Experiments to Make Self-Cooling Fabric

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In this video we follow a paper that describes achieving a daytime radiative cooling effect on cotton fabric through the growth of CaCO3 microspheres directly onto the fibers. The paper can be found here: doi.org/10.101...
My previous video in this radiative cooling series: • Making Infrared Coolin...
Thank you so much to those of you who support this channel on Patreon! Your support really helps give me confidence to spend my time researching projects that are of value for more than just video views. Shoutout to my top patrons: Eugene Pakhomov, Peter Gordon, Evan Hughes, Teague Lasser, Matthias S., Michel Pastor, PabloXIII, Parker Jones, Simone Chiesi, Steve C, Yanko Yankulov, Walter Montalvo, Carl Katzenberger, Damián Arrillaga, Dan L, Edward Unthank, Gusbear, Jon Hartmann, Kejie YU, Kirk Werklund, Lisa L, Mark Roth, PabloXIII, Santiago Perez, Steve C, Thibaud Peverelli, Tristan Tonks, WilSkarlet, Yanko Yankulov, and Matthew.
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Thanks everyone for watching!

[@fearisan]

Kudos for covering a "failed" experiment the way you did! It emphasizes that an outcome is a valid outcome no matter if it was negative, positive, expected or unexpected. Imagine where the world would be if scientific papers were published like that. I think I might have to join your patreon just because of this. Keep up the excellent work!

[@eugenetswong]

I completely agree that publishing negative results is very useful. His methods are very credible, which means that we can tweak his methods or just move on to something else more promising. We don't need to repeat.

[@thirtythreeeyes8624]

The testing apparatus might be flawed, it looks like the temperature is being effected by the background paint. The thicker coating the large fabric got also doesn't look nearly as good as the small scale I think it needs more treatment and agitation with more room to stir in. While it probably wont ever be as good as the paint it looked like the small scale experiment showed there is some promise if the technique can be perfected. It's also winter and even if it's only 2-3C difference in the heat instead of the 5C of the actual paint your body is going to be able to cool down a lot from that.

[@app0the]

@@thirtythreeeyes8624 inre: the winter side of things, I think a halogen fixture could also be pretty useful for the experiment since they put out a ton of infrared (iirc even more than incandescent bulbs?)

[@VR_Wizard]

The failed experiments are actually the most exciting ones. Why did it not work, what property changed from having it on a flat surface vs having it on a rough fiber like surface? Could it be that the heat rays are traped inside the rough surface bouncing around never leaving it? When using isolation on your house rough surfaces are less isolating then flat ones I have heared which would sugest the opposite of what the experiment showed because that would mean the rough surface radiates even more heat than the flat one.

[@Surms41]

That's exactly why I love youtubers that post "failure" of a positive outcome. It removes a lot of guess work :) I like Jayz2Cents* in the computer market, as well as gamer's nexus.

[@Impatient_Ape]

Ben is showing how to do ACTUAL science on this channel. Excellent work!

[@TheFredmac]

This is what people go to engineering school for.

[@claytonharting9899]

+

[@choahjinhuay]

Not just melting lipsticks….

[@unything2696]

As a chemist with years of experience in crystallography, synthetical as well as analytical: You are doing great! There are always so many variables, but you seem to have built a good intuition already. Respect. Maybe the poor performance is due to the geometry of the fiberes? Even If the spheres reflect the light, the probability of it getting absorbed in the 3d structure of the fabric is just too high.

[@3nertia]

Hey, with your expertise, would it be alright if I discussed something with you? I have an idea but I lack the necessary knowledge to properly evaluate its viability

[@unything2696]

@@3nertia I'm intrigued already:)

[@MisterNohbdy]

that was my first thought upon seeing the results, though I'm no chemist

[@3nertia]

@@unything2696 I thought maybe, with CRISPR, glass sea sponge DNA, and DNA from a very specific fungus on Fraser Island, Australia that can turn volcanic rock into dirt, maybe we could potentially grow super-efficient solar cells that can convert way more than just UV into electricity I thought we could maybe use a similar method to grow carbon nanotube structure in various simple shapes as well ... Thoughts? Would this even potentially be possible or am I just an idiot? 😅

[@supernoodles908]

​@@unything2696I'm thinking testing different fibres might be a good idea. Cotton and plant fibres are "smooth" and don't open up much so it's hard for the microspheres to bind to it. Something like hair/wool night be good since the hair structure is scale like and can open up with warmth so you could mechanically trap the spheres on the hair

[@Pyrosparker]

"Even in the failures, we're learning things" That's what separates a non-satisfactory result from a true failure; if we learn anything then it's just an extra unanticipated step towards success. The process of making something interesting and useful with home-brew is already a great thing to share, and the extra effort of trying to make it easily accessible for the average-joe is on another level that I really appreciate.

