# So, can you explain sunscreen to me? **URL:** \ **Category:** Factual Questions\ **Created:** [June 23, 2003, 9:34pm UTC](https://boards.straightdope.com/t/so-can-you-explain-sunscreen-to-me/183872 "2003-06-23T21:34:55Z")\ **Posts on this page:** 15\ **Page:** 1
**Author:** ![Lsura](https://avatars.discourse-cdn.com/v4/letter/l/7993a0/32.png) [@Lsura](https://boards.straightdope.com/u/Lsura)\ **Post date:** [June 23, 2003, 9:34pm UTC](https://boards.straightdope.com/t/so-can-you-explain-sunscreen-to-me/183872/1 "2003-06-23T21:34:55Z")
As I spent some time at the pool today, I began pondering sunscreen. See, I don’t own any (don’t yell. I watch the amount of time I spend in the sun very carefully. Still being very pale, I was allowed to be outside for no longer than 30 minutes today). Part of the reason I don’t own any is that I’ve managed to convince myself that I will gain no color on my skin at all if I use it, hence the careful timing. I don’t want to burn, just not show off ghostly white legs all summer. How does sunscreen work? What do the various SPFs mean? What level SPF should I look for? And will I gain any color if I use sunscreen or will I remain pale as butt-cheeks? ---
**Author:** ![Whack-a-Mole](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/whack-a-mole/32/141_2.png) [@Whack-a-Mole](https://boards.straightdope.com/u/Whack-a-Mole)\ **Post date:** [June 23, 2003, 10:13pm UTC](https://boards.straightdope.com/t/so-can-you-explain-sunscreen-to-me/183872/2 "2003-06-23T22:13:17Z")
Using sunscreen will still allow for a tan. Every sunscreen is rated with a ‘Sun Protection Factor’ (or SPF). An SPF of 2 means you can spend twice as long in the sun with it to get the same effect as without it. An SPF of 10 means you can spend 10x as long. So, if you are ok with 30 minutes with no sunscreen then wearing SPF-10 sunscreen would allow for 300 minutes to get the same effect. This assumes ideal coverage of the sunscreen and that it isn’t washed or sweat off. The directions will usually say you need to reapply during the day. Sunscreen works by blocking the ultraviolet rays of the sun. The ultraviolet rays of the sun are what is responsible for sunburns and tanning. ---
**Author:** ![beagledave](https://avatars.discourse-cdn.com/v4/letter/b/6de8d8/32.png) [@beagledave](https://boards.straightdope.com/u/beagledave)\ **Post date:** [June 23, 2003, 10:14pm UTC](https://boards.straightdope.com/t/so-can-you-explain-sunscreen-to-me/183872/3 "2003-06-23T22:14:50Z")
[Here](http://travel.howstuffworks.com/sunscreen3.htm) ya go. ---
**Author:** ![Monty](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/monty/32/47_2.png) [@Monty](https://boards.straightdope.com/u/Monty)\ **Post date:** [June 23, 2003, 10:29pm UTC](https://boards.straightdope.com/t/so-can-you-explain-sunscreen-to-me/183872/4 "2003-06-23T22:29:34Z")
I understand that you can use both tanning creams and sunscreen; the first gives you the illusion of not having pasty white legs and the second protects you from those cancer-causing sun rays. SPF stands for Sun Protection Factor (or near enough to that so as to not make much difference) and is designed to block certain UV rays. Here’s what [aloha.com](http://aloha.com) says the July 9, 1996 issue of the New York Times has to say on the matter: > [@](#): > > [http://www.aloha.com/~lifeguards/sun.html#spf](http://www.aloha.com/~lifeguards/sun.html#spf) > The letters S.P.F. stands for sun protection factor, but dermatologists wish people didn’t think the numbers offered a license to tan. > > A factor is a number used to multiply another number, in this case your time in the sun before burning. An S.P.F. of 2 means that if you usually start