How white can white paint get?
gizmodo.com
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A temperament that I share with everyone on HN is a suspicion of convention. So many common practices are dumb that it's hard to see each one coming in advance. One is always on edge waiting for the next shoe to drop. I'm supposed to spend days clearing my apartment, so the bottom rung of the construction trades can come in using paint that only lasts four years, dabbing hanging peels back in place with their brushes? Why did I actually have to go through this once to see this is the poster child for "stupid"?
I've also never understood the fashion choice of "off white". Titanium white is brighter, a better lit room day or night. It can become a color mirror, where a corner looks red because a red object is nearby.
For anyone tempted to try this, the student grades have less pigment, and the most expensive brands have the most pigment. It would also appear in an art supply store that there's only one kind of primer, and mediums vary only by gloss. Going to the manufacturer's sites, there are variations intended to survive the outside wall of a building. One could probably wind up someone on a phone call, and get excellent advice on which products to use. On the other hand, I used what I found at Pearl Paint in NYC, and it held up fine.
Personally, if it's a room I'm going to be relaxing in (bedroom, living room, etc.) as opposed to a work room, I strongly prefer an off-white over a bright white. It's more muted and relaxing.
For instance, bright white paint + 2800k lamps may vibe similar to eggshell + 3200k lamps.
But adjusting the wall color through lighting is more complex than just having the walls be painted the shade you want.
There's no man made source that exactly replicates the sun.
I'm certainly not saying that anyone else is wrong for having tastes that differ from mine.
Stark white in a brightly lit room can be overwhelming. Sure you could dim the whole room, but now you've dimmed everything. For something like a gathering room, where a person may want to be reading, such a solution doesn't work.
And I'm not using 'soft' white bulbs that make everyone look jaundiced to hide the wall color.
Much easier all around to go offwhite(or anything but white) on the walls, using neutral 3kish bulbs to your preferred brightness.
Yes, using paint color to control room light is easier. It’s just less flexible. If you just want to throw a bunch of furniture and lights in, paint color is simpler.
If you want the flexibility for the room to present as daylight white sometimes and cozy amber evenings at other times, it takes more work in lighting and for furniture choices, and neutral white walls increase flexibility.
Neither answer is “better” in some objective sense. It’s just a simplicity vs power choice.
Very worth the extra expense!
Get bulbs with a higher color rendering index. I made the mistake of getting warm white LED bulbs from the local hardware store. Those things are positively yellow. The warm LED bulbs from IKEA on the other hand aren't any bluer, but they keep white looking like white.
Ended up on the sketchily named "energetic" brand from Amazon. 3000k, and claims to be CRI80+. Unsure which of those is more important, but I finally found my goldilocks bulb.
Sheen has almost no effect on LRV and thus how much light reflected from a fixture is bounced in the room.
While it is true that matte finishes have particles that are diffusing light so that the surface does not look as shiny, no sheen is actually specular enough to reflect a meaningful amount of light.
Especially compared to the color
(This is crazy for people to accept at first but it is in fact correct and you can prove it to yourself if you want)
In other words, artist paint and house paint use the same base pigment. Almost all commercially available "white" housepaints are based on titanium dioxide pigment. The special thing about artist paint is the extraordinarily high concentration of pigment.
I miss Pearl Paint. It was strangely fun to go up those stairs.
[in case you're curious https://www.artistsnetwork.com/magazine/pearl-paint/]
I was shocked to find out it is closed (fairly recently actually). Last I felt this way in newyork was when they closed the art cinema close to lincoln center back in the day. (Don't remember the name now.)
In the Mediterranean (at least, probably many other areas) this has been done for thousands of years by painting the houses white to keep the heat out as much as possible, as well as a variety of other techniques like smart air management. So I think "as far as the 70s" is fairly misleading, it should be more like "for thousands of years...".
Easy to apply, long-lasting, biodegradable, and (from the linked article) it "produces a unique surface glow due to the double refraction of calcite crystals."
Mediterraneans: get out of here
Edit: how to make lime/limestone in a low-tech way from Primitive Technology:
As far as the 70s refers to efforts to create whiter and more reflective paint.
Yours appears to me to be a view that is very strange not to extend back beyond the 1970s.
We know how people work, in societies, at this broad-stroke level. This level of pedantry gets us nowhere.