[@Pope_]

As others have pointed out, the lack of radiative cooling might be due to the geometry of the cotton fibers at a microscopic level. The chance that heat radiated from the fibers will actually exit the cloth is much lower than the chance that the heat will get stuck in the cloth and continue to bounce around. I think all things considered it may be worth trying a fabric like Denim or Silk, which has a much tighter-nit structure at the microscopic level. It might also be worth trying to apply the solution to only one side of the fabric, as denim and silk both have flat faces compared to cotton, meaning it may be possible to apply the solution explicitly to the outside of the fabric.

[@aidanwarren4980]

Denim is cotton

[@Pope_]

@@aidanwarren4980 cotton which is structured differently on a microscopic scale.

[@BIGGGY305]

what if he brushed the fabric one direction a few times? just to test

[@kbee225]

Yeah but there should still be SOME effect. There is a section of space for every thread that can emit photons back without intersecting another thread. So it should have some cooling compared to the control piece he used. But they were identical.

[@kbee225]

@@BIGGGY305 What would that accomplish? This is a woven fabric. You can't orient the threads by brushing them.

[@danielhakamaki7678]

This story is such a rollercoaster. I was on the edge of my seat. Emotionally engaged by a damn chemistry video! I actually said "Noooo!" out loud at the reveal of the last experiment. In my own headcanon, "Electricity Free Air Conditioning" is the first part of a trilogy. It brought such new hope. Could this finally be it? A (partial) solution to a warmer climate AND rising energy costs. Why isn't everybody using this already? It's so clever! Then came the highly anticipated sequel, "Experiments to Make Self-Cooling Fabric", or as I have come to think of it "The Entropy Strikes Back". It was glorious. Jam packed with excitement, drama, ups and downs, glimmers of hope swiftly dashed, and an ending with both a punch in the gut and a thrilling cliffhanger .With pounding heart, after the video finished, I had to calm myself down. Of course it was to be expected that our hero should face fierce resistance, that the forces of darkness (or in this case hotness) must seem almost insurmountable. It's basic storytelling practice, so don't sweat it. If I know anything, it's that the hero always wins in part three. Really looking forward to "Return of the Infrared Dye".

[@figueroalabs]

Cotton fibers are single cells that get elongated and stretched inside the seed pods, so this is the reason why they look kinda like transparent plastic straws, or like transparent long tubular leafs of grass (which are multicelular, I'm just saying they look alike).

[@drworm5007]

Mammalian hair is also transparent when not pigmented. I have a long beard and have often noticed the lighter coloured hairs are clear. It's not surprising to me that cotton fibres would be the same.

[@Emolovesblack28451]

Don’t forget to link your other videos that you’re referencing! You’re the reason I joined patreon and I’m so proud of you. Your experiments are useful and interesting, and your processes are consistently well documented. Well worth crowdfunding.

[@Nighthawkinlight]

Thank you!

[@Skapo]

As a Texan, I approve of this research. 🔥🔥🔥

[@custos3249]

Especially after your state denied the right to water breaks

[@ugwuanyicollins6136]

As a Homo sapien sapien I approve

[@jessehunter362]

@@custos3249the cooling fabric don’t really help that all that much

[@grugiv]

it's nice when the power doesn't go out

[@jessehunter362]

@@grugivTbh as long as you manage things properly it’s fine even when the power does go out- i didn’t have ac for the first decade of my life

[@cineblazer]

We're one step closer to the mythical pillow that's always cold on both sides. Keep up the good work, I salute you 🖖 EDIT: even if it didn't work as well as you hoped, I bet you find a way to fix it. If there's one thing I've learned from watching this channel, it's that it's never a good idea to underestimate NightHawkInLight!

[@wingnutbert9685]

😁👍👍👍 Once perfected, then coat in his water proofing mix and we'll have sweat and body oil proof pillows too!!!!

[@deepbluetree]

This is what dreams are made of! 😍

[@deepbluetree]

This is what dreams are made of! 😍

[@Jmr2urbo]

This would be great for hardhats too. They trap heat and get very uncomfortable over time. Even if you had to reapply every now and again if it keeps my head cool it would be a game changer.

[@Nighthawkinlight]

My current paint could go on a hard hat as is. I'm thinking about trying that soon just to get one practical item made to test out

[@stephenrosenthal5252]

I too wear hard hats. Not everyday but sometimes. My thought was that they are keeping the body heat in. Not absorbing the heat from above. I mean moat of them are yellow or white anyway. My guess is that a test with your paint on the hat with no ones head in there might look like a success. Just for some one to put it on at work just to have it feel the same as with no paint. I think i feel like i saw a fan that could go in the hat. That along with some vent holes might be a better option.

[@TheFredmac]

Where this concept is most needed is in power line tree trimming. You can't have vents in your helmet working around power lines. If you can show that this helps cool a helmet I know people who would want to hear about this.

[@stormthrush37]

​@@NighthawkinlightI'd definitely like to see that as your next video!

[@babybalrog]

@@Nighthawkinlight My understanding is that you can get surplus hardhats for the cheep. They are only rated for 5 year lifespans so companies are constantly throwing away old ones.

[@Coldzillaa]

I love this CaCO3 series, i'm in the last year of my chemistry masters and my project this year involves synthesising CaCO3 microspheres (vaterite) for drug delivery purposes. I'm hoping to apply for a PhD with my current supervisor and exploring new applications. This work is excellent and i'm looking forward to seeing more!

