Why white things are white

Almost all white things are white because of scattering. You can do really cool things by playing with refractive index to dial up or down the amount of scattering, you can even make things disappear. It's how a Buddha Board works!

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[yaqxs]

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.

[jans]

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

[JackLe]

Is the uncensored version a Patreon exclusive?

[proudtoberainy]

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!

[davidioanhedges]

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 ...

[McPhysX]

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.

[plinkage]

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

[matthewpetty]

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.

[mduvigneaud]

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.

[robertwilliams]

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

[peterryrfeldt]

1:00 amen brother
tau is the true circle constant

[patromo]

"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

[PK-hsup]

Hi Steve, I would <i>guess</i> 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.

[deesync]

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!

[AlRoderick]

If you've ever watched hard candy making, like the stuff made by Greg from Lofty Pursuits here on YouTube (okay it's actually made at his shop in Tallahassee Florida but he puts the videos on YouTube) 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.

[thesoupinor]

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

[thenamethatwasntaken]

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

[ChubbiestLamb]

1:03 "the superficial explanation"

Superficial - existing or occurring at or on the surface

Very appropriate wording there, Steve...

[shadyganem]

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

[felipegonzalezlelong]

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