This evening I was at the local swimming pool and at the end of my line there was a man sitting in the sun, well built, type suburbian Adonis. He sat there quite a long time. He was wearing dark diving goggles, but not for swimming. He probably just didn’t want the reflection on the water to disturb him with glare, while he was watching the people swimming in the evening sun. He was sun bathing.
And every time I came swimming past him I had to keep myself from saying to him: “But you do know that the sun doesn’t tan you at this time of the day, but only makes your skin older, don’t you?”.
Now – I have been a lovable but sometimes mildly annoying smarty pants for quite a while now 🙂 and as such I know, that this kind of unsolicited advice is often not well received. So, I finished swimming my rounds and kept my mouth shut, happy that I still have the platform of this blog, to elaborate on the whole thing with UV-A and UV-B – in peace and quiet. So here goes:
UV-A and UV-B

The skin gets darker primarily through UV-B radiation. UV-A radiation can penetrate more deeply into our skin and contributes stronger to an older looking skin.
UV-C does usually not reach through the atmosphere, but UV-A and UV-B rays can damage the skin, destroying molecules and thus be harmful for humans.
If the pretty boy at the pool wanted the optimal ratio of many tanning UV-B rays and minimal aging UV-A rays, he would need to sunbathe at noon. Then of course not so long, but a much shorter time.
In the evening, because of the low angle of the sun rays, less UV-B rays can reach our skin, but many UV-A rays. That is why most people do not get sunburnes in the evening sun. But wrinkles.
UV-Index
For us to know how much is the danger of UV induced damage to our health every day, the expanded daily weather forecast contains info about hte “UV-Index”. On a scale of 1-12, it indicates how much UV radiation there is to espected today.
Seen as non-hazardous are UV-Index of 0-2.
Everything above it calls for sun protection, so: glasses, hats, clothes and sun screen. #SlipSlopSlapandWrap
The UV radiation is highest between 11: 00 and 15: 00 o’clock.
Of course, this applies to average altitudes. The higher you get into the mountains, the stronger the UV radiation.
In southern countries, the UV radiation is even more intense, because there the beam angle of the sun is steeper.
The Shadow Trick
Well… I don’t like rules, where I have to remember so many exceptions and that’s why I rather use the shadow trick to find out how long I can stay in the sun. I will explain how it works in this short 3 min. video:
“The shorter the shadow, the more solar radiation. This applies to every time of day and all seasons, and every place on Earth.” (Meffert et al)
To avoid sunburn you should only stay in the Sun, as long as your own shadow is longer than you yourself. You can use also an object to compare height and shadow, a cell phone, for example, like shown in the video.
You should be under an umbrella, if the shadow is shorter than the body size. This corresponds to a UV-Index of 3-7. Sunscreen is now definitely necessary.
If the length of the shadow reaches only a quarter of the body’s length, you should not be outdoors anymore.
Easy enough, right?
dminder – digital support
Determine your skin type
Even without a smart phone it is quick and easy to determine the skin type – and if you have never done this, then now is the time!
You tan quickly and almost never have sunburns? Congratulations, you’re skin type 4. But you too have to protect your sceen from UV damage.
You never tan and get sunburns everytime you get in contact with the sun? You’re skin type 1. The shortest tanning times apply to you.
Self-protection of the skin
How long exactly you can stay in the sun riskfree, I have compiled here. The general information about the sunburning time that doctors usually give out, always refers to midsummer sun on a midday (UV index 8). But there are also other times….
Times given in minutes. The countdown to the sunburn so to speak.
1 long shadow |
2 long shadow |
3 | 4 same shade |
5 a short shadow |
6 a short shadow |
7 a short shadow |
8 Quarter shade |
||
I
|
40 | 20 | 13 | 10 | 8 | 6 | 5 | 5 | |
II
|
80 |
40
|
26
|
20
|
16
|
13
|
11
|
10 | |
III
|
120
|
60
|
40
|
30
|
24
|
20
|
17
|
15 | |
(IV)
|
200
|
100
|
66
|
50
|
40
|
33
|
28
|
25
|
|
V
|
360
|
180
|
120
|
90
|
72
|
60
|
51
|
45
|
The suburban Adonis finally went to swim or cool off, before I could give him the link to my Web page. If you know sun worshippers and you wish them well and want them to healthy enjoy the Sun, please forward this text them. Thank you!
Sources:
Hans Meffert, Helmut Piazena, Peter J. Meffert, dermatological centre Berlin, how the sun shines strong now? Shadow rule and current UV index