[@Nighthawkinlight]

Very nice! I've read some about drug delivery uses for the microspheres. Are you mostly looking to absorb chemicals into solid microspheres or are you making hollow ones? I've been interested to try some modifiers to my microsphere recipe to see if I can reliably make them hollow. Sometimes a few of them are hollow just by chance, but additives like guar gum are supposed to help form them that way on purpose.

[@hiperkinetico2011]

@@Nighthawkinlight Being able to generate drug delivery would be interesting. Liposomes are currently used for drug delivery. Are these calcium carbonate spheres not toxic at all?

[@putteslaintxtbks5166]

Back in the 1970's or 80's I started seeing things that changed colors by temperature like mood rings and digital temperature strips for monitoring aquarium temperatures. If a roof/exterior could change to a dark color in winter and a lighter color in summer, it could make a big difference in heating and cooling a house.

[@ugwuanyicollins6136]

Are you I your late 60's

[@putteslaintxtbks5166]

@@ugwuanyicollins6136 Yes. Will be 67 on Monday.

[@DavidSartor0]

@@ugwuanyicollins6136 Why do you ask?

[@ugwuanyicollins6136]

@@DavidSartor0 they where alive during the 70's

[@DavidSartor0]

@@ugwuanyicollins6136 Thank you for responding. Obviously they are in at least their 60s. Given that, why did you ask?

[@FireNLightnin]

I've been watching for over a decade and I didn't even notice your videos getting longer. I'm always just so happy to be learning along with you.

[@nicholasswaffordece1215]

Thank you so much for posting this to the public. You are a true hero!

[@handyreiter1310]

Unimaginable that this kind of work was once attributed to universities! ❤❤❤

[@Science-Vlog]

SAY MY NAME!!!

[@cardboard8206]

Your failures only show your successes to be that much more legitimate. In the world of sensationalism, your honesty is invaluable. Well done!

[@TriAngles3D]

He consolidates so many areas of interest... Things that we would want to look into but usually never seem to get around to. And, then he takes it to another level.

[@richvasquez8960]

my wife has watched you for years and was raving i should check your channel. i think i will be raving about your channel more than she does. extremely impressive content. what an exceptional teacher. top notch sir!

[@MrAlFuture]

I, for one, really enjoy the longer form videos that cover a full project story arc like this does. I appreciate that it may not attract as many views, but they are really enjoyable, satisfying and inspiring to watch. Thank you for sticking with it and not giving in to the algorithm.

[@cleanroomwizard2356]

This is phenomenal work and I do appreciate that you provide the "null" result - something most scientists don't even bother publishing. It honestly saves so much time for others as well so they don't think that they are crazy or just doing something wrong. The key here is that everything is transparent to IR if it is thin enough and the amount of reflection of visible light and near IR may be not sufficient with these coatings (given that you had quite thick paint layers earlier to get ultra white cooling effect). As someone who has actually tried and replicated your pigment recipes, I deeply appreciate the level of detail you are putting into this series and my last suggestion is to consider that perhaps the amount of energy lost to space/cooling effect is completely dominated by conduction/convection to the air in your chamber due to the massive surface area of the fabrics compared to the painted panels (so you just end up seeing near ambient temperatures). That is another factor beyond just the actual pigment properties - a complex question with multiple possible answers.

[@Nighthawkinlight]

Thanks for the effort of trying my recipe! Did it work out for you?

[@cleanroomwizard2356]

​@@Nighthawkinlight Yes, it did! I have been trying to get smaller spheres than the standard recipe because the scattering efficiency is best when particles are approximately the size of the light that you are trying to reflect (so I would prefer spheres in the range of about 0.5-2 um to compare) but I don't know if it is the gaps or the particles that will dominate that behavior. I am going to try to add extra nucleation sites with a bit of fumed silica and a much more dilute solution to try and reduce sphere sizes. It is a project that is actively being developed this winter. I think a different polymer binder with more elasticity is also on my to do list. I greatly appreciate your heavy lifting in the other aspects of this work!

[@Nighthawkinlight]

Thanks for the report! I'll also be working on reducing sphere size soon. The first idea I'll be trying is increasing the citrate to lengthen the effective window where stirring time creates nucleation sites. You might then be able to effectively stir between 30min-1hr instead of 1-10min. You should also read the paper I link to in my previous video about size controlling the spheres. They had some interesting methods using I think ethylene glycol

[@cleanroomwizard2356]

@@Nighthawkinlight Sounds promising! I definitely think that has potential and will go in more depth in some of these alternative methods to tweak the formation/size of the crystals. My blender size isn't quite right for making large batches yet and I may try to invest in some type of centrifuge or else settling times of the smaller particles would be far too lengthy to be practical. I'll look forward to your next video on this topic and hopefully I'll have some interesting results to share too. Regrettably KZbin doesn't like links in comments to share other work/information but there are some other papers on these cooling materials to help determine predict best shapes and sizes of gaps/particles. The manufacturing difficulty, costs and durability tends to be the primary limit in my experience.

