Structural Color

April 8, 2023 12:32 AM

"A Boeing 747 needs about 500 kilograms of paint. He estimates that his paint could cover the same area with 1.3 kilograms."
posted by blue shadows (28 comments total)

Archive link to bypass the paywall.
posted by Dysk at 12:38 AM on April 8, 2023 [2 favorites]

It's worth noting that this weight reduction was why American Airlines used livery that kept most of the plane unpainted for many years.
posted by NoxAeternum at 12:48 AM on April 8, 2023 [6 favorites]

The cooling effects mentioned in the article are a nice side effect too!
posted by freethefeet at 12:57 AM on April 8, 2023

Direct link to the paper (archive link), with lots of pretty colours in the diagrams.
posted by a car full of lions at 12:57 AM on April 8, 2023 [3 favorites]

I love the idea of airplanes looking more like butterflies.
posted by lock robster at 1:07 AM on April 8, 2023 [1 favorite]

As the article points out, the difference between a building roof that hits 30 centigrade on a hot day, and one painted so as to only get to 25 under the same conditions - represents a massive potential to save on AC cooling energy. That one might turn out to be one of the most important applications.
posted by rongorongo at 3:20 AM on April 8, 2023 [11 favorites]

“Even building products where aesthetically people would like a darker tone—whether it's a decking or siding—but of course that increases the heat load on the building.”

Even before I got to this point I was thinking: where can I buy this paint? Our house could really use a refresh, but I like bold colors and our siding is steel and these things do not go well together. Until now??
posted by eirias at 3:43 AM on April 8, 2023 [1 favorite]

the difference between a building roof that hits 30 centigrade on a hot day, and one painted so as to only get to 25 under the same conditions - represents a massive potential to save on AC cooling energy.

This is exactly why I am made so insane by all the greenfield housing development that's been going on in Australia for the last 30 years. It's the same shit everywhere - what used to be paddocks is now a vast expanse of boundary-to-boundary charcoal-grey roof tile with a great big chiller sticking out the top of every roof.

What the fuck, architects? Developers? Planning authorities?

The first change I made to our place after moving in here was to get our slightly dilapidated steel roof painted white.
posted by flabdablet at 3:46 AM on April 8, 2023 [11 favorites]

Jock, the painter, often would thin his paint so it would go further. So when the Church decided to do some deferred maintenance, Jock was able to put in the low bid, and got the job. As always, he thinned his paint way down with turpentine.

One day while he was up on the scaffolding -- the job almost finished -- he heard a horrendous clap of thunder, and the sky opened.

The downpour washed the thinned paint off the church and knocked Jock off his scaffold and onto the lawn among the gravestones and puddles of thinned and worthless paint.

Jock knew this was a warning from the Almighty, so he got on his knees and cried: “Oh, God! Forgive me! What should I do?”

And from the thunder, a mighty voice: “REPAINT! REPAINT! AND THIN NO MORE!”

- via Fr. Tommy Lane
posted by fairmettle at 4:13 AM on April 8, 2023 [56 favorites]

As the article points out, the difference between a building roof that hits 30 centigrade on a hot day, and one painted so as to only get to 25 under the same conditions - represents a massive potential to save on AC cooling energy. That one might turn out to be one of the most important applications.

I’d be curious to see how well it works. I have a flat roof and I live in the desert. The roof is coated and periodically gets recoated with a white elastomeric coating. This stuff is designed specifically to reflect sunlight and it does very well, reflecting well over 90%. On a 105° day, the roof is cool to the touch (oh but you’re gonna go snowblind, that’s for sure.) If this new coating can do better, especially if it can work on walls, it could save a lot of people a lot of money on AC in the summer.
posted by azpenguin at 5:26 AM on April 8, 2023 [1 favorite]

Mod note: Multiple comments removed. Let’s end the archive derail.
posted by Brandon Blatcher (staff) at 7:27 AM on April 8, 2023

This is exactly why I am made so insane by all the greenfield housing development that's been going on in Australia for the last 30 years. It's the same shit everywhere - what used to be paddocks is now a vast expanse of boundary-to-boundary charcoal-grey roof tile with a great big chiller sticking out the top of every roof.

What the fuck, architects? Developers? Planning authorities?

Eh it's not the worst idea to have dark roofs. I live in Melbourne as well (looking at your Google Maps pin) and I have the heating turned on continuously for 9 months of the year, between March to November, to maintain an indoor temperature of 23°C against, what is now just 10°C outside right now.

As for cooling... I need to maintain a max of 27°C indoors and the building is insulated enough that yeah, I only turn on the cooling about 10 days of the year, there's a few hot days in December and January.

So 270 days of heating versus 10 days of cooling, it's not the worst idea to get a dark roof and soak up some free solar energy and soak in some heat into the house.

My home is 7.6 NATHERS rated so I have given it some serious thought... with advances in building technology there's been a lot of things that seem counter-intuitive, for example, there have been some arguments that in hot climates you don't want insulated foundations since you get a moderating effect from ground cooling in hot days.
posted by xdvesper at 8:50 AM on April 8, 2023 [2 favorites]

It's worth noting that this weight reduction was why American Airlines used livery that kept most of the plane unpainted for many years.

Nox! My favorite Aerospace tale! It always bothered me that was always given as the reason since, if it saved that much we'd see more brands doing that, especially after spikes in gas prices.

