, but I had to wind back just to see that again
It got me good 😂
4:40
About the Mexican wave, or as we call it in the US simply the wave, I've seen a situation where there were two waves in the audience moving towards each other. I was genuinely tickled to see that the waves canceled each other out when they met.
Yes, in the US it's just the wave. Cancelling waveforms is how our noise cancelling headphones work
Or in Mexico where it's known as, "the wave."
@@gdemrakul2824 113 people who upvoted the original comment care.
@@DampActionRC I'm sorry, I replied to the wrong comment (I intended to reply to an irrelevant comment in this same video). I hope you accept my apologies. This effect you're talking about seems pretty cool. Maybe somebody caught it on camera so we could all see?
Done with steve mould as a result of this. Must RACE be a part of ALL things descibed by those from there? Gonna do the old english swipe left
This channel is freaking amazing. I love that it's never "and that's just how it works" - there's always "but there's something that didn't make sense..." followed by more digging. This is an approach and attitude that we need more of in society - never assuming that we know everything there is to know about a subject, being aware that there is always something more going on that we haven't figured out yet.
The misnomer Mexican Wave amuses me. It was invented in America, and from here reached our neighbor Mexico where it was seen on global television at the World Cup, so the rest of the world associated it with Mexico.
In America, we just call it "the wave." I don't know what they call it in Mexico.
The wave
I had honestly never heard it called “a Mexican wave”. Thank you for explaining what was going on
Brazil nuts.
Ah, I was confused about it being called that too since I've always known it as the wave. This makes sense though.
In Mexico it's called "La Ola" or "La Ola de Estadio" if you aren't into the whole brevity thing.
I have been thinking about this topic recently so thank you for this video - I'm a blacksmith and when I fire up my forge, often times smoke from the coals will cling to the horizontal forge table before very slowly starting to rise (or settling I guess). I figured it was due to the steel table cooling the smoke before it had a chance to rise. It looks quite surreal. This video makes me think that my case, the convection probably doesn't get to pull all the smoke up with it; as the smoke is forced out of the coal mound to all sides, it ends up too far away from the convection stream to get pulled up, and it gets cooled by the table and simply lingers for minutes.
Do you happen to have any video of that on your channel? It sounds interesting
@@Spiker985Studios I don't but I have been trying to capture it. It doesn't happen nearly as much in warmer spring weather as it does in winter
My own hypothesis is that it works similar to underwater brine pools. Some conditions allow the smoke containing air to get unusually super saturated and so denser, but also somewhat stable so once it meets normal air with its normal concentrations the two gas masses don't mix as easily/fast as they otherwise would.
My friend was showing me one of these a few weeks ago, and it absolutely blew my mind + had me completely stumped as to how it works. I'm so grateful for this explanation 😬
This was very interesting! I especially liked the comparison with crowds exhibiting fluid like behaviour.
This made me think of the terrifying scenario of crowd surges that often cause hell incarnate (eg crush injuries in festivals or a nightclub) but can be modelled fairly accurately with fluid dynamics. I didn’t expect to think about that so thank you for another great video!
Is there an upper limit on the size of smoke fall devices? It'll work on incense cones or rolled post-it notes, but what about something like a log with a hollowed core?
As the hole diameter becomes bigger, it will sustain convection currents more easily. Read about the Kaprun disaster.
hawk 7886, I've seen it happening with small logs too that had a hole or a crack. don't know about bigger ones, I just don't have enough experience with it
Your comment reminded me of this experience I had:
I remember where I almost saw this phenomenon: it happened whilst I was burning a heap of bamboo stalks!
I simply chucked them in a fire, only to be spooked soon thereafter by literal wooden bombs as the pressure inside the sealed cavities made the stalks burst vigorously.
So, for the next batch, I poked holes throughout the pieces which had sealed cavities, basically creating a long tube of very oily wood.
While burning, which wasn't easy at all, lots of dense white smoke oozed lazily out of the top, barely rising; I'm sure that, had I lifted the cane out of the fire, I'd have witnessed a smokefall out of its bottom!