[@LeruaEcke]

yes i wanted to add a comment about this reflection too, so i just want to add that in many ways the fabric is not directly comparable with the painted plate. For example because the fabric has a different surface, and a different heat capaccity/ transport..

[@Rubikorigami]

Plant fibers like cotton are relatively finicky to dye and coat. Maybe you could try with wool : its fibers have little scales that can be lifted by chemical processes and trap the microspheres.

[@FLPhotoCatcher]

I like that idea - too many synthetic materials in our world that make toxic micro-plastics. And the wool market could use the help.

[@JP-xd6fm]

It will be funny saying in a hot summer day "I'm going to wear the wool shirt today, it's very hot out there" lol

[@VoidVagabond]

​@@JP-xd6fmmerino wool is typically pretty breathable and moisture wicking, so in that sense it would be an acceptable summer fabric.

[@JP-xd6fm]

@@VoidVagabondOh I didn't know, wool is used only in winter in my country

[@VoidVagabond]

@@JP-xd6fm my country too I reckon, I've just been researching fabrics and merino wool came up. Merino is a special kind of wool that is softer and finer and stronger compared to other wools.

[@adambruley5242]

You are Absolutely my HERO!!! We all love you... Keep us Experimenting and Learning

[@uhitsethan]

it might have more to do with the texture? when light bounces off a strand of fabric, the light isn't likely to bounce in the direction of space, but rather into another strand, then into another strand, etc.

[@Roshkin]

I want to see him try treating a sheet of cellulose to see if it responds any different.

[@TeamRiceUSA]

Exactly ! Just what I thought. Paul

[@FLPhotoCatcher]

@@Roshkin You mean paper?

[@tylerswan491]

Exactly my thought. If any photon bounces off a sphere it could go in many directions. Especially if it hit a bottom fiber. Now that photon bounces up and hit the bottom of another strand and now its bouncing around inside the fabric instead of escaping in a few bounces like a flat sheet if paper or something. (I dont know science)

[@papydoctor]

Yes, i was wondering also about the sample depth, front bouncing/emitting is ok but what happens at the middle/back of the sample?

[@blurglide]

I have a "cool" radiative cooling anecdote for you! Last weekend, I took the black soft-top off my Jeep. I thought I'd hose the dust off before storing it for the winter. My grass yard slopes slightly to the northeast with an unobstructed view of the sky, is shaded to the south by my house and a large tree, and the outdoor temp was 45 degrees. An hour later, I discovered that the mositure on the fabric had FROZE, and the outdoor temp had only dropped to 43! For similar reason, this portion of my yard retains snow for many days longer than anywhere else in my neighborhood. I've had tiny patches of snow around on days where the temp approaches 60, although not for long.

[@Nighthawkinlight]

The effect you noticed is actually responsible for some occurrences of black ice that occur before other things freeze

[@IdRatherBeMaking]

You may want to consider stirring the solution and cotton test piece under vacuum. You may have fibers that are bordering or surrounded by trapped air. That may be causing your lack of spheres on some fibers.

[@Adskdnweotland]

good point! maybe adding a surfactant could help eliminate bubbles during stirring

[@petersvideofile]

Fantastic work man. I love your enthusiasm, and the depth you get into, all while keeping your work understandable and accessible to anyone!

[@aquelaquelaquelaquel]

This is what education should be about... I am amazed with the quality of this content and long dedication. Love your work! You and VSauce are my favorite content on Ytube. I really loved the ride and the fact that even though the results were not so promising.. it is still uploaded so we can learn and live the discovery and a-ha moments!

[@paulwright8378]

You should view movie recaps 😂

[@ThingsWhichArentWork]

Thank you for sharing your work and your results.

[@MaxWithTheSax]

It is really cool to see the microspheres stuck to the fibres under the microscope. One thing I am wondering is what the expected result on the thermal camera should be. Since the coated surface radiates more shouldn't we expect it to show up warmer on the thermal camera? Maybe the difference we see is due to the insulating properties of the fabric versus the painted tiles.

[@Nighthawkinlight]

These coatings don't radiate *more*, they just radiate at a particular wavelength. If the radiative properties are working they will cool down, and the IR radiation follows the same downward trend with temperature as anything else causing the camera to read them as colder. I've checked the IR readings in past experiments and compared with thermocouples to see how much variability there is between camera readings and actual temp. When reading differences in temp between two samples in the same frame it's very accurate, unless trying to measure a very dissimilar material like paint vs polished metal.

[@RandyCampbell-fk3pf]

​@@Nighthawkinlightit might be that the cotton itself is just too insulative

[@Rin-qj7zt]

@@Nighthawkinlight any way to confirm the wavelength they are radiating at? only thing i can think of is that either the cotton doesn't transfer it's heat very well to the coating, or the structure of the fibers woven into a fabric does something to counter the cooling effect, like trapping radiating light. how well would the coating absorb the wavelength of light that it emits? in woven fabric, would the majority of fiber surfaces be more exposed to a path to direct air or to other fibers?

