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There is a technique in animal and organ preparation called Spalteholz preparation. By matching the refracting index of the conservation fluid and the outer layer of the object the object becomes translucent. So you can study the inner parts of your object without a section. It's called after its inventor Werner Spalteholz and I don't know if it's known outside Germany.

A patent for one of the types of hydrochromic coatings lists the active water activated hydrochromic materials as : sodium aluminum silicate, alumina trihydrate, micronized amorphous silica gel ...

6:30 We actually know very well why! A *Colloïd* is simply a name given to any object that has a size from 1nm to 1µm. When you shake water and oil together you are creating droplet of oils that are colloïds! Colloïds are unstable by nature because of surface tension. Oil droplets will naturally do two things: 1) If they are less dense than water, *rise up to the surface* 2) *Merge into bigger droplets* , because bigger droplets are more stable in regards to surface tension For your colloïd suspension to be stable you therefore have to counteract both effects. 1) is easy. A particular property of colloïds is that they are so *small* , that natural random movement that all molecules have become non negligible. Therefore if the speed at which they rise up to the surface due to archimedes is lower or equal to the speed of their random movement, they won't rise and will fill the whole volume, like a molecule would. This is mainly dependent on their size, the *smaller* they are, the more they *diffuse* and the less they rise. 2) Is harder but essential. Surface tension will merge any colloid suspension, unless you have particular molecules that stabilize the suspension. Which is the case in your alcohol! *Proteins* , soaps, surfactants,... any molecule that has a *hydrophilic and a lipophilic* part will place themselves at the *boudaries* of these tiny droplets, *reduce surface tension* , and make the droplets repel each other, therefore they will stay small and never merge. It is a well studied phenomenon, especially in *biology and pharmacology* , where you often want *oily molecules to be suspended in a water solution* for delivery, and you don't want your medicine to divide into a fine layer of high concentrated oily molecules and a deep layer of useless water.

"titanium white" makes alot more sense now as a color name.

We're a company that makes a hydrophobic coating designed to create art that appears when it rains. Our process relies on the fact that concrete gets darker when it gets wet. I've dug into why this happens several times but your video provided a more clear explanation than I've been able to find before, thank you! Interestingly, hydrochromic paints list silica as an active ingredient, which is also an ingredient in our hydrophobic coating. It's wild that silica can act as a white-to-transparent ingredient as well as a hydrophobic ingredient. If you ever made a video about the stunningly varied applications of silica, I'd be extremely interested to see it!

"Ooh! That's why!" - Me in every Steve's video

I bought a similar 'Buddha' board in China for practising writing Chinese characters using a wet brush. The top coating of this one is actually a thin layer of fabric (assuming cotton) over a black rubbery plastic to create the effect.

1:00 amen brother tau is the true circle constant

8:16 that face

The blue shower gel reminds me of how all mirrors are a tiny bit green, but you can only notice it from a really extreme angle

I used to work for a paint manufacturing company a while back and the TiO2 slurry was one of the most significant ingredients in the paints.

If you've ever watched hard candy making, like the stuff made by Greg from Lofty Pursuits here on UKposts (okay it's actually made at his shop in Tallahassee Florida but he puts the videos on UKposts) he makes white hard candy by pulling the molten candy on his stretching hook or his taffy pulling machine to aerate it and put a million tiny air bubbles in it.

That's so interesting. I learn so much from this guy. He is also the right amount of funny.

"Got to be handy with the steel if you know what I mean to earn your keep" I just let out a honk of a laugh

1:34 the microscope disappeared!😜 I love the sticky tape on a frosted glass trick...I can't wait to try it out! 10:10 the microscope appears!...11:13 disappeared again.

Aha! There's a name for the nanoemulsion formed by diluting alcoholic solutions: the ouzo effect. It has its own wikipedia article. ◡̈

Speaking about presentations... It's just amazing how far you've come to make explaning such things look so easy... You're an idol Steve! Keep up the good work!

One test you can run on the theory is to foam up the shave gel and then form it into a long line of foam and then illuminate the foam from the far end, opposite the camera. The light it sees should be that which had to pass through a lot of the gel (hence, blue). You may need to put mirrors along the sides of the foam to redirect all of the scattered light back into the foam (or else you might see very little light making it all the way through the foam)

0:45 Tau Nice

2:31 HEY LOOK!! HEXAGONS!!!! 😁

In metal polishing, we sometimes aim for the opposite of this effect. A "black" polished surface is so smooth that it no longer scatters any appreciable amount of light, acting like an almost perfect first-surface mirror. From certain angles it will appear completely black, because all of the incident light is reflected away from the viewer. It's most often seen on components in high-end mechanical watches, but we use the technique a lot for injection moulds for plastic optical components.