@@SugoDiGatto Hmm... bamboo bombs in a campfire, you say? (Off to the lair!)
A glass bottle with a couple small holes in the bottom will allow this effect with an incense stick, but will stain the surface it's on.
Something i remember as a child is smoke from the chimney falling when there was a snow storm on the way. It was explained to me that the high pressure front of the storm forced the smoke down low.
don't storms typically have *low*-pressure fronts?
@@purplezart that would actually explain better the phenomenon, less pressure equals less air thus the capacity of it to suspend any particles would be diminished
It was just how it was explained to me as a kid. Not sure if it was right or not but i can tell you it almost always happened before a storm.
So im assuming its more like when a fire is just being lit or is small? but when its significantly colder outside and the flue/ chimney is cold once a fire is lit it can create a backdraft causing the cold air to sink in to the chimney, partly the reason for they flue so you can close it when not in use and if you ever noticed on cold days there can be a significant flow of cold air from a chimney if you don't have that shut. Will also cause the smoke when lighting up a fire to just gointo the room instead of out the chimney until it gets warm enough and enough upward heat and airflow to create a flow up and out. Its called the stack effect just as an FYI but as a side note something that's not commonly known is that when there are large atmosphereic pressure changes like storms it can also cause a net flow in or out of cave systems or underground tunnels.
@@connorjohnson4402 absolutely this.
It’s about fighting the cold dense air sitting on top of the chimney, like the upside down version of putting your finger on the end of a straw and into water.
We would have issues starting our fireplace if it was below 10°F outside. It would take quite a while for the heat (and annoyingly smoke) to find their way up and out.
Once again Steve, always with these interesting science topics.
I believe he gave credit in the end to someone else for the topic.
The post-it note example reminded me of years ago when I was a smoker. Break the butt off of an unburnt cigarette. Pull the cotton out of the paper of the butt. Then take the cellophane that's around the bottom of the cardboard box they come in. Turn the square shaped cellophane upside down and set it on a flat surface. Twist the butt paper into a thin paper tube. Light one end of that paper tube. Use the lit paper to burn a tiny hole in the top of the short side of the cellophane. Then turn the burning paper tube around and stick the unlit end into the hole you just made and let it burn. The smoke will flow from the paper tube to the inside of the cellophane and fall downwards just like the post-it.
I have a theory that maybe Steve knows about the cigarette trick and came up with the post-it trick because he didn't want to make cigarettes look cool which is a great thing. Don't smoke, kids.
As my niece would say... 'Eeuw!'
As people say smoking is harmful to you and people around you too.
Breathing in smoke but not smoking yourself is know as secondhand/passive smoking.
You can still get all the horrible diseases from regular smoking as well as secondhand/passive smoking.
Huh, I used to smoke but I've never heard of that!
I came to see if anyone knew about this besides me, but I can go one step further, if you'll leave the cellophane on the pack you can pull up down to increase the flow rate.
I absolutely love how along the way of learning about this cool new trinket I now want, I also learned two very cool things about smoke and burning, how the way we conceptualize them is only due to circumstance. Amazing insights!
I love thinking about things in completely new ways and you do a fantastic job at bringing that out!
Fire being the special case is a really interesting insight. Thank you for the great video
I've needed this video since Christmas when my dad got one of those! Thank you so much for explaining!
This is exactly what I was looking for. I want to make Backflow cones out of my regular cones and didn't know how far to drill the hole thank you for this video!
That's awesome! We always had neat incense burners at the local flea market, but I've never seen one that had a smoke waterfall! It's usually Grim Reapers and Dragons with smoking mouths and eye holes.
I have one that is a tree with a face in it. The smoke rolls out of its mouth
I got one that's like a mini pond with a water feature, the smoke fills the "pond" which has two koi fish in it.
2:34 I have never rolled my eyes harder than hearing "for a fixed smoke flux..."