[@Nighthawkinlight]

@@Rin-qj7zt I have a plan for more accurately determining the IR wavelength that I might play with in a future video

[@CrustyBiker]

I speak as a simpleton who doesn't have any scientific knowledge but I'm just wondering if it's possible to get the crystals or whatever it is to grow on the sunny side only by maybe pat pressing the solution on or putting into a fast flowing river of solution one way, the reason being is that I wonder with all the fibres coated with spheres then the UV rays from sun might hit some sideways clinging spheres and bounce off each other like disco balls which reject the rays but bounce off each other towards the skin, can you view how much light gets through on a treated piece compared with a control piece? Also I gather that the wicking cooling is to do with convection heat drifting away like heat from a radiator and the UV emitting heat loss is like heat lamp which should be able to.still radiate out through the plastic sheet is that right!?..

[@juanluisclaure6485]

Best inventor slash youtuber of the world. Gracias por tanto saludos from Bo

[@Azyx90]

Note about the texture of the treated cotton. Pure cotton changes drastically when washed with too hight of a temperature. Cotton turns into more coarse and chalky feeling. It's easy to ruin t-shirts or sheets by accidentally washing them with too hot setting in the washing machine.

[@user255]

They are not ruined by it. Just wash them again with some softener.

[@aserta]

If there's one thing i love about NHL videos above all else, it's the approach. Find a topic, figure the basics, try something. Doesn't work? Not a problem. Find new solution, apply. Success. One of my OG subs and by far the one that makes me smile when i find an upload in the subs.

[@lostboytnt1]

There's been a growing trend for many creators to make longer videos lately, and most of them I'm just not interested in investing the time in watching them, you are an exception. If your videos are 30 seconds, or 2 hours, I'm still excited to watch every one. For those who may not have the interest and attention span as I do, maybe fill in some gaps with shorter simpler, and easier to produce (fluff?) content? While taking some of your valuable time, it may free up some of the burdens and allow you to put more time and effort into longer experiments.. Regardless. I love all you do, and often share your stuff with people I think would be interested!

[@gtjack9]

I do much prefer videos like this to be longer. I mostly watch 8-15 minute videos on average. A video like this I’d happily watch up to 30 mins at a time and happily soak up a series of videos, part 1, part 2, etc

[@Pottyde]

The coolest channel ever! Thanks, man, you're great!

[@mineton1293]

always a good day when NightHawkinLight uploads

[@PedroCarvalho-bk4yn]

This is one of the most interest projects I've seen.

[@wonjez3982]

I like how in chemistry roughing up a surface can be as easy as boiling it in some acid/alkaline solution. You just got to apply what you know and combine the steps. Epic results and procedure!

[@Grandwigg]

I for one quite enjoy these longer videos. I hope continued content in this format remains viable.

[@R-Tex.]

As always, amazing work! I just wanted to say that you should watermark your original footage (e.g., the shot of the coated fibers), like Steve Mould does.

[@htmagic]

NHL, very interesting video! Another trick from textile mills is to treat the cotton cloth in a weak caustic along with the warm water. The alkaline soda may do this too but the caustic swells the cotton fibers and allow it to accept the dye better. Wash the caustic before treating it with the solution. Good luck! Cheers!

[@Sonriah4145]

A infered heat lamp may be a good way to create consistent test conditions.

[@pastabreaker4385]

he has studio lights. Even those should put out enough light

[@bodugok]

I have found this entire series of experiments fascinating.

[@arnavjain7564]

Maybe the result is due to the thermal mass of just the cotton being too small which is why they can't retain their coldness or are easily heated? In comparison to the coating which looks like it is done on a tile or some wood piece... I'm not sure if i can get the point across with this but i hope it sort of makes sense?

[@TheFredmac]

I agree.

[@MrBrew4321]

One way to think about that is to imagine opening a freezer, everything in there is the same coldness. But if you pick up a loaf of bread in one hand and a bag of frozen peas in the other hand the peas are more likely to freeze your hand because of their thermal mass. Idk what the energy flows are in that experiment but it is certainly plausible that the cloth is like the bread and can't "retain its coldness" there I explained your thought I hope :D

[@Les__Mack]

Thanks for another great video. I always look forward to them.

[@h7opolo]

If you compare black shirts, one treated, one control, you will see the difference you expect because white fabric already has near maximum reflectivity. Give it a shot.

[@Zeusbeer]

if you treat a black shirt, it becomes white

[@h7opolo]

@@Zeusbeer true. I guess, the effect he needs is not reflectivity but thermal conductivity as well, not to mention the texture of the fabric would be unpleasant.

[@craftminerCZ]

I love how you explain every step so clearly I almost feel like I'm inventing this myself. Honestly an impressive teaching ability on top of the innovative mindset.

[@stormthrush37]

A lot of people forget that lots of failure and learning from them is a big part of later success! Sorry it didn't work out but it's all part of the process.

[@Altonfoust]

I can't wait to see it in use in the summer, I think you're current method could make a difference in the summer and even just a 2 degree difference is huge on a roof.