No it isn't. Mine is an asumption that "white" was just a color before we understood what light is, which doesn't happen until centuries later. Searching for ways to produce "the whitest paint" is unrealisric given that we are talking about objects that reflect invisible light here. Not "white" the color. And there is also a difference between using something and creating something for that purpose. Saying that scientists are now searching for the whitest paint does not imply that nobody was using white paint before.
>This level of pedantry gets us nowhere.
It gets us to the question of whether ancient societies looked for ways to produce paint that reflect more light in order to prevent heat absoption which is what has been hapening since at least 1970.
Light and color weren't scientific concepts until basically Newton. And then you needed significant advances in chemistry, optics etc. to even begin measuring and thinking about such mundane things as application of color to house exteriors.
Yet, any child knows that stepping on black asphalt burns your feet. The conclusion that "less dark means less heat" is trivial. I think it's odd that people think so little of the members past civilizations, with brains no different than ours.
Having stored some old closet doors on the porch near a small urban road for a few months, this was my first thought. The grime that accumulated from exhaust was incredible. (There were leaf blowers running across the way a couple times a week, so I'm guessing those were the main culprit.)
Things turn dingy in the city remarkably fast. Cleaner cars and elimination of two-stroke engines will help, but for now I think that for most exterior uses, "resists smog" will be more important than "starts out very white" unless you clean it frequently and thoroughly.
The thing I am pondering: if the objective is to reflect as much as possible sunlight shouldn't the solution be more like a... mirror than a white paint? According to wikipedia a very complex dielectric mirror can reflect up to 99.999% of the light incident upon it while simple mirrors may reflect 99.9% of the light.
Cost and practicality will significantly lower these figures but there is still a gap versus the current 98.1% white paint record. I recall seeing various gold tinted mirrors covering buildings but they seem out of fashion.
That actually makes the problem much worse. Normally with a few flat reflective surfaces around, you'll catch occasional reflections of sunlight and flinch away from them. But with a very reflective rough surface, you catch reflections of sunlight every direction you look and it will burn your eyes.
This is how "snow blindness" works. Fresh white snow is very reflective and very rough, on a bright day with fresh snow, you catch sunlight reflections every direction you look and if you don't limit your exposure, you can get painful UV burns on your eyeballs. Sunglasses or traditional snow goggles become essential if you're outside for long in these sort of conditions: https://en.wikipedia.org/wiki/Snow_goggles
It can also happen when you're on the water on a bright day, depending on the state of the waves. At somewhere around sea state 1 or 2, you start catching sunlight reflections off waves every direction you look and if you don't have sunglasses you'll be in for a shitty time. When it happened to me, it felt like having glass powder trapped under my eyelids.
the more directed the light source the more damaging for retinas (all other things being equal). that is why you have prohibitions on powerful laser pointers.
what you are describing is the effect where diffuse reflections can integrate over time (since the impact is not immediately felt) and cause damage this way
Yes certainly, but in the real world the human blink reflex means that all other things aren't equal. If you walk past a shiny glass building, you might catch a reflection of sunlight but only for a brief instant. Turn another direction and you'll see another shiny building, but you probably won't get a sunlight reflection off that shiny building because the angles are different and the sunlight is being reflected somewhere else.
You can walk around a mirrored city all day and your eyes will be fine. But when you're surrounded by diffuse reflectors, now can't turn away from that reflected light. A city of pure white reflective buildings would be likely be quite painful on a bright day.
You skipped the "but only for a narrow range of wavelengths, ranging from a bandwidth of only 10 nm to as wide as 100 nm" part
> while simple mirrors may reflect 99.9% of the light.
Simple as in "enhanced silver mirror" ? Not that simple https://www.thorlabs.com/newgrouppage9.cfm?objectgroup_id=81...
The regular silver mirror part is:
> Silver is expensive, soft, and quickly tarnishes, but has the highest reflectivity in the visual to near-infrared of any metal. Silver can reflect up to 98 or 99%
Curious ; what wavelengths 'carry' the most heat? or capable of carrying the most heat?
And what reflective material/color is best at reflecting most heat?
I ask because I used to have a friend who was a physicist at Intel and he couldnt tell me what heat actually was...
Do we have an answer to this?