Steve you killed me with "it's a really bad line" your humor is spot on XD
So many forces at work to make such a simple looking piece of art. Love it!!
The questions we didn't know we needed answered!
I've been using nag champa for years and I've recently purchased a few Japanese ones. They're so much better! My favourite so far is autumn leaves and I giggled when you mentioned it! The only downside with these is that you need to constantly replace them and have many unlit just there in the open air. Very subtle compared to harsh bamboo smoke. It doesn't stick on walls etc. But it's a good reminder that the scents are from wood and are not highly perfumed.
Great video!
This was described to me by a science teacher as creating a small vacuum or low pressure zone, where air is moving up but the smoke gets thick enough in the zone and so heavy enough to fall.
Very good 🙂
We have one of these and, today, I discovered something else weird about these incense cones. Try placing one on a flat-based candle holder (as used for ball candles, for example). When I did this today, I discovered that the smoke simply pools at the base of the cone. I've also noticed something about the smoke generated by these cones that may play into the physics - it seems to be much more oily than you'd expect (judging by the residues on our 'waterfall' burner) - which may play into the speed at which it cools down, as well as providing a greater density when suspended.
Fascinating stuff - good work.
Thanks for yet another great video! Maybe an idea for a future video: I have been wondering how blades cut on the molecular level. I.e. a very sharp blade does not need much force at all to separate a material, is there any particular molecular/atomic level interaction between the blade and the material being cut? Does the blade just wedge itself in between the target material atoms mechanically pushing them apart, or is there more to it than that?
I really appreciated that, "a lot of smoke is coming out of the top; it's just moving faster, because of convection, so it's harder to see." was reiterated into "for a fixed smoke flux a stream of smoke moving faster must be less dense."
I've never seen the excitability of bubbles quite so clearly, but I DO love watching the activation of those sodium acetate heat packs, and now I know what to call them!
Interesting fire moment I had recently: I had an overgrown ditch (steep grade) connected to a lawn that gets mowed. There was a mat of dried grass across the face of the ditch, and when I lit the righthand edge, the fire slowly crept across sideways, like a giant incense stick, until it reached the left hand edge, but the fire never moved into the mowed lawn, because there was no fuel, no mat of dried grass. Reminded me of the Forest Service’s clearcut lines that act as firebreaks, helping prevent widespread forest fires.
I once saw this effect with a lollipop stick, or possibly a q-tip that had had the cotton pulled off, when I was a kid. I have no idea anymore why it was set on fire, but because the paper was rolled so tightly into a solid tube, the inner hole was very narrow and the smoke came out the other end in a jet rather than falling out like a liquid. It was cool enough for me to remember it even now. Unfortunately, they don't seem to make those out of paper anymore, it's all plastic, so even though I've thought about recreating it several times, I've never been able to. Although it's not like I am constantly buying lollipops to see what their sticks are made out of, so maybe they are still around somewhere.
Paper lollipop sticks are still around for sure
Perfect timing. One of my friends just gave me one of these as a gift and I've been wondering myself. I love it!
Expanding on your notes around 7:15:
Smoke is flammable, for the reasons which you gave here. If one were to collect a bunch of smoke and introduce a flame to it (in a mixture of oxygen), then the smoke would ignite. That is why smoldering fires produce a lot of smoke but firey fires do not, I think.
He literally gave reasons why the incense smoke is not (so easily) flammable.
You seem to be talking about other kinds of smoke (smoke from recently extinguished candle) and thinking it applies to all smoke, and not listening to what Steve is saying really.
@@u1zha who asked
That “really bad line” joke was seriously the best joke I’ve heard in a long time. Brilliant, mate!
Here's another question for you: what causes the regular "puff-puff-puff" pattern of smoke coming out at 5:20?
Cool video! I've been wanting one of these things for a while, haha.
"puff-puff-puff" is the most perfect and concise way to explain this lol
I remember seeing this in a NightHawkInLight video almost a decade ago! Very cool effect.