[@NickCombs]

I wonder if it might be possible to improve the durability of the painted surface with what you’ve learned here. If so, maybe it’s possible to create a sort of flexible material out of many tiny rigid surfaces that apply the paint in a way we know should work.

[@notsonominal]

Cool stuff, like litterally! Thanks for following up the paint video with this, super interesting!

[@asteliaz]

I'd be interested to see how the breathability of the fabric has changed with this process, because you mentioned the gaps got smaller. I feel like, as a t-shirt, any cooling that would've come from allowing air to pass through might off-set the theoretical additional radiative cooling. Might need an experiment where the cotton layer sits on top of a thermometer in different conditions, sunlight with wind vs sunlight with no wind.

[@topspeed250k5]

Good point...but allowing air to pass through the fabric only cools the skin by evaporating moisture from the surface of the skin. He discusses that the paper reports that the wicking of the treated fabric is enhanced, so evaporation and cooling is better by that secondary method. i.e. there may be less air directly getting through to the skin, but the moisture is being more effectively evaporated so more cooling occurs. Definitely worth testing. I guess to separate the evaporation factor from the radiation, that temperature test would have to be done in the dark.

[@Jehty_]

That shouldn't really be a concern for a practical application. Just use a fabric that has larger holes.

[@asteliaz]

@@Jehty_ fair point! But if my thought process holds any truth, and applying it to an existing t-shirt does reduce the breathability, it'd be good to know :)

[@TheFredmac]

I think that wicking is more important than air flow through the material when it comes to cooling. I have worked outside for a couple decades, but this is opinion not anything I have tested.

[@WeighedWilson]

I would think you'd went moisture evaporating on the skin to absorb heat from the skin instead of on the fabric to absorb heat from the fabric. Humans have the advantage of sweat cooling over animals with a heavy pelt because the sweat can rapidly evaporate in the air thereby pulling heat from the skin. A heavy pelt hinders airflow and therefore hinders evaporation.

[@JATmatic]

This an rare channel where the quality actually goes up.

[@id104335409]

The Arabs will make you a statue of pure gold my friend! Pursue this further!

[@GM-gh4dk]

I'd love you to continue the experiments on fabric, including synthetic fibers which are quite commonly used.

[@RumbleGroove-official]

cool how you are able to make this kind of stuff

[@Respectable_Username]

Love that you're publishing your null results too! We can't move forwards with science if we can't figure out what _doesn't_ work too ❤

[@fire17102]

Do you think maybe a ultrasonic cleaner could be used to stir bigger batches more effectively? Also, im sure with some more clever optimizing youll figure it out! Amazing work

[@linecraftman3907]

Doesn't it disintegrate stuff via cavitation?

[@TheFredmac]

Have you ever seen a non Newtonian fluid in a bass speaker? A cooking sheet over a couple of bass speakers might do what you're talking about.

[@scottrussell8465]

At 12:30, thank you, I was yelling at the screen that the agitation might have been enough! Thanks for satisfying that curiosity.

[@SHRUGGiExyz]

I'd be curious as to how well this type of coating would stand up to wear, if you'd need to reapply the coating often as the fibers rubbing together during regular wash cycles could kick off some of the pigment. When you mentioned coating polyester fibers in silica nanospheres it got me worried about the possible risks of silicosis assosiated with wearing something like that daily. It stands to reason any particles coating a fabric would be shed to some degree, and small silica particles coming off your tshirt into the air you'll be breathing seems like it may be a health concern. I'm no expert, though, maybe it'd be such low amounts it's under safe exposure levels even in manufaturing settings (ie cutting and sewing this type of fabric) I also wonder how much of the radiative cooling effect is gained by your original paint simply by having one flat outer surface doing the reflecting. IR being sent off the shirt only needs to be done on the outside, so apart from the sweat wicking you mentioned briefly, you might have better luck with a sample with only the outer layer coated. I'm imagining a similar process to your t shit bleaching, but by airbrushing part B onto a shirt presoaked in part A of the mix? Someone else also mentioned the geometry of cotton fibers simply being too microscopically fuzzy to really radiate heat effectively, so screenprinting patterns onto plain and treated shirts to give you an idea of how they differ. Plus, the ideal spots have to face the open sky anyways, so painting just the front, back, and shoulders would be the most efficient places to coat for the IR cooling effect. Get an IR transparent acrylic binder and paint yourself an IR cooling vest, and that would be a fantastic success!

[@SeegerG]

You're awesome. There are few with your skill and style. I haven't been thinking along such lines at all but you make it very inviting. I've always appreciated your good work man keep it up!

[@benkirkland5354]

Love this soooo much. Could it be that the air gaps between fibers are acting as an insulating barrier? Or could it be that since the fibers are cylindrical(ish), the infrared waves aren’t being directed outward as from a flat(ter) surface like the paint; they’re bouncing back and forth between them, thereby heating the air space between? Very interesting work as always!