Most of heating is from infrared iirc
What property of matter is 'heat'
That's why the concept of a black body, an idealized thing that radiates a continuous spectrum is used to reason about heat transfer from radiation.
Bottom line, there's no single wavelength that carries most heat, it depends on how the heat is generated, what the emissivity of the generating body is and what the absorption of the receiving surface is.
How much is geometry vs material science?
We know that anachoic chambers have pyramid-ic structures of foam.
So I propose the most stealthy paint would be tiny pyramids of aero-graphene in a spray with a carbon based paint, such that the pyrs absorb bot heat and sound and radio waves.
Look up Plank's Law. Its an equation for black body radiation (like, effectively, the Sun). That'll tell you how much heat the Sun radiates at any given wavelength.
That's not the same spectrum as falls on your house, the atmosphere has absorbed or scattered some of it. But the distribution that falls on your house is well known.
A dielectric mirror is fairly narrow band, compared to this distribution. A dielectric mirror might work well for a factor of two bandwidth, but solar radiation is significant for about a factor of ten.
Also dielectric mirrors are: 1. Hard to design 2. Expensive relative to paint 3. Rather fragile compared to paint.
Point 3 is important. You can't just pressure wash your siding to clean it without stripping the dielectric mirror. But if you don't clean your siding the mirrors can't reflect the sunlight!
As to heat, heat is technically thermal energy transferred from system A to system B by a temperature difference. It has units Joules. In practice it also refers to the thermal energy a system has.
Thermal energy is the kinetic energy a material's atoms and molecules have because they're vibrating about.
Finally, these are hard questions because they start to hit upon the fundamental definitions in physics and everyday misuse of definitions by physicists themselves. Furthermore laymen have used the word "heart" far before physicists stole the term to refer to something similar but technicals in their field. They did the same thing with the words mass and weight when we needed to distinguish between the force and the mass in the 17th century (its perfectly Ok to say "weight" to refer to mass in most situations including most engineering, chemistry and physics applications)
What property of matter is 'heat'
E.g., an object's atoms are vibrating a lot, and you touch it, and that vibration spreads to your atoms, so you say you've noticed "heat" in that object. Or the vibrations are emitting radiation (like infrared light) to you, and the radiation begins vibrating your atoms, so you might say "heat is coming off of that object".
>Heat is energy in transfer to or from a thermodynamic system, by a mechanism that involves the microscopic atomic modes of motion or the corresponding macroscopic properties.
>In the kinetic theory, heat is explained in terms of the microscopic motions and interactions of constituent particles, such as electrons, atoms, and molecules.[57] The immediate meaning of the kinetic energy of the constituent particles is not as heat. It is as a component of internal energy. In microscopic terms, heat is a transfer quantity, and is described by a transport theory, not as steadily localized kinetic energy of particles. Heat transfer arises from temperature gradients or differences, through the diffuse exchange of microscopic kinetic and potential particle energy, by particle collisions and other interactions.[0]
[0]visual proof: https://i.imgur.com/Ar80FYZ.jpg
It would be blinding and burning and visually be confusing.
White paint is at least cheap.
Besides optimizing reflective performance versus monetary cost one would have to also take into account the full product lifecycle (dependence on fossil fuel, recyclability etc). I know what "a fresh lick of paint" means, no idea what "a fresh mirror coating" would look like :-)
But overall a fascinating topic which like the converse (insulation of buildings in cold climates) has a major footprint
Graphite and its compounds are important black dyes.
To go a step further: Vantablack, like most other carbon nanostructures, is functionally graphitic (sp2 bonding). And it's the blackest pigment known.
I wonder if the boundaries of hBN can be pushed in the same manner. Perhaps hBN nanostructures can make for even whiter pigments? It'll be interesting to find out.
As an aside, I had once heard that beryllium oxide is the whitest known pigment, but it's so rare and toxic that it can never leave the lab under any reasonable circumstances.
Don't let industry know about it, they'll be putting it in our toothpaste!
https://culturehustle.com/products/black-3-0-the-worlds-blac...
And the blackest (non-acrylic) paint is Vantablack, the carbon-nanotube-based paint that is infamously only available to Anish Kapoor.
A reminder that you’re allowed to care about whatever you want.
Of course, there's plenty of research[1] showing women are better at color discrimination than men.
0. https://ec.europa.eu/research-and-innovation/en/horizon-maga...