7:40 Don't say it Don't say it Don't say it Don't say it Don't say it Don't say it Don't say it Don't say it Don't say it Don't say it Don't say it Don't say it!
5:51 this I used to do in front of the fireplace as a child.
I discovered when I rolled up pages of newspaper, the smoke would flow out the other end when I put the tip into the fire in the fireplace.
The smoke would then flow around until enough would accumulate and reach the flames where the gas would ignite causing the flame to travel to the opposite end of the newspaper tube.
4:14 "Ryan *Cummings"*
**insert dank trollface**
thanks for this video. i bought one of these for my wife and ive found it fascinating that they managed to get what i thought was hot smoke to fall
Fluid Dynamics always freaks me out.
It is easily one of the most complicated fields of mechanics;
even the _simplified models_ are hard to work with a lot of the time, and involve a lot of Navier-Stokes equations and things like that.
3:39 Thanks for the pick up line idea, Steve. "You shorten the refractory time of my excitable medium".
Weird, I just randomly came across these incense burners on Amazon the other day. I think it was the first time I’ve ever seen them, that I can remember anyways. I just assumed the ceramic burner had to be placed in the freezer prior to burning in order to cool the smoke to the point it would descend down instead of rise
I didn't even know these were a thing and I'm now learning more about them than I ever thought I would
Never seen one of these before but they do look really cool. Now I want one myself.
I learned how to make a smoke fall by rolling up the paper and tin foil from the inside of a cigarette pack then slipping the cellophane up on the pack so that the pack is only half in it cellophane burning a tiny hole in the cellophane and placing the role of tin foil and paper in the hole and lighting it...
I learned this trick in the 80s...
This is the first I've seen anybody try to give any kind of scientific breakdown of it.
Awesome job, thanx.
Also I didn't know they made incent burners that use that and I burn a lot of incense... this is an amazing find to me.
Today I learned: In the UK, "the wave" is called "a Mexican wave."
In Germany, it's _La Ola_
@@andrebartels1690 I am guessing that nobody ever says, "eine Mexikanische ola"
Which is a bit funny because it started at the University of Washington... in Seattle
We also call it “the wave” in Canada
It was invented in mexico where its called “la ola” which means the wave in spanish
Weird thing is... I feel like this entire episode is a promotional commercial on Back-flow incense burners. lol I've never heard of these until now and now I want one!!!
Great video! As always (in my extremely biased opinion), the more fluid dynamics videos the better. This whole exercise feels exactly like the kind of thing we'd get as a homework question for my Convection class during grad school fluid dynamics... so much so that I am really tempted to dig out my notes and textbook from that class, which is an expert example of nerd-sniping, so well done I guess. Anyways, I definitely agree that entrainment is the core reason why it "sometimes falls and sometimes doesn't fall". The combustion is heating the air around it, setting up a free convection flow due to the density differences, which then entrains air around it to flow too due to shear setup by viscosity. The area of effect around the plume of this entrainment acts in some ways similar to a boundary layer, at least insofar as the effect obviously diminishes with increased distance, though I can't remember what shape that "boundary layer like" entrainment takes, or if it follows the same sort of parabolic or log-law behavior as a normal boundary layer. (To get the plume shape I think you need to know both the momentum and thermal boundary layers and I think I remember that if you use a boussinesq approximation to simplify N-S you can analytically derive the thermal boundary layer profile, and that it is steeper than the momentum boundary layer). Anyways, get the tracer (i.e. smoke particles) far enough away and they won't be entrained. Or you can just block the flow communication entirely with a giant acrylic enclosure, which works too. I am sure there are dozens of fascinating CFD and flow visualization papers out there on this topic which can show in beautiful detail exactly what is happening (partly because buoyancy driven flows and free convection are fundamentally important in tons of applications, but mostly because buoyancy driven flows almost universally make stunningly gorgeous CFD or flow-vis videos).
