Hot, hotter, hottest Why you sweat faster in a black T-shirt than in a white one
You go out into the sun in your favorite shirt, which is of course black. And you immediately regret it: Why is it actually even hotter than when you're wearing white?
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- You go out in the sun in your favorite black shirt in summer - and regret it shortly afterwards.
- Why do people sweat more in black clothes than in white ones?
- You've probably heard the quick answer before: black color absorbs light, which is why it warms up.
- This is correct in principle, but it doesn't explain everything.
Anyone who has driven to Italy on vacation in a black car in the past knows that fun is something else.
Because in the black car (without air conditioning, as used to be the case), the temperatures tended to rise above a tolerable level.
But why is that?
It starts with the fact that color is only created by light
You've probably heard the quick answer before: black paint absorbs light, which is why it warms up. This is correct in principle, but it doesn't explain everything.
It starts with the fact that color is actually created by light. It is not the case that it is present on an object and then does something with the light.
The reverse is true: the object has a surface with certain chemical properties that do something with the light.
More precisely, the molecules in the surface do something to the light. They interact with it. You need to know that light also consists of small particles, which are usually represented as waves.
These particles collide with the molecules - and depending on the nature of the molecules, they either absorb the light particles and their energy or repel them.
If they repel the light particles, this is referred to as reflection. If they take them in, they absorb them. The result of absorption is that the absorbed light particles cause the molecules in the surface to vibrate with their energy. These movements generate heat.
Water swallows everything except blue
In everyday language, we like to say that the surface swallows the light. This is not a bad image, but usually only parts of the light are swallowed, namely the parts with a certain wavelength.
All wavelengths combined are referred to as the wave spectrum. We humans cannot perceive large parts of this spectrum at all, for example radio waves, X-rays or UV rays.
The small remainder are our colors, with red light having the longest wavelength (650 to 780 nanometers) and violet light the shortest (380 to 420 nanometers).
If the chemical composition of the surface is such that it absorbs virtually the entire spectrum and reflects almost nothing, it appears black. If everything is reflected, it appears white.
There are all kinds of gradations in between. Water, for example, mainly absorbs long-wave light (i.e. red, orange, yellow and green) and reflects blue light. That's why the oceans are blue.
Black clothing provides better protection against sunburn
However, whether you only sweat or sweat a lot in a black T-shirt in the current temperatures also depends on the material and how tightly you wear the clothes on your body.
Airy linen, for example, is cooling, but cotton is also good. At least better than synthetics such as polyester or nylon.
Airy is a good keyword, because you've probably noticed that people who live in countries where it's often hot don't all just walk around in white.
This is not necessary because the heat is easily dissipated if the clothing is airy enough. A study with Bedouins a few years ago even showed that this removal works at least as well with black clothing as with white.
Black clothing has another advantage: because it not only absorbs visible light, but also UV radiation, you are better protected from sunburn with it than with light-colored clothing - at least with very thin fabrics.