[@giggiles8886]

2 Observations: 1) by enclosing the test area with the transparent cover you’re homogenizing the temperature of subjects within the enclosure 2) the nature of the fabric is air permeability which will equalize the temperature between the fabric and air molecules. The flat painted non-air-permeable painted surface would not tend to equalize.

[@PraxisPragma]

Who else also 👍the video before even watching it?

[@Wolf-yp2qk]

You could use thinner diameter cotton fibers to make a separate outer and inner shirt; which would maintain the total thickness of the shirt to aid in comfort while efficiently using material.

[@askbatguy]

im not even done with the video but i heard calcium carbonate is used as an antacid of sorts so ever have atummy ache just chew on your hat for a bit XD

[@RegebroRepairs]

This whole passive radiative cooling thing is revolutionary. Every single white building in a hot climate in the world should get painted with this.

[@jaogileme7082]

damn i'm literally trying the same type of research after i saw your first video but my aproach is coating the fabric instead of growing the spheres inside of them, things have been slow for me since i don't have a microscope but if i get somewhere interesting i'll try to reach out

[@Arcelux]

Ben you have one of the few channels that help the world in more ways than you know. Keep it up!

[@crestofhonor2349]

This is such cool stuff and seeing how the paint keeps stuff cool is fascinating

[@Pyrotechnicduck]

Just a few years later this man will find a cure to cancer, he just has the best and most creative ideas

[@andrewmagee1666]

I so wish you the best! You are most definitely worthy of turning your wealth of knowledge into wealth of finance! Love your content!

[@mrtavetski1859]

That was phenomenal! One of the best videos ive seen on KZbin in months. Thank you!

[@psychoDon525]

I don't know if someone else has commented, but one of the things that makes fabric so good at retaining heat is the air between each fibre. Someone smarter than me can explain WHY the air makes it warmer, but when you're using paint, there's hardly any air there, so heat transfer is a lot faster, so things like reflection rate would heavily influence the temperature. I'd suggest putting the treated/untreated pieces on something heavily insulated, something metallic, something cold, and something warm to try and see if maybe there's a potential difference that will show up with each of those. Obviously a big part of this is the reflection, so doing the experiment again in the summer could really help too. Anecdotally, I never really notice a difference in temperature based on what colour shirt I'm wearing, but hopefully your further experiments yield more fruitful results!

[@gooball2005]

Man, great video as usual! I love that you're not only exploring interesting topics that don't seem to be talked about all that much on youtube, but that you're also deliberately designing procedures that could be replicated in a garage without the need for specialised equipment. Respect!

[@Elric509]

As another commenter said, a more compact fabric would probably more effectively reflect light outward instead of in on itself, therefore i suggest using a kombucha/vinegar pelicle, or mother. It can be grown in any shape and size depending on the container it's grown in, not only that, but after rinsing and processing if you grew the microcrystals while it was soaked, then dried it so it shrinks, everything would be trapped within and compact. Like and respond if you think this idea has merit

[@recklessroges]

Thank you so much for posting this important milestone. I'm sure that this will have created many useful conversations.

[@justinbanks2380]

I love your community! The fact that you cover pretty in depth topics and yet still say something is over your head and reach out to your viewers (knowing you have a great community and knowledgeable) 😊

[@scott98390]

You sir, are an excellent scientist. Fantastic experimental process.

[@WayneEveland]

Thanks for being you. It’s people like you that make me proud to be a Michigander. Me and my young daughter love to watch your videos and it always sparks us to try more science experiments!

[@GeoffryGifari]

Pretty cool that experiments on your channel build on each other

[@W4iteFlame]

Parrot is a very good way to keep you watching while sponsor stuff is going. And parrot is cool. (Even without the coating)

[@JamesNewton]

Excellent work! Negative results are results. You've saved other a lot of time, if nothing else.

[@biteme9593]

more videos: not only because I'd welcome being able to watch more, but you should get more subs for being among the first people to make these kind of diy / experiment videos

[@rockapedra1130]

I really enjoyed this. The fact that it hasn't succeeded 100% yet is valuable in itself. This is real science. Perseverance is an often overlooked yet important factor in any form of real world R&D !

[@Simply_CH23]

"even in the failures we're learning things" is something modern science research needs to learn from. Very interesting project, and very well explained.

[@JacquesDV100]

I am really excited about this project, and just everything you do in general. Big fan

[@alphanaut14]

Will someone get this guy nominated for a MacArthur Fellowship? Ben, your constant genius in exploring and sharing new topics in practical science constantly blows me away. I'm a patron now, but that is nowhere near enough for you to properly explore these subjects.