A curious note on this... if you make a cylindrical wick (i.e. stick a piece of paper as a hollow cylinder in some wax) the smoke will get caught in the centre... to the point about the smoke fall in a stickey note working I wonder if its a matter of the heavy particles having somewhere too fall before they are caught by those fast moving convective currents...
Wait this was actually really cool. It’s crazy how we don’t question common but incredible phenomena like this 😅
I remember learning to make a smoke waterfall with..... Smokable products.... just by pooling the smoke in my mouth and pushing it out slowly. it always blew my mind. Thanks for showing me how it works!
😮. Does this mean that it is possible to create torches that don’t create soot on the ceilings and walls?
Propane lights??? Led lights?
@@tatertott2390 sure but I mean actual torches lit with fire. Is it possible to engineer a torch “handle” so that the smokes goes down like this… that’s what I mean. Bc you know how torches leave black marks on walls and ceilings.
When I was a kid we'd make them all the time with cigarette packets.
If you set a pack of smokes, lid down, and lift the bottom part of the plastic wrapping to create a square see through cellophane housing. Then we'd roll a piece of paper just like you did, use the burning tip to poke through the cellophane, leave it in, and watch the smoke fall.
I’d love to know where you can get such beautiful „smokefall ceramics“ as shown in the video 🤔
Just search for "backflow incense burners"
Any place that sells home decor should have them
4:40 What carrier do you use for that paper phone?
Can you fill a bottle with smoke and seal it? Will it stay in there forever if properly sealed? Could you create a "smoke globe" this way?
My first intuition is that it would just settle in the bottom so it wouldn't look like smoke in the bottle
@@benstanfill363 yea but it cant settle forever right? At some point it would fill up?
@@Jmdeleeuw- The smoke particles won't stay in suspension forever. You'll end up with a bottle filled with air and soot on the bottom.
@@AileTheAlien and if you rattle it about it’ll what’ll happen?
@@jasperwong2970 many of the smoke particles as they contain oil would stick to the bottom of the glass. And the finer ones would probably stick on top. So I'm guessing most of it would remain on the bottom. Interesting experiment to try though
I remember where I almost saw this phenomenon: it happened whilst I was burning a heap of bamboo stalks!
I simply chucked them in a fire, only to be spooked soon thereafter by literal wooden bombs as the pressure inside the sealed cavities made the stalks burst vigorously.
So, for the next batch, I poked holes throughout the pieces which had sealed cavities, basically creating a long tube of very oily wood.
While burning, which wasn't easy at all, lots of dense white smoke oozed lazily out of the top, barely rising; I'm sure that, had I lifted the cane out of the fire, I'd have witnessed a smokefall out of its bottom!
I had wondered how these work for a while. I had assumed they had to be cooled down in a refridgerator or they had an ice cube inside. Thanks for the explanation.
I'm glad you mentioned that KiwiCo doesn't just do subscriptions. I've considered getting something like this as a gift for my nieces/nephews, but the subscription bit always turned me off. I'm sure the subscription is great, but I imagine after a while boxes of these stack up and become clutter.
A one-off box seems like a nice way to give them (and their parents) a taste of what KiwiCo has to offer, before committing to a monthly subscription.
Kudos on your incense cutting skills, them blighters are so fragile 😆
I love how Steve went out of his way to describe the Post-it note - the same size and shape of a cigarette, with smoke at one end and a flame at the other - as just a rolled up Post-it note with the diameter of a pencil.
Pretty sure my videos prompted the invention of these things. I did a few videos on early TH-cam about making smoke waterfalls with rolled sticky notes and these popped up a short time later. People used to do a similar thing as a cigarette trick but I think it was forgotten for a time between the 90's and early youtube.
if you were on TH-cam in the 1800s then I'm inclined to believe you
@@ajazman7 If you know of these devices existing prior to 2013 tell me what to Google so I can learn about them. Far as I know that's the first time the sticky note trick took off on the internet, then a few years later I did a follow up video, followed by a channel called Giaco Whatever trying it with incense, and about a year after that they showed up on store shelves.
