Naked Science Forum

General Science => General Science => Topic started by: Keola on 24/05/2009 17:59:25

Title: How does sunscreen work?
Post by: Keola on 24/05/2009 17:59:25
I've allways wondered how sunscreen protect you? I'm guessing it "takes the hit" for your skin somehow, but how does it actually work?

Also is it true you can use lower protections once you've started to get a tan? The general idea beeing your skin is somehow "stronger" or more well protected on it's own when it's been exposed to the sun for a while.... ? [???]
Title: How does sunscreen work?
Post by: lightarrow on 24/05/2009 20:05:10
Quote from: Keola on 24/05/2009 17:59:25
I've allways wondered how sunscreen protect you? I'm guessing it "takes the hit" for your skin somehow, but how does it actually work?
Essentially, a sunscreen reflects off UV radiation.
Quote
Also is it true you can use lower protections once you've started to get a tan? The general idea beeing your skin is somehow "stronger" or more well protected on it's own when it's been exposed to the sun for a while.... ? [???]
Yes, the dark pigments of the tun absorb the UV radiation preventing it to penetrate the skin.
Title: How does sunscreen work?
Post by: Bored chemist on 24/05/2009 20:46:37
Most sunscreens absorb UV rather than reflecting it. The enegery is degraded to heat.
Title: How does sunscreen work?
Post by: Karsten on 25/05/2009 01:30:50
Quote from: Bored chemist on 24/05/2009 20:46:37
Most sunscreens absorb UV rather than reflecting it. The enegery is degraded to heat.
That is interesting. Would that mean I am getting hotter if I put on this kind of sun screen? In a noticeable way?
Title: How does sunscreen work?
Post by: lightarrow on 25/05/2009 08:24:47
Quote from: Bored chemist on 24/05/2009 20:46:37
Most sunscreens absorb UV rather than reflecting it. The enegery is degraded to heat.
Some internet pages explains as you do, some in the opposite, for example this one:
http://chemistry.about.com/od/howthingsworkfaqs/f/sunscreen.htm
Title: How does sunscreen work?
Post by: Bored chemist on 25/05/2009 10:01:59
Quote from: Karsten on 25/05/2009 01:30:50
Quote from: Bored chemist on 24/05/2009 20:46:37
Most sunscreens absorb UV rather than reflecting it. The enegery is degraded to heat.
That is interesting. Would that mean I am getting hotter if I put on this kind of sun screen? In a noticeable way?

Not noticably. Without the sunscreen the UV would be absorbed by your skin and largely converted to heat anyway.

Also there's a difference between sunblock which is generally white and reflects the UV; and suncscreen which isn't and doesn't