It just occurred to me yesterday, other than maybe “wet things absorb more light” that I really have no idea.
Just a few examples:
– Sweat patches on a grey t-shirt are dark grey.
– Rain on the road, or bricks end up a darker colour.
– (one that made me think of this) my old suede trainers which now appear lighter and washed out, look nearly new again once wet, causing the colour goes dark.
In: Physics
The water allows more light to transmitted through the thing, and if that light then hits a surface, behind the wet something, that absorbs it then less light gets reflected back, hence the darker appearance.
So the color is more….saturated?
Here’s a great gif that demonstrates this concept marvelously. [GIF](https://tenor.com/XHEf.gif)
I have a t shirt that actually gets lighter in color when wet. I still have no idea how it works.
Because of all the super complicated answers here allow me to simplify it into a *real* ELI5:
Water sitting above a surface, as in a puddle or lake, reflects light off it’s surface. But water absorbed into something makes surfaces *less* reflective. Less reflection equals less light going toward you. Think of it like if a mirror were made out of cloth. If you wet the mirror it will sag and fold over on itself and then you can’t see your reflection. Water is scattering the light.
And a wet white t shirt turns what color?
My guess would be related to resulting density (water is the ultimate solvent) from water filling the voids in the subject material, which is frequently also experiencing oxidation of some sort, which makes the subject appear whiter/lighter when dry. (think of gray weathered wood when it gets wet).
With regard to light, the water creates a kind of covalent bond (not really, but the water is bonding with the subject temporarily until it dries), improving the density and creating a visually darker result.
Aside from the answers you get here, check out past similar questions
https://old.reddit.com/r/explainlikeimfive/search?q=Darker+wet&restrict_sr=on
Light bounces back into your eyes when there is less stuff for it to get lost inside. Wet stuff has more places for it to get lost, and so less of it bounces back in your eyes. Less light = more dark.
After reading certain answers, I’m beginning to think water traps some of the incoming and/or outgoing light by the phenomenon of Total Internal Reflection thus making wet things appear darker.
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