Revealing The Hidden Secrets of Experiments (using Schlieren Imaging)

This levitating lighter trick is so incredible that it's almost difficult to believe. But using Schlieren imaging you can easily see how this works. And in today's video I'm going to use this special imaging setup in my garage to test out a bunch of cool experiments that look even more amazing when you can actually visualize elements that are normally invisible to the human eye. That and I'm going to test out a bunch of random objects just because it's fun. There's plenty of other videos that explain Schlieren imaging better than I could so I won't go into much detail but I will show you the basic setup so you can see just how easy this is to do for yourself. First I taped a piece of aluminum foil over the flash of my camera and poked a tiny hole. Then I turned the flash on and placed it in front of a telescope mirror at the right distance. To find the exact distance away from the mirror I need to look for a tiny dot of reflected light. You can see that dot here on my finger and I want to place the camera where this dot is the smallest and therefore the most focused. Once I do that and it's aligned well enough I just have to lock the camera's focus properly and that's it. Now when I put something like a lighter in front of the camera you can easily see the butane and it looks quite beautiful. When solid objects are placed in front of the lens they directly block that light and you see a silhouette. However when something transparent with a different density like butane is in between the light refracts as it passes through and that change of direction causes some light to miss the lens resulting in the distinct dark outline. That's enough background from me but I intentionally skipped some more specific steps because I followed this YouTube channel's tutorial and I think it's fair for you to check out their more complete guide if you want to do this yourself. Anyway now it's time for the fun part which is trying out a whole bunch of stuff. First let's start with a few classics. Here's what a heat gun looks like on the low setting and if I switch it to the high setting you see the forced convection moving even faster. Next here's a matchstick striking a matchbox and yes I did briefly forget the fire was hot here but I was fine and the shot looks great in slow motion so it was well worth it. Next some compressed gas. This is from a can of electronics duster and it looks pretty cool. However a much more amazing compressed gas demo is using compressed air from a tank. I've got a few different nozzles to try out and just for reference the air will be coming out at around 90 psi. With the first nozzle you see some beautiful shock diamonds. Shock diamonds are standing shock waves and are perhaps most famously found on supersonic jets. Although those obviously look much cooler this is much simpler and is still awesome. I also tried it out with an inflation needle like you'd use to pump up a ball and I was surprised to learn these haven't gone up in price that much over the years. Anyway this smaller nozzle still produces some standing shock waves but it's definitely harder to see. I used the last attachment which had a medium sized nozzle relative to the two others and this was pretty solid too. I already briefly showed what both regular and long neck lighters look like when the butane is coming out and when the gas is ignited but here's what a larger spaceship torch looks like. I was a bit surprised that just releasing the butane wasn't that visible because it seems like so much is coming out. However once ignited you can tell it's very hot and is pretty impressive. These torches are refillable but sometimes it feels like some gas leaks so I decided to test it out and I definitely spilled quite a bit more than usual but it made for a great shot. And here's the best part again in slow motion. The last torch I had was this triple flame and it also looked decent. Next here's what a candle looks like when it's burning and I also tried to do the classic relight the candle from its unburned wax paper trick. I've shown this before and since you don't need to see it it makes sense that watching this using these special optics didn't add much. But oh well. Next here's some boiling water that I poured into a shot glass and you can see it a little bit but nothing too impressive. You can also see the release of carbonation from sparkling water which I'm pouring in here. Doing yet another sparkling water experiment gave me some flashbacks to one of my most recent videos but nonetheless I did enjoy seeing this one since I didn't think you could see as much action as you did. Speaking of CO2 I also tried out some dry ice which is extremely cold and here's what a piece looks like when I hold it with tongs. When you place dry ice in an empty glass the CO2 is heavier than the air and accumulates in the glass as the dry ice sublimates. That means you can tip the glass slightly and CO2 pours out to extinguish nearby flame. I also placed some dry ice in a beaker of water so that it would bubble vigorously and this looks pretty cool although it's basically just a silhouette. Next I wanted to pop an even larger CO2 bubble so I threw some dry ice in a balloon. After tying it I waited a few minutes for it to inflate. Then I took a lighter and burned a hole in the balloon so it would pop despite not being filled up that much. As you'd expect the pop happened quickly but there were a few cool frames that I captured showing the gas exiting the balloon. Next hand sanitizer is pretty volatile so I wanted to see if I could see that with this setup. Once I squirted some out onto a dish I didn't see much so I lit it on fire and that looked pretty cool. Normally you can't see hand sanitizer in daylight but schlieren imaging isn't required to see it burning. You just need to turn off the lights and the blue flame becomes quite obvious. It kept burning for several minutes and I thought the final moments were the coolest because it slowly died down and then I love how everything went still so abruptly once the last bit was burned off. Next here's a deodorant spray which