to burn in 20 minutes, using the product would, in a perfect world, let you bask twice as long before you burn, assuming that the product is fresh and full strength, that you apply enough (at least an ounce) and that you don’t swim or sweat it off. Please read the rest of the article in the link listed. So basically, I guess that if you use the appropriate amount of sunscreen but don’t use the “tan in a can” stuff, you’ll be pasty white. If you don’t use either, then the tan that ensues is the result of damaged skin. In other words: Pasty = Healthy! ---
**Author:** ![Nanoda](https://avatars.discourse-cdn.com/v4/letter/n/ce73a5/32.png) [@Nanoda](https://boards.straightdope.com/u/Nanoda)\ **Post date:** [June 23, 2003, 11:57pm UTC](https://boards.straightdope.com/t/so-can-you-explain-sunscreen-to-me/183872/5 "2003-06-23T23:57:26Z")
So sunscreen is just UV dye? ---
**Author:** ![Monty](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/monty/32/47_2.png) [@Monty](https://boards.straightdope.com/u/Monty)\ **Post date:** [June 24, 2003, 1:35am UTC](https://boards.straightdope.com/t/so-can-you-explain-sunscreen-to-me/183872/6 "2003-06-24T01:35:04Z")
Nope. The “tan in a can” stuff, as I call it, are the dyes. They’re the ones you would use if you want to get a tan without the UV exposure. Sunscreen is stuff that’s designed to filter the UV rays. FWIW, I use SPF 30 waterproof non-greasy so it, theoretically, doesn’t wash off when I swim. ---
**Author:** ![raisinbread](https://avatars.discourse-cdn.com/v4/letter/r/8491ac/32.png) [@raisinbread](https://boards.straightdope.com/u/raisinbread)\ **Post date:** [June 24, 2003, 1:52am UTC](https://boards.straightdope.com/t/so-can-you-explain-sunscreen-to-me/183872/7 "2003-06-24T01:52:36Z")
Is there a way to find out how long it takes one to get a sunburn? The only way I can think of is reminiscent of a Calvin and Hobbes strip where Dad explains that towns figure the weight limit of trucks on bridges by driving heavier ones over the bridge until it collapses and they rebuild the bridge. ---
**Author:** ![Phage](https://avatars.discourse-cdn.com/v4/letter/p/a4c791/32.png) [@Phage](https://boards.straightdope.com/u/Phage)\ **Post date:** [June 24, 2003, 2:26am UTC](https://boards.straightdope.com/t/so-can-you-explain-sunscreen-to-me/183872/8 "2003-06-24T02:26:34Z")
As a minor hijack, what exactly are the reasons behind a sunburn? Obviously the skin does not actually get hot enough to burn, so I suspect that the UV fries a protein or breaks down some chemical. ---
**Author:** ![raisinbread](https://avatars.discourse-cdn.com/v4/letter/r/8491ac/32.png) [@raisinbread](https://boards.straightdope.com/u/raisinbread)\ **Post date:** [June 24, 2003, 2:34am UTC](https://boards.straightdope.com/t/so-can-you-explain-sunscreen-to-me/183872/9 "2003-06-24T02:34:58Z")
Perhaps this site will help you, **Phage**. [http://www.solumedia.com/sunscreen1.htm](http://www.solumedia.com/sunscreen1.htm) ---
**Author:** ![Nanoda](https://avatars.discourse-cdn.com/v4/letter/n/ce73a5/32.png) [@Nanoda](https://boards.straightdope.com/u/Nanoda)\ **Post date:** [June 24, 2003, 11:11am UTC](https://boards.straightdope.com/t/so-can-you-explain-sunscreen-to-me/183872/10 "2003-06-24T11:11:42Z")
> [@](#): > > \*Originally posted by Monty \* > \*\*Nope. The “tan in a can” stuff, as I call it, are the dyes. They’re the ones you would use if you want to get a tan without the UV exposure. Sunscreen is stuff that’s designed to filter the UV rays. FWIW, I use SPF 30 waterproof non-greasy so it, theoretically, doesn’t wash off when I swim. \*\* When I say “dye”, I mean like UV coloured paint (which would absorb UV rays), not brown dye, which is what I presume most fake’n bake products are. Something that “filters” a particular colour would end up _being_ that particular colour, no? ---