1. https://pubmed.ncbi.nlm.nih.gov/21675035/#:~:text=Color%20wi....
Maybe gutting art programs in American public schools was a bad idea.
> Abramov explained in a statement these elements of vision are linked to specific sets of thalamic neurons in the brain's primary visual cortex. The development of these neurons is controlled by male sex hormones called androgens when the embryo is developing into a fetus.
Is this something you (or people you're familiar with) believe? Never encountered this norm before.
As an architect, I can confirm that there are many men who know the difference between cream/milk/eggshell!
So any particular man may see color as well as any particular woman, but if you had to pick one person at random to save the world in the galactic color identification game show, you’d best pick a woman.
Often what many think of as white is white mixed with blue. This is super evident after properly calibrating the white point of a (good) TV. Most casual viewers will say that the whites are now yellow/orange but in reality they are just used to always looking at white with a lot of blue mixed in.
I've had similar experience with a interior designer friend of mine who told me my new white walls were not white but cream. I have a spectrophotometer that pretty clearly said that my walls were closer to white then his walls that he insisted were proper white (they were white mixed with blue)
Most content is mastered for this 6500K as that is what the D65 standard is and the tv/film standards like Rec709 and Rec2020 use D65.
"White" is tricky, because it's dependent on color temperature of the light which is illuminating the given surface. If someone is used to viewing white objects under daylight, but you're calibrating their TV to match the color temperature of their indoor environment (which proper calibration should do), then the "white" displayed on their TV will be a fundamentally different color from the "white" they see reflected off a white surface outside.
This effect is going to be found to be doubly true if you're calibrating to indoor lighting in the evening, but they watch their TV at noon in the daylight with the windows open -- because the color temperature of the environment will now be much higher than the color temperature of the screen.
A but of orange will make white look more like white does in the evening, or in firelight.
Color is a perceptual phenomenon that is not independent of surroundings and is especially tricky when you're talking about emission. Just as a piece of white paper in a candle-lit room is very different to a piece of white paper outdoors in sunlight, what is perceived as white on a TV can differ greatly depending on the room it is in or even what else is displayed on-screen.
Rather than insulting people's conception of what "proper white" is, perhaps consider that it's not quite as simple as you think.
Not to get me started on the millions of colours you paint your walls in. I did have a laugh when I found out that proprietary paint colours are a big thing, a few weeks after reading on HN about Adobe "cancelling" a colour. Proprietary colours are a thing I can suddenly talk about with repair guys. Car paints are proprietary. Kitchen panel paints are proprietary. It's a whole new world. It's not just RGB, there's gloss and sparkle to consider.
We pick an arbitrary threshold of diminished color information and call that CVD, color vision deficiency. Depending on which threshold you pick for CVD, males are anywhere from 10 to 20 to 50 _times_ more likely to have it than females. Of course, this “has / does not have CVD” binary is an artifact of us picking a threshold; the real underlying mechanism is that the distribution of wavelength tunings in the male population is much more heavily weighted towards “overlapping”.
Put another way, you have two overlapping bell curves of “how much color information can your eye cells theoretically generate” and if you drop a single point on that graph you can capture 1% of females and 10% of males to the left of it (for that 10x figure), or 0.02% of females and 1% of males to the left of the chosen point (for that 50x figure), or anywhere in between. And the fact that you can do this tells us the two bell curves very likely have different means and standard deviations.
The search term is “spectral sensitivity” if you’re interested in finding out more.
(I do know that “but it’s true” isn’t considered to be a good rebuttal to “it’s a stereotype”, but it kinda seems like it should be, and I don’t really know why it isn’t. Also, as someone with extreme CVD, color vision is just a fantastically interesting topic regardless of sex differences. The way those EnChroma glasses that “treat” color vision deficiency work is they block out a small section of the light wavelengths where CVD tends to have high overlap. This artificially increases the relative difference in activation, meaning the brain can extract more color data, with the practical result that people with CVD put on these glasses and see colors with an intensity they’ve never seen before. But it gets even cooler! For instance, did you know if we develop the technology to directly stimulate those different wavelength receptors independently of each other, we can make those receptors report “differences in relative activation” that are literally impossible to achieve with any combination of light wavelengths? That is, the cells will happily report perfectly well-formed color data to the brain, except that it’s data in a range that no brain has ever received before. The visual cortex seems like it does fairly general information processing, at least at the lower levels before we start tagging that information with e.g. emotional responses or linguistic names, so on some level our brain would probably be able to make immediate sense of this previously “out of band” information. It must be able to do so, or else CVD sufferers wouldn’t get such vivid reactions to EnChroma glasses. So it’s very plausible that this procedure would instantly unlock actual “new color experiences” for everyone. How cool is that?)