Here after Hexagons are the Bestagons and I couldn't stop seeing 120° angles in the bubble cross-section! Super cool to see

Hi Steve, I would guess that this hydrochromic image is just coated with silica gel or something like that. Maybe you want to test this: Take an image, apply spray glue on it and dust some silica powder over it. Maybe it is something with an RI even closer to water instead of silica, but ... just a guess.

Eyes: What color is this? Brain: All of them.

What an easy man to listen to. Great information on curious subjects delivered in a very pleasant way. Top stuff! This gentleman has the hallmarks of a great educator.

I think my favorite example bubbles scattering light is with candy. To make white hard candy you take molten sugar and folder over itself continuously, essentially folding air bubbles into the candy which lightens the color. (The same works for turning a- say- dark blue colored candy into a light blue candy.)

For being a wave, the photon particle has a very physical way of interacting with the environment

That phenomenon of some alcoholic beverages turning white/opaque has been bugging me for half a year now. Thank you for finally clearing that up. (no pun intended)

*hits blunt Whoah dude. So is the shower gel still blue in the bottle? Since no light can get to it?

LOVED the blurring of the wet shirt. 😂

10:47 People who watch Tom Scott might be aware of this. 😂

Hot thumbnail

That Regulators reference took me a while, but was much appreciated. Great video, as always. Got me extra hyped for Unnecessary Detail season 2 as well.

That was really fascinating. Thank you 😊

11:08 "You gotta be handy with the steel, if you know what I mean. Earn your keep." REGULATORS, MOUNT UP!

"Oh my god Karen, you can't just ask people why they're white"

"I've got Titanium Dioxid on my walls!" sounds way better than "My walls are white."

I love how you used a beaker for the t-shirt demo, that way everyone knows its not just crass entertainment...ITS SCIENCE!

Me: "Dad, why is shower gel blue?" Dad: "For the last time, it's because of Rayle... wait, what?"

Hey Steve, you ve done an amazing video and clear explanation to the subject. Thanks for that. I'd love to request from you to put captions to the videos you share. Even though your accent is so clear, I sometimes can't understand because of lack of English I have. It'd be great if you consider it for your videos. Nevertheless, it's amazing to watch and learn from you. Thanks a lot!

Thank you for this odd but very interesting observation. I’ve been kicking around an idea for a project at work and I now wonder if this could be a step towards a solution

It's very thoughtful of Steve to warn those of us who know the real and 100% correct pronunciation of GIF.

Loving the Nate Dogg/Warren G reference... Regulators! Mount up...

But the question is, where did that microscope thing in the background went at around 01:34?!

I really like how you don’t avoid answering the questions that may arise from the concepts you present

This was a great explanation on transparency of the materials and white color apparience on matters, better than other explanations like electrons jumpimg to different orbitals. Thank you for all.

In the foam, the amount of light that reaches the inside of the material is lower because there are so many surfaces that reflect light before enough thickness of the material is encountered. Less light reaching the gel means less red & green light is absorbed. Also, the total brightness reaching the eye is higher, so the remaining blue photons are more diluted

This was cool but can you explain glue? it's white when it's wet but gets transparent when it dries, how?

Pernod or pastis in general does eventually become clear. Just like any emulsion, eventually it separates into two layers. That said in pernod there is only little "oil", these insoluble particules might form micelles or other arrangements that stabilise the emulsion form

I was just talking about something along these lines with a friend last Sunday morning. Glad I subd, gotta keep the gears turning up top.

Me, after I looked at the thumbnail: Ah yes, many people's favorite album... "DAMP."

Oh god the thumbnail! :)

I've always wondered why adding white paint to other colors made it opaque, and I feel like this explains it pretty well!

Fantastic explanation, very thorough and brief at the same time.

"He does pronounce it 'jif', soo..." :)))

5:10 where do the people go? When will they come back? Am I the only one distracted by them?

Excellent Regulate reference, very smooth!

Great lighting in this Steve!

8:16 What a face

I am going to have to try these myself.

