If this takes over and is used everywhere, in 50 years, will people become nostalgic over titanium dioxide white? Will the titanium industry be supported by the few remaining vintage white paint manufacturers? \s
Whitest paint is now thin enough to coat cars and planes
31–40 of 73 posts
Re: Whitest paint is now thin enough to coat cars and planes
#32Very cool, but im skeptical about cost
With less than 300 grams of paint per square meter and a pigment made from cheap ingredients, it is unlikely to be more expensive than titanium white, but obviously this will be true only if it will be produced in large enough quantities.
Re: Whitest paint is now thin enough to coat cars and planes
#33Earlier quoted context omitted.
A simple way to verify this is to observe that common mirrors also tend to be green, showing that the other colors are absorbed more by the mirror. If you face two mirrors towards each other you will see a lot of green. edit: here's an example: https://i.imgur.com/Ar80FYZ.jpeg
The common mirrors have the metal on the back side, so their reflectivity is diminished by the absorption in the glass. The better mirrors, which are used e.g. in telescopes and some other optical instruments, have the metal on the front side, but that limits the metal choice to aluminum, because silver is tarnished quickly by the sulfur compounds present in the air.
so why don't common mirrors just use aluminum? It's already cheaper than silver, right?
Re: Whitest paint is now thin enough to coat cars and planes
#34Re >> "with an ability to reflect around 98% of incoming sunlight" Seems like a mirror would reflect even more light. Now, obviously we don't want to make the exteriors of our buildings and cars a mirror! . but it made me wonder: What's the difference between a really really really white paint that reflects 98%+ light, vs. a reflective surface? Is it that the white paint reflects the light, but in a "scrambled" form,…
Nope. Silver reflectivity is about 95%, aluminum reflectivity is about 90%. So the best metallic mirrors are worse than the best white paints, even if they can be better than the frequently used white paints based on titanium white (89.5% reflectivity). Total internal reflection might be closer to 100%, but that cannot be used for the light that comes from the air on the surface of a mirror.
You can have dielectric coatings on a mirror that increase the reflectivity to >99.9% (and over a wide range of wavelengths). You can of course get a lot more 9's if you only care about a narrow band.
https://materion.com/products/precision-optics/application-f...
Re: Whitest paint is now thin enough to coat cars and planes
#35Re: Whitest paint is now thin enough to coat cars and planes
#36Earlier quoted context omitted.
The common mirrors have the metal on the back side, so their reflectivity is diminished by the absorption in the glass. The better mirrors, which are used e.g. in telescopes and some other optical instruments, have the metal on the front side, but that limits the metal choice to aluminum, because silver is tarnished quickly by the sulfur compounds present in the air.
so why don't common mirrors just use aluminum? It's already cheaper than silver, right?
The common mirrors have been using aluminum for a long time.
I do not know when aluminum has replaced silver, but it was probably not a long time after WW2.
The silver mirrors had the advantage that the metal could be easily deposited from a water solution, anyone could make silver mirrors at home, if desired.
The aluminum mirrors use a vacuum deposition process, which requires very expensive equipment, but the cost per mirror is much less.
Re: Whitest paint is now thin enough to coat cars and planes
#37Earlier quoted context omitted.
so why don't common mirrors just use aluminum? It's already cheaper than silver, right?
The common mirrors have been using aluminum for a long time. I do not know when aluminum has replaced silver, but it was probably not a long time after WW2. The silver mirrors had the advantage that the metal could be easily deposited from a water solution, anyone could make silver mirrors at home, if desired. The aluminum mirrors use a vacuum deposition process, which requires very expensive equipment, but the cost…
Ah. I misunderstood your earlier comment. Thanks!
Re: Whitest paint is now thin enough to coat cars and planes
#38Re >> "with an ability to reflect around 98% of incoming sunlight" Seems like a mirror would reflect even more light. Now, obviously we don't want to make the exteriors of our buildings and cars a mirror! . but it made me wonder: What's the difference between a really really really white paint that reflects 98%+ light, vs. a reflective surface? Is it that the white paint reflects the light, but in a "scrambled" form,…
To make things simple, yes, that's is. White "scrambles" the light, the correct term is "diffuses" but that's the idea.
Maybe quantum physicists will disagree but the difference between a mirror and a white surface is that a mirror is perfectly flat and therefore will reflect light at always the same angle. It may absorb some of it, or even most of it (black mirror!) but what it reflects, it will do it always the same way.
A white painted surface can be thought as a surface covered in tiny mirrors, all pointed in a different direction, and depending on which tiny mirror a ray of light will hit, it will be reflected in a different direction. With large pieces, like with a broken mirror, you will still see (as you said) scrambled images. But because the pieces are so tiny, you won't be able to make out an image and you will only see white. A glass pane can look like a mirror, but reduce it to a powder and it becomes white. It has nothing to do with absorption, you can have a 1% reflective mirror, and 100% reflective diffuse white.
The way the "tiny mirrors" that make up the white paint are oriented give out its general look. Have them oriented mostly with the surface and you get a glossy finish, have them randomly oriented in many directions and you get a matte finish (this is called specular reflection btw).
I've seen mirrors be called "smart white", it is white because it reflects most light in most wavelengths, and it is smart because it keeps the rays of light oriented.
Re: Whitest paint is now thin enough to coat cars and planes
#39Couldn’t this be revolutionary for spacecraft?
Also would it make a better solar sail?
Re: Whitest paint is now thin enough to coat cars and planes
#40I know nothing about this sort of stuff, but if this were applied to cars, would there be an increased risk of temporarily blinding other drivers on a sunny day?
It reflects something like 98% of light instead of 90%, so the actual increase in reflected light isn't that big.
Flat scattering surfaces are never blinding. The problem is with specular reflections off of shiny surfaces. Even though a shiny surface may only reflect a small fraction of incident light, it's all pointing in one direction which can dazzle observers.