again you don't need schlieren to see but I think it's still pretty neat to see the darker silhouette of the mini droplets. Next here's a recent demo from the season 4 premiere of 2 truths and trash which is this flammable spray. I won't spoil that episode by giving you any more details but it looks pretty cool. I like how you can see the flame outside of the mirror's circle because of the light produced by the flame itself and it gives you a reminder that the objects are just right in front of the camera a few feet away despite it looking like it's on a projector or microscope or something. Twisting an empty but wet water bottle to a high pressure and then releasing it creates some fog and here's what that looks like. The abrupt drop in pressure drops the temperature which creates condensation. One of the first objects I ever made a video on was this induction heater which can heat magnetic and conductive objects extremely fast without the coil itself being that hot. It can get this fork to red hot temperatures in about 30 seconds or less. I tried this first with the screwdriver and you can definitely tell it's the screwdriver that's getting very hot while the coil only gets mildly hot. Once the screwdriver's out of the way you can still see that the coil's getting a bit hot. Drying it out with the fork and you get a good view of the convection currents off of each hot prong. Next here's me dropping an alka-seltzer in a small capsule of water. As the alka-seltzer dissolves it releases carbon dioxide. At first there's only a bit of gas being released and some droplets going up in the air but once it starts to bubble over there's once again some cool CO2 pockets that create nice visuals when they pop just like the dry ice in water. I also crushed up an alka-seltzer on a flat plate and then added water and this was a bit more chaotic. I tried burning some steel wool hoping to see a bunch of mini convection currents but the whole thing got so warm that it only really produced one. Next I wanted to test out a confetti popper and I wouldn't say it disappointed but it wasn't that amazing. Here was another slightly larger one with the trigger. Next I tried these poppers that explode when you throw them on the ground. First I tossed one. Then I tossed a few. Lastly I threw a bunch a couple of times. It looked alright but definitely not better than just a regular slow motion shot. I also wanted to try an arc lighter and an exposed tesla coil. The arc lighter was kind of mid but the exposed tesla coil was really cool. It wasn't perfectly centered so I moved it around a bit but it definitely doesn't look as cool as it normally does since you can't see the electricity which is probably the best part. Next I wanted to go over the davy lamp but it does require a little bit of background. I've shown before that if you release butane from a lighter without sparking it you can ignite that source of butane from a different open flame and the flame propagates back to that nozzle and continues burning. If I do this again but place a mesh in between the two lighters something cool happens which is that the butane flows through the mesh and can be ignited but the flame doesn't travel back to the nozzle of the lighter and instead is stopped by the mesh. The metal mesh acts as a heat sink that cools the flame temperature to below the ignition temperature of the gas on the other side of the mesh. Although this looks especially cool under schlieren imaging it was more than a fun discovery and created the invention of the davy lamp which is a lantern completely surrounded by metal mesh. The goal of davy lamps was to improve the safety of miners. Normally if you were working in a mine with an exposed lantern and you stumbled upon a gas leak it was gg. However with the davy lamp only gas that made it through the mesh was ignited and it didn't spread. Flame propagation in general is really interesting to me and here's a few random shots that I got while messing around with it. I think it looks especially cool in slow motion despite the limited 60 fps of the telephoto lens on my camera. During a test with the torch I also noticed something interesting. Which was that I couldn't really light the torch by releasing the butane in the same way and it would often even extinguish the flame. I tried this with a candle and it also extinguished it which surprised me. Only if I barely release the butane will it ignite and travel back to the opening. Speaking of surprising demos involving flame stability I got quite a few more clips of the levitating lighter trick. To turn a regular lighter that burns like this into a levitating lighter you have to remove the safety guard and apply some pen ink. To show the difference in flow that adding the pen ink causes here's a clip of butane coming out of an unmodified lighter and then after adding some pen ink here's what the new flow looks like. I should say this is one example of what it looks like it doesn't always come out that diagonal and does change as you use it but you can definitely tell it shoots out a bit further. Adding pen ink is technically all you need to do but I will say from experience that it works better with these lighters compared to the more typical BIC ones and as you might have already guessed you have to experiment around with the nozzle flow and the amount of ink to get it to burn perfectly. Sometimes it doesn't look like it's going to work and then shoots off all of a sudden and this one was quite stable even pretty far away from the lighter. If the flow is just right the flame is quite stable even when you rotate your hand quite a bit. And lastly the moment we've all been waiting for the dual welded levitating lighters. I was struggling to get both of them stable but once I did as expected when you cross the streams the flame retracts back to the point that it hits. Doing this kind of reminded me of that one scene in Harry Potter. Anyway I hope you enjoyed this video as much as I did testing things out. If you've got any suggestions that you want me to try out let me know in the comments and I might make a follow up. Thanks for watching to the end and I'll see you next time.