1:03 "the superficial explanation" Superficial - existing or occurring at or on the surface Very appropriate wording there, Steve...

1:30 Why does that thing in the background disapear?

It won't work if the frosted part is on your cube neighbors side :(

I guess the lipids in the perno (or however is called) have some kind of polar molecules that eventually make a little ball around the insoluble lipids so that it separates the lipids from the water. A similar thing happens in your blood to transport cholesterol and fatty acids. (They are called ldl hdl and quilomicrons, all of them being lipoptroteins) i dont know this for sure but it makes sense for me. Edit: turns out perno is not aromatic oil (as i assumed) so probably this is not the reason, the video, specially comparing it to the emulsion of oil in water made me confused

Thanks for this info! I'll be sure to remember to bring all my tape when visiting the changing rooms that have the frosted doors

Steve clickbaited and he delivered. He is truly a hero.

Honey I am watching this wet t-shirt contests for research purposes I swear!

"Regulators, mount up"

My man you find the most unique things to study! There are some seriously enlightening things hidden in the world where nobody else is looking. I wonder how you actually get places ignoring the sidewalk to travel through all the cracks

Fascinating stuff! Always love some *Light* learning! No, seriously, anything to do with light is great.

8:15 😍 The goods you came to see. Kinda.

Really neat, thank you! Any ideas why some plastics turn white as you deform them? (i.e. plastically deform usually)

I am glad someone asked this question

Sir, once in my life, I wanna meet u. U r genius! U having knowledge mostly every field. And I also loves to learn new things.

7:10 sounds a bit dodgy if you had frosted glass showers

Now explain Elmer's glue. White when wet, dries clear. 🤔

6:20 I did a little controlled experiment: turns out ethanol helps stabilise oil in small droplet in water, turning the water cloudy. Maybe the ethanol molecules act like amphiphiles ("ethan" part towards the oil, "ol" part towards the water). A bit like soap dispersing the oil throughout the water. Maybe it prevents coalescing of the oil because the ethanol layer needs energy to be broken.

Great Video! It is great to see that such simple seeming things can have such a rich and interesting explanation. One point however, where I had the feeling that you were rushing over, is the fact why the scattering is the same for all wavelengths. Just the fact of a rough/non-smooth surface and that, for the bubbles, you have refraction from inside the foam does not seem to me as enough of an explanation as to why all frequencies are scattered equally. Could you point me to some literature/site which explains that in more detail?

Ahhhh! I tried replicating what he was doing and got a bunch of photons in my eyes.

I hadn't heard of Buddha Board before, but when you described it, my mind immediately jumped to frosted glass. I own a frosted glass chess set (half the squares/pieces are clear glass, half are frosted), and after I had used it a fair amount I found the glass had a lot of fingerprints on it and I wanted to clean it. I got a damp cloth and wiped it down, and much to my surprise all of the squares disappeared. Sure enough as it dried, the frosting came right back.

Absolutely the best pronunciation of skl.sh I've ever heard. Five stars.

I appreciate the correct use of the plural of index.

You should try adding Pernod to heavy water, Deuterium, and see if it separates out then

Apparently, all sunscreen lotions I've checked have Titanium Dioxide in their composition... Is this scattering responsible for their UV protection?

Woah, a wild pebble time steel! I don't remember the last time I saw another one of those, nice!

Those "colorful when wet" umbrellas are my favourite use of hydrochromic paint.

Typical, Steve Mould perceives the first three number of 2 × Pi as art xD

so paint your house colours to annoy your neighbours, then cover it in the same paint as the board. and only annoy them when it rains

those were some solid sksh recommendations also, awesome video

This takes me back to my year 12 high school physics project. I asked myself the same question about white foam on a freshly poured glass of soft drink and came up with this as my topic. Good to hear it again and confirm my presentation.

man for once id like to see the massive bong hit i assume Steve does before starting his videos..... i can imagine all that white smoke!

Steve: _Pernod_ My ear: *Porno?*

During all the years, when watching wet t-shirt contests, I never came to think WHY the shirts turn translucent... 😁

Finally someone explained how wet t-shirt contests work! XD Thank physics for this great property of fabric.

You’re the new Vsauce. There I said it.

"He does pronounce it JIF," nope. Can't watch that.

Hi Steve, A really interesting video... I think I may get myself a Buddha Board... thanks for sharing. Take care Paul,,

The glare on the liquid was an amazing demonstration. I instantly understood at that point