Indispensable during past heat waves: sunscreen. Eric de Kruijk dives into the fascinating science behind this preventative.
Also this summer vacation, there was another product that I used almost every day with great dedication and in great amounts: sunscreen. Or actually we should say “anti-sunscreen”, but since that’s not a language column, I’ll leave it at that. I discovered that there was something special hidden in such a cream when I accidentally applied a thick layer of body lotion. That night I slept with a red head and painfully burned skin.
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glacier cream
Our skin does not burn from the perceived heat of the sun, but from ultraviolet rays. The short wavelengths of this radiation are outside the spectrum of what can be seen with the naked eye. But this invisible radiation can, in addition to painful burns, cause significant DNA damage, which in the long run increases the risk of developing tumors.
For centuries, people have used a powder, oil, or herbal mixture to prevent skin staining. Not because of health, but mainly because dull skin was “among the wealthy”. After several scientists showed that UV rays could cause cancer around 1880, the search for better protection slowly began. Numerous inventors created ointments, but the main basis for the current sunscreen was laid by a young chemistry student and mountaineer Franz Greiter.
In 1938, Greater climbed Mount Pease Bowen on the border between Austria and Switzerland, after which he returned home with burning skin so painful that he saw his scientific task as working on a good protective ointment. It took a few hot summers before the first modern commercial sunscreen was launched in 1946: Gletscher Crème.
white fog
Sunscreen contains two different types of molecules that provide a protective effect. First, a mixture of organic molecules, such as avobenzone and homosalates, is needed that absorbs a lot of UV light and converts it into a less harmful form of energy: heat. Creams that absorb the entire UV spectrum contain a wide mix of these molecules because each type is suitable for a specific wavelength. For example, avobenzone absorbs mainly UV-B (longer wavelength) and homosalate mainly absorbs UV-B (shorter wavelength).
“You can see the absorption effect of sunscreen with your own eyes”
In addition to these organic molecules, many creams also contain inorganic molecules that act as UV filters. Most often these are zinc oxide and titanium. These substances remain on the skin and partially convert ultraviolet rays into heat, but also partially reflect the radiation, so that it does not reach the skin at all. However, what many consider the disadvantage is that it leaves a white film on the skin. The solution was that chemists reduced the zinc and titanium particles into nanoparticles (smaller than 200 nanometers). In this way, UV filters hardly leave a white layer. There are currently increasing indications that these nanoparticles are harmful to coral reefs and other marine life. So maybe we should take a little white haze for granted after all.
If you want to see the effect of absorbing sunscreen with your eyes, you should take a picture of your skin with a special UV camera. (I suppose, of course, that KIJK readers always have such a device at home.) The result is amazing. Since the filters in the cream mainly absorb ultraviolet light, well-lubricated skin will look on the ultraviolet image as if it were completely painted black. A photoshoot is also a good idea if you’re in doubt about whether you’ve covered yourself with sunscreen or body lotion.
This column is also found in It’s 9/2022.
Photo: HIFLEX