[@kbee225]

I am a grad student at MSU and while I am not an expert in IR emissivity, this is my intuitive understanding of how resonance could help with tuning the emission spectrum. IR interaction unlike visible and UV photon interactions which happen in a subatomic level (change in the electron orbital) happens at a molecular level. IR photons (also microwave photons) cause molecular "motion". There are several modes to this, like rocking, twisting, turning, etc. (most if not all molecules will have more than one mode and hence will have more than one emission frequency, this is analogous to a spring - in a helical spring there is the transverse vibration: compression and expansion of spring, but there is also a bending frequency : when you support one end and flick the spring.) The natural frequency at which this happens depends on the properties of the molecule (much like the vibration of springs). But, since these molecules are surrounded by other molecules in their lattice positions, they can affect how well each molecule can vibrate. Especially in nanomaterials (where the total dimension of each nanoparticle is only one or two orders higher than a single molecule). So, these particles themselves can "vibrate" at a different natural frequency, which in turn can cause destructive interference (not always, but odds are that it will be suboptimal). We can "tune" the size of these nanoparticles so that their first resonant frequency is a discrete multiple of the molecules' natural frequency. If we did this, then IR interactions can happen easily and the IR emissivity will improve at this tuned frequency. I hope that makes sense.

[@Nighthawkinlight]

That's my intuitive understanding also but I'm not certain if it's correct. Something like the resonance of a sphere might "pluck" a molecule's resonance at a particular peak to stimulate more of its emission to occur at that frequency. Seems possible. Thanks for your input! I'll do tests with a bunch of sphere sizes soon and see if particular sizes seem to work better

[@kbee225]

@@Nighthawkinlight Always happy to help! Keep up the great work, I have to say I've been watching your videos for a few years now and when I retire I aspire to do backyard science like you do. For now, I'll have to stick to small electronics projects.

[@NeonPreservation]

Ben showing that the scientific method can provide interesting and useful data even with unexpected results. keep at it, good sir, we the Patrons are here for you! also, thanks for including Mose in the ads, Caiques are such goofballs!

[@expresscrayfish6094]

tent idea is actually great, could have the outer layer be a cooling layer exposed to the outside world then have an inner insulated layer that doesn't get as much sun exposure as its inside so doesnt heat up as much but still holds in heat and have windows or removable panels on the inner layer to control the temperature

[@EngChagas]

As a warm climate region native and resident, I would really like to see this experiment done again whenever you do have warmer weather. Maybe wait for the hottest season. Also I think it would be nice to keep these already treated in a somewhat controled storage, so if anything different was to be made in the upcoming experiment we could test them agains the (possibly) different process. Will try ro watch this channel more often, maybe even watch again something to give you more playtime as I cannot be a Patreon for "3rd world" monetary reasons. Everything I've ever watched here was interesting on both an educative and entertaining ways. Keep up the good work.

[@phlanxsmurf]

Love the full on experiments. Awesome video. Thanks!

[@donjud1]

I really appreciate your successes and failures. Failure isn't the right word. It's more like bumps in the road.

[@chinozerus667]

This was very interesting. Great video! For testing I'd suggest more stable conditions like a heat lamp with constant distance and settings to compare the results for various methods of application. Instead of stirring you could have the solution flow over the fabric and have the fabric stretched on a frame to provide more surface area for crystallisation. Can't wait to see more of this

[@Sirzerty]

Thanks for doing the ad with your parrot all the time. It's my wife's favorite part! I've been looking into a lot of what CaCO3 can do thanks to you, and managed to save a lot of money this year by using hydrated lime to neutralize acid in my wood boiler vs using the manufacturer's propertiery unlabled powder that costs $30 a tub. Plus I'm planning on making mortar (lime putty based) comparing eggshells, hydrated lime, and high calcium lime (heating and slaking eggshells & hi cal lime, just salking hydrated lime)...and building the base of a greenhouse and small goat shed with them.

[@TheAzachiel]

You're legend! This is absolutely awesome. I nearly sure that plastic layer prevents IR from escaping to outer space. I think it works as intended.

[@ThistlesGarden]

Great video, nice to see all the work you did to give the experiment the best shot you could.

[@jaspurr7467]

I love the passive cooling series!

[@AndreaDingbatt]

This is Awesome!!❤ ~and I have to say that it's a Fantastic Solution, for the Equines that Work in Hotter Countries, ~ it would make their working lives so Much Better!! ❤ Hoping to hear when you're ready with a Positive experiment!!❤ All Experiments are relevant!!❤😊

[@caffeinato]

A random note perhaps of use, when you mentioned figuring out a method to selectively deposit these microspheres onto one side of the fabric only. Some sort of spray system might work, but adhesion to the fibers would definitely be poor/too easily lost, so growing the spheres directly onto the fabric as you've done appears to be the way. If you had a fabric with a very tight weave, such that bulk movement of the liquid through it is quite limited, if you used the fabric as a semi-permeable barrier between the two reactant solutions, perhaps you could soak the fabric with one of the solutions, get the spheres to grow on the contact side, in the process filling gaps and limiting further flow across. Sonication could help tune how much mixing happens over what distance. Could try soaking the fabric in the more dense solution, floating the fabric evenly on the surface (one layer only), then very carefully pouring (or spraying) the less dense solution overtop, with the overall goal of making the interface between solutions as thin as possible and hopefully localized to one side. Watching this series has been really incredible, and I'm sure I don't need to repeat what everyone's saying, that these videos are absolutely excellent examples of citizen science, and your communication skills for these topics are really a cut above.