@@Nighthawkinlight The earliest patent of this thing I could find was CN201230066466.3 Patented 2012-03-20, Which the guy claimed he discovered it back in 2010. But I'm pretty sure I've seen something like this back in 2008 or 2009 at some random antique(and fakes) market in Luoyang, Henan. It's nice that you found this behaviour and posted a video about it, but there's only so much things to be found out by billions of human on earth. Claiming something to be your invention is a bold move and I respect that, cuz I've done things like this before and I still cringe till this day whenever I think about it.
@@solivictus Nice find! Beat my video by a year then. Note I did not claim I invented these, I claimed to have probably inspired their invention. Proved me wrong there. At least I still have claim for inspiring the Eggzer/Golden Goose.
@@Nighthawkinlight I too once thought others' creation was inspired by my finding, and turns out they figured that out by themselves, and I wasn't even the first one who discovered the mechanic. There's just too many human on earth thinking at all times 🤣. Hard to say who inspired who or who came up with it first.
Thank you for pointing out the pomegranate juice... I was watching it thinking it was a complex chemical reaction in lab glassware, as soon as you mentioned it I could see the Pom bottle.
Smoke gases are mainly H2O ( lighter than air), and CO2 (heavier), The visible parts are droplets and solid matter (heavier). Smoke cones evaporate a lot of oil, so the mix is potentially quite heavy.
How is water lighter than air and carbon dioxide heavier? Did you mean CO?
@@nerfherder4284 it's quite easy to estimate density of gases, it's proportional to their molecular mass. so, for water it's 18, for CO2 it's 44. average molecular mass of everything that air consists of, is about 29. therefore, water in gas form is lighter than air while CO2 is heavier. CO (28) has almost the same density as air
Why doesn't the oil ignite?
@@nerfherder4284 I know it's counter intuitive, but gas densities are proportional to molecular weight (each molecule claims the same amount of space in an ideal gas). O2 and N2 are 32 and 28 respectively . H2O, being an oxygen with two very light H, is 18. CO2 is 46. The whole thing is valid for H2O as a true gas; as soon as it condenses things change, obviously. Condensing water makes white smoke. I suspect the bluish smoke of incense is mostly essential oils. Air can carry quite a bit of water in mixture before it starts to condense out.
As a sailplane pilot you know everything about water being light; it's the main driver of stable thermals.
@@fewwiggle High flash point.
2:40 I was guessing that the vaguely conical shape of the hole acts like a nozzle to some extent? Pushing the expanding gas down, creating a draft with it that pulls most of the inside smoke with it ; the smoke you see emanating from the top is the part coming from the outside of the incense cone (perhaps)?
I used to do this as a little boy with printer paper. I still think smoke and fire are the most captivating thing.
Wait, but when you light incense there is a flame and you have to actively blow it out… so what sets apart a situation where a material can both burn and smolder? Is it that the open flame of a lighter is hot enough to vaporize enough fuel in the medium to sustain an open flame? Then when you blow it out, it continues to smolder because the reaction of burning isn’t hot enough to vaporize the oils for a sustained open flame?
Would some materials just contain certain oils with flash points very close to that of an open flame vs a smoldering reaction?
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Several things I hadn't considered before. Thanks very much. I'd imagine that the smoke falls because its not being caught up in the draft flow to the flames, partly because there aren't any flames, and partly because the smoke is released far enough from the combustion. As always, interesting stuff, told clearly, concisely, and with a sense of humor and wonder. I'll be back. 🙂
Thanks for the video - but Michael Faraday covered much of this - brilliantly - in his Ri Xmas Lectures on the Chemical History of the candle in 1848 (yes - nearly 175 years ago). His book on the lectures is in the public domain, and various people have tried to recreate his demonstrations on video (some are quite tricky to set up).
I have a copy! Of the 1926 printing.
Thanks for your reply but many people are unaware of M. Faraday's lectures, and he isn't around to demonstrate it!