My complaint was with the way it was said, it looks immature and promoting stereotypes about color perception in daily life.
With the exception of color blindness, the difference in perception between women and men is much smaller than the variation across all humans. There are many things where we can measure a difference that is "significant" but in reality, insignificant (IE, passes a t-test with bonferroni or other multiple tests correction, but doesn't matter in any way at all during life).
Much more interesting than "seeing"/"perceiving" colors that most humans don't (example: tetrachromancy) is seeing polarization. I can see polarization but it was self-taught (see the page on Haidinger's brush and then go outside and look at the sky with polarized glasses on/off.... after a bit, you will realize you actualyl can "see" the polarization.
For instance, "Jewish people are good with money" is a social construct, caused by the Catholics banning their adherants from working in banks for centuries. There's no inherent difference between groups as far as being able to do the job. It's the result of centuries of social distortions applied to who can do what job. If the social distortions (which still happen today, often propagated by the stereotype itself) ended, the difference would cease to exist.
It's important to distinguish the difference between intrinsic differences and socially-constructed differences. And we keep discovering more differences are socially constructed than we had previously thought. Even the idea that men are worse at color perception has a significant social component. That's what the OP was referring to - the social construct caused by telling children that caring about color distinctions isn't a masculine trait. Sure, there's also an intrinsic difference, with color perception having a sex-linked genetic component. That is real. But it's not the entire story, and I'd be wary of making blanket statements that assume the intrinsic property is the only one.
https://www.newscientist.com/article/2241717-infrared-reflec...
press a button to turn the walls from black to white :)
From the TFA
But insulation matters much more in the winter; the color/shade only reduces the energy load, it doesn't dissipate it.
This substance is also used as a radiographic contrast agent and turns your poop white.
It's nice to have a room "not too warm"... unless it's a lot warmer in the street and you cant go outside!
Let's imagine a "totally white" town (white on walls, streets, roofs): the air will be quite hot, or am I misunderstanding something ? So it look to me that we will trade one problem (warm outside and inside) for another one (cooler inside and warmer outside)
I would also mention the ground (very big, planet-sized) as a heat sink, but in cities where it’s all covered with concrete and pavement it does reflect a lot of heat back which is one reason why we observe cities hotter than the country otherwise would be
However, with all these reflective surfaces you do get concerned with direct solar i.e. skiing in shorts & glare e.g. the "walkie-talkie" building [0].
Only active cooling can cool anything below the ambient temperature. 100% reflectivity can prevent it absorbing more heat, if you can achieve it, but it doesn't cool anything down.
> “Barium sulfate has reflective properties that allow us to hold below ambient temperature,” said Felicelli
That's a bit more like it: 3/4 of the way down the page, someone finally points out that paint can't cool anything, it can only stop it warming up.
Not exactly:
https://en.wikipedia.org/wiki/Radiative_cooling
Couple of videos explaining the effect
It's more complex than that. Through thermal radiation objects on the surface of Earth are also thermodynamically connected to the surface of the Sun (~6000K) and Space (~4K).
The way to cool below ambient temperature with passive cooling is to isolate from the Sun, radiation from nearby objects and and conducting heat from surrounding air as much as possible, while making the thermal connection to Space as strong as possible.
1. How to isolate from the Sun: surface reflective in the spectrum where the thermal radiation from the Sun is the strongest, which is not too surprisingly the visible light spectrum (hence this article)
2. How to isolate from surrounding objects: insulation against conduction + surface reflective in the spectrum where the surrounding objects' thermal radiation is strongest (somewhere in infrared).
3. Thermal connection with space: you want to emit in the infrared spectrum as strong as possible.
2 and 3 are seemingly in contradiction, as a surface can't be a good reflector and good emitter at the same wavelength at the same time. But just have a geometry where the surface satisfying point 2 is pointed towards surrounding objects, while the surface satisfying point 3 radiates towards space.