**Author:** ![Monty](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/monty/32/47_2.png) [@Monty](https://boards.straightdope.com/u/Monty)\ **Post date:** [June 24, 2003, 1:38pm UTC](https://boards.straightdope.com/t/so-can-you-explain-sunscreen-to-me/183872/11 "2003-06-24T13:38:00Z")
Well, Nanoda, the UV aren’t exactly a visible color. ---
**Author:** ![scr4](https://avatars.discourse-cdn.com/v4/letter/s/59ef9b/32.png) [@scr4](https://boards.straightdope.com/u/scr4)\ **Post date:** [June 24, 2003, 1:44pm UTC](https://boards.straightdope.com/t/so-can-you-explain-sunscreen-to-me/183872/12 "2003-06-24T13:44:08Z")
> [@](#): > > \*Originally posted by Nanoda \* > \*\*Something that “filters” a particular colour would end up _being_ that particular colour, no? \*\* Actually, a dye is something that absorbs every other color. Red dye absorbs green and blue light and transmits red light, so it looks red. I guess you could call sunscreen “visible light dye.” It transmits visible light and absorbs UV. ---
**Author:** ![In\_Conceivable](https://avatars.discourse-cdn.com/v4/letter/i/4bbf92/32.png) [@In\_Conceivable](https://boards.straightdope.com/u/In_Conceivable)\ **Post date:** [June 24, 2003, 1:48pm UTC](https://boards.straightdope.com/t/so-can-you-explain-sunscreen-to-me/183872/13 "2003-06-24T13:48:14Z")
Does anyone one else find sunscreen amazing? I love the fact that I can apply it and then hours on the boat with out turning into a lobster. **Lsura** : Yes, you can get a tan and even burn after applying sunscreen. As others have said, it just takes longer depending on the SPF. I am very pale too and always want to get just a tiny bit of color. If I am going to be spending the day outside I usually wait 20 or so minutes before I put on the sunscreen. ---
**Author:** ![Nanoda](https://avatars.discourse-cdn.com/v4/letter/n/ce73a5/32.png) [@Nanoda](https://boards.straightdope.com/u/Nanoda)\ **Post date:** [June 24, 2003, 9:45pm UTC](https://boards.straightdope.com/t/so-can-you-explain-sunscreen-to-me/183872/14 "2003-06-24T21:45:32Z")
Nuts. I think **scr4** is right. I was thinking about laundry brightening - some clothes detergent manufacturers use a [dye](http://www.planetinc.com/ull.htm) to make clothes [seem “whiter”](http://isaac.exploratorium.edu/~pauld/activities/fluorescence.html). Apparently the particles fluorece blue when exposed to UV. I guess what “colour” it is depends on whether the sunscreen [reflects or absorbs](http://www.sunscreens.net/) the UV wavelength. ---
**Author:** ![Peach](https://avatars.discourse-cdn.com/v4/letter/p/67e7ee/32.png) [@Peach](https://boards.straightdope.com/u/Peach)\ **Post date:** [June 24, 2003, 10:32pm UTC](https://boards.straightdope.com/t/so-can-you-explain-sunscreen-to-me/183872/15 "2003-06-24T22:32:36Z")
> [@](#): > > \*Originally posted by In Conceivable \* > \*\*Does anyone one else find sunscreen amazing? I love the fact that I can apply it and then hours on the boat with out turning into a lobster. > > **Lsura** : Yes, you can get a tan and even burn after applying sunscreen. As others have said, it just takes longer depending on the SPF. I am very pale too and always want to get just a tiny bit of color. If I am going to be spending the day outside I usually wait 20 or so minutes before I put on the sunscreen. \*\* i love sunscreen too because it protects my skin. I use it all the time even when its cloudy. The best kinds to get are the ones with ZINC OXIDE (usually found in baby sunscreens) because it causes the rays to actually “bounce” off you. Brilliant stuff:D