@@agimasoschandir It’s sad that many people are unaware of Michael Faraday - and particularly the Christmas Lectures for young people that he established in 1825 whilst he was director of the Royal Institution. He is one of my science heroes. This year marks the 200th anniversary of his invention/discovery of the electric motor. The Xmas lecture series is still going strong, and they have been broadcast on television since 1936 - so are probably the earliest (and longest running) science programmes on television. Various people have repeated his lectures and demonstrations (some are quite tricky to set up, and others would be considered downright dangerous today). A quick search on your favourite search engine will reveal videos of them - and the Ri’s own channel has videos of many of the televised lectures (well worth exploring).
I literally just saw one of these for the first time a week ago and had no idea what it was. Thanks for the video!
This is the first time I've ever heard of it being called a "Mexican Wave." Which I think is peculiar... cause I'm Mexican.
Comes from people outside the US & Canada associating it with when it was first seen globally during the 1986 World Cup in Mexico City.
@@johnmcgimpsey1825 you go into a science video and end up learning some history.
@@johnmcgimpsey1825 For those wondering, it's apparently just called "the wave" in North America
The world needs a video from you on Ball screws
I wonder how many smokefall incense burners you just sold.
I'd like to buy one! I'm going to look it up on Amazon.
4:47 you have reached the pinnacle of comedy
Fill a medium to large glass up with warm soapy water and shake it around while your hand covers the lid with a seal. You will find a significant amount of air pressure whooshing out when you remove your hand. Do the same thing without the soap and you will find that there is not any significant air pressure created. It seems to me that bubbles are able to create pressure through tensile forces in a way that I don't think has been fully detailed by physicists. I think this could have implications on the scale of the cosmos. I know this sounds asinine, but I hope you will humor me if you are running out of ideas for more videos.
I experience this effect when making smoothies in a blender. I like them without soap so it is probably just the temperature difference between the cup and the ingredients which leads to the air changing their temperature from the cup's temperature to the ingredients' temperature.
Great video as always, btw I think the convection still happens inside the tube but its forced to compress and go out, cooling along the way and getting dense .
3:49 Why do you keep calling it a "mexican" wave??? It's just "the wave" or just "wave." I'm not sure what makes it mexican?
It's just a name that's popular outside the us for the wave
Loved the podcast btw, MORE MOULD!
I noticed the video didn't actually give a real answer but if you dig around in the comments you'll find one!!! 🤨
Finally a video on one of these that isn’t weird clickbait advertisement from a dubiously legal source.
Well, I can tell you right away why it's so weird, smoke usually goes up.
exactly
you just unexpectedly explained what fire is. god bless you!
I used to create smokefall's all the time when I was younger and smoked cigarettes' about 10 years ago.
I'd take a small, long, piece of a discarded cigarette box and roll it up really tight into a small paper tube, leaving just a small hole thru the roll. Then, I'd light one end on fire and blow it out to form a small tinder. Using that lit end, I'd make a small hole into the center-bottom cellophane wrapper still attached to the discarded pack of cigarettes, inserting the un-lit end of the paper tube into the small hole and upright. I'd then turn the whole assembly with the bottom of the box facing upwards, and slowly raise the delicate cellophane wrapper as it held the previously created paper tube, then stop just before it came off the box and watch as the smokefall hit the box and collected and the bottom of the pack of cigarettes.
They were always fun to watch and interact with.
With that hole in the middle, I'm thinking of solid fuel boosters that burn from the inside out, spewing hot matter below them.
Would it work even better if the incense was burned from the bottom/middle?
We used to demonstrate Brownian motion using smoke from a burning paper straw. You hold the straw at an angle to the horizontal and light the high end. As it burns the (waxed paper) smoke falls down the straw because it's actually heavier than air and being at the bottom of the flame inside the tube, no convection currents exist top push it upward.
(The smoke was collected in a dish under a microscope and viewed to see the motion).
A candle shows the same behaviour if you blow it out and it continues to smoke. As the wick cools and the convection currents stop, the heavy smoke starts to fall down the candle.