Apparently the trade offs make it a wash for many airframes, per Boeing.

I recently went on a rabbit hole on Paints and Coatings following this from Practical Engineering and always thought advances in material science that prevent corrosion would make an interesting basis for a science fiction story. I'm already embarrassed for how excited I'm going to be if I meet a materials engineer at a party, that person better be ready for some questions.
posted by midmarch snowman at 9:02 AM on April 8, 2023 [3 favorites]

This is really fascinating.

Particularly the bit about being to make basically any color with just aluminum. My dad worked in automotive color, and some additives get really expensive. There's been a huge spike in the price of cobalt as electric vehicles become more common, so cobalt blue paint/colorants have become much more expensive. If you can just make whatever color you want, that becomes a nonissue.

Non-fading colors would be huge too, in terms of labor saving and product longevity. This might actually be a problem for auto manufacturers: part of how they get people to buy a new car more frequently than they really need to is to make the paints discolor right about the time the warranty runs out. (They literally test and target for this!)

Really exciting stuff though!

Ooh I wonder if it is possible to make things *shift* color. If you physically shift the heights of these tiny piles of aluminum by a few nanometers would it change their colors? I don't know if these structural colors work that way but if they do, you could make a non-backlit display with the vividness of an illuminated manuscript.
posted by JDHarper at 9:20 AM on April 8, 2023

Do you have to confirm that you are not Anish Kapoor, you are in no way affiliated to Anish Kapoor, you are not purchasing this item on behalf of Anish Kapoor or an associate of Anish Kapoor?
posted by MrGuilt at 9:31 AM on April 8, 2023 [9 favorites]

Does an airplane *need* paint or is it just for marketing/vanity purposes? The article didn't seem to explain that. Aluminum doesn't really rust as far as I know.
posted by mrgoldenbrown at 9:31 AM on April 8, 2023

Not just vanity. White/light colors reject insolation better than bare metal.
posted by GCU Sweet and Full of Grace at 11:47 AM on April 8, 2023

if I meet a materials engineer at a party, that person better be ready for some questions

I used to hang out with some MatSci researchers at Penn State when my wife was there getting her PhD. Absolutely fascinating some of the work with ceramics they were doing. Some of the labs had mysterious funding sources and were reluctant to talk too much about their work.
posted by slogger at 12:31 PM on April 8, 2023

Aluminum doesn't really rust as far as I know.

There's a difference between rust and corrosion, and paint is a good way to protect against corrosion.

Also, this whole thing is fascinating. It reminds me of thin film interference and coloring (especially thermal bluing) of steel. Clock- and watchmaking traditionally has blue parts (mostly screws and the hands) made by carefully heating steel and nothing else. You can of course find some information on this in Clickspring videos, but I happened to find something to read that actually goes into it a bit rather than just saying it's a thing.
posted by cardioid at 1:00 PM on April 8, 2023 [1 favorite]

Arizona State University’s Biomimicry Center is one of the few places you can get a degree in Biomimicry, which is primarily an engineering degree, but which requires a lot cross-diciplinary study. Some of the work they've pioneered includes a hotel modeled after termite mounds which eliminated the need for A/C and a kevlar-like material modeled on spider web silk.
posted by CheeseDigestsAll at 1:37 PM on April 8, 2023 [6 favorites]

If this paint indeed works and airlines can haul 500kg more on every flight, they will absolutely just find a way to add another row of seats so they can sell a few more tickets.
posted by zardoz at 2:08 PM on April 8, 2023 [1 favorite]

After reading the article I wasn't sure whether the nature of the structural colour was a property of the surface or if it was a property of the nanites of aluminum on the surface. Because if it's the latter, it sounds like they've invented a way to make pigments out of aluminum that can be precisely targetted at a certain chroma, saturation and tint. Which would also be mind blowing for artists who could have safe pigments at a constant cost.
posted by fatbird at 2:09 PM on April 8, 2023

The paint flecks have a 3-D surface to make the colors. Will it be affected by dirt and grime? Can it be washed at all? It does seem to be in the "lab","experimental" phase. I like the idea of diffraction colors!
posted by jjj606 at 4:02 PM on April 8, 2023

Blue bird feathers are structural color and they get dusty and rained on and cleaned off and stay blue.

(All blue birds? Many, at least.)
posted by clew at 5:39 PM on April 8, 2023 [1 favorite]

If this paint indeed works and airlines can haul 500kg more on every flight, they will absolutely just find a way to add another row of seats so they can sell a few more tickets.

If ten 100-seat planes become 112-seat planes then you can take the same number of people using just 9 planes instead of 10. Any amount of fuel you don't have to burn hauling paint reduces carbon emissions.
posted by straight at 11:10 PM on April 8, 2023 [3 favorites]

Did somebody say "paint", Gabriels Horn Paradox - Numberphile - YouTube.
posted by zengargoyle at 12:46 AM on April 10, 2023

Also, weight of paint was why the fuel tank of the first Space Shuttle was white and the following were that drab orange/brown... It saved weight.
posted by zengargoyle at 1:06 AM on April 10, 2023

It’s neat, but I don’t want to be the guy painting a door with a raisin.

I always thought the trick would be using lasers to etch glass or metal to match your desired wavelength of light. You could even get lighter as you paint the surface.
posted by KBGB at 9:01 AM on April 12, 2023 [1 favorite]