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> Most surprisingly, Nxylon remains black even when coated with an alloy, such as the gold coating applied to the wood to make it electrically conductive enough to be viewed and studied using an electron microscope. This is because Nxylon’s structure inherently prevents light from escaping rather than depending on black pigments.

I don't follow this at all. If it's coated with an alloy, Nxylon isn't on the surface of the object anymore, the alloy is. So the alloy should be reflecting light. What am I missing?

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I interpreted this along the lines of it not being a pigment, rather it's black because something about it's physical structure at a small scale causes light to not reflect back. Adding a thin coating of gold would not necessarily change that structure so it would continue not reflecting light.

^ pure conjecture

I believe it's something called "structural absorption", similar to what happens on birds of paradise feathers [1]

[1] https://www.nature.com/articles/s41467-017-02088-w

I wonder if this pattern is considered similar to fractals? Or would that work even better? I recently learned that we have figured out how to produce fractal light from lasers as well which sounds quite interesting and useful.

Maybe the reason radio waves travel poorly through trees is due to the leaves having a fractal-like structure as well? And since light is also just electromagnetic radiation too, it makes sense that this phenomenon could also be used to absorb light itself, if I'm understanding correctly. I wonder if this is how stealth paint on aircraft works?

I'm way out of my depth here, but I think this comparison to the birds of paradise feathers makes the most sense in terms of me visualising what Nxylon would look like with a thin metallic coating

> Adding a thin coating of gold would not necessarily change that structure

My confusion is that I would normally expect a layer of gold not to permit any light to pass through. The underlying structure wouldn't be receiving any light, so there would be no photons to trap. Apparently a layer of gold can be applied thinly enough to transmit appreciable light, though.

Gold foil can be beaten to under 2 micrometers.

https://en.wikipedia.org/wiki/Gold_leaf

This part of the article confused me, because what does a black pigment do if not "inherently prevent light from escaping"? That's kind of just the definition of absorb.

A layer of very thin gold can be transparent.

I see, thanks for filling that in.

Famously seen on the Apollo space suit sun visors. Their gold layer is thick enough to look gold, but thin enough that you can see through it:

http://heroicrelics.org/apollo-wwwttm/apollo-suit-a7l-leva-v...

You can see through it at least in part because of the tint/opacity effect, where there is more light on the outside than the inside. It's why you can't see through it the other way around (it's reflective, you don't see the astronauts' eyes).

That would imply the result of overlaying Nxylon with this would be gold-colored, not ultra-black..

Right, but less reflective than solid gold, since some of the light is going _though_ instead of bouncing off

So as you make the layer even thinner than the sun protection on those Apollo visors, you have even more light going through, and even less that can bounce off

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