If you want to get into exploring convection currents, you might try setting up something for Schlieren photography/videography. Tons of fun and an excuse to purchase an expensive mirror!
My favorite way to do a burner is a mason jar. Large volume mason jar with a few holes poked in the lid allows you to observe the unperturbed flow from those cones. You need multiple holes in the lid to allow enough air to get a good flow
Hey Steve, I have seen smoke from chimneys go down, instead of rising. only on certain days, I think those days are generally very cold (below -20C) and calm, no wind. It's odd when it happens, and I have never been able to explain it. I suppose the cooling of the smoke going up the chimney would account for the falling smoke? Really interesting video, thank you
I have one of these incense burners and it's really soothing to just watch with some soft music on, when I've had a stressful day. I've always wondered what causes it to work.
So, I think part of the way this works in the post-it note, is that the hot gasses expand, right? So this creates a pressure through the tube, so long as the pressure in that tube (through being long enough compared to thin enough) is greater than that of 1 atm, there will develop a draft through the tube, and a pressure gradient with the highest pressure side being the end with the combustion, this ensures that the flow continues to drift through the post-it note from top to bottom. On the top side, any gasses that are made that are not into the tube obviously dissipate freely into the surrounding air, and so the draft follows normal convection expectations.
You should be able to test this sort of thing with a water, a heater, and a tube. Heat the water at one end of the pipe and then you can use drops of dye to see where the water is moving from convective currents. I suspected, if the heater is in the pipe, while some dye will come back out the end, a flow should build pulling the water down. One would probably have to play with the parameters though: width of pipe, length of pipe, temp of heating, etc. Since not all parameters could generate a pressure greater than the end side of the pipe. (Perhaps this should also be noted it should flow more if the pipe is straight level, rather than deeper.)
My guess is heating water will only cause upwards draft through the tube... Thermal expansion of water is somewhat tiny.
The downwards flow through the post-it is dependent on the fact that gas expands a lot, and additional gas is created due to paper burning.
@@u1zha good points!
Have you ever investigated adhesion in smoke? I know most basic cotton clothing seems to display an interesting "Stickiness" as smoke passes over it. Now I'm wondering how other materials display this...
Thats the first time I'm truly tempted to do patreon for those live Q&A
Years back I picked up a wine bottle that was modified to be an incense burner by having a couple holes drilled in the bottom. An incense stick would be suspended in the neck of the bottle by a key ring, and the smoke would drift out the holes at the bottom. Unfortunately, the oils would also thoroughly stain the surface it was on.
6:24 but what if that bent copper pipe is a much more effective heat sink than that metal lid you were holding before? You ruled out the heat sink effect of that lid, but the copper pipe may be effective enough that you mush consider hear sink properties a factor again.
It is like folk do not observe what they see, I for an example have seen smoke low to the ground rather often and even in the photoage at 1:54 you can see smoke falling down the hill so the trees below are covered up to the tips. So for me smoke just follow the air, so where the flame is located it goes up, but if the smoke come to coulder air it will think to the bottom, so in a room with a good average temperature that have same temperature at the top and bottom the smoke would spread evenly.
And air work a bit like water, if you have a container with room temperature air you can then pout could ait into it, it will follow the same path water would take and start to fill up from the bottom.
Like if you do not have a container you have all the turbulent air around you, the more turbulent the air is the less chance there is that it will go straight down, it will thin out much faster, a bit like a smoker exhaling smoke, so when you place that thing on top of a container there is no turbulent air, that thing is so porous that the flame suck oxygen through it rather from the jar under, so the smoke come out from the underside is just coulder and sink to the bottom where it is then wanted out on the bottom, like a house on fire until you open some holes at the top above the fire.
Or have I missed something, I am not very well educated so I may be totally wrong, If I am, pleas educate rather than make a angry comment.
Some people would see these and say, oh neat. And move on.
It's nice to know I'm not alone in exploring curiosities! Thanks for sharing, Steve!