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Sunblock formula for dummies
Congratulations to me. I finally figured out what the SPF number stands for.
I am pretty religious about using sunblock (that's what having cancer at the age of 29 will do to you) but I never actually knew what that number meant, aside from SPF 20=good protection. SPF 30=better protection, and so on.
The website Skin911 breaks Sun Protection Factor (SPF) down in a way that makes it easy to understand. Go figure, SPF is all about the length of time spent in the sun:
- Take the time you would normally burn in the sun without protection. 20 minutes would normally produce redness on a light skinned individual.
- Multiply that number by the SPF factor of your product. Example: with an SPF 15 X's 20 minutes of sunburn time = 15 x 20 = 300 tells how many minutes you may stay in the sun without burning. 300 minutes divided by a 1 hour of 60 minutes = 5 hours of sun protection without sunburn.
The amount of time to achieve redness with the sunblock applied determines the SPF. As people vary product results will vary on individuals in the market place.
I guess I am safe with 25 for a few hours. (Note to self: Not in Australia. Australia calls for hard-core SPF application and re-application)
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Reader Comments (Page 1 of 1)
David Kulas May 13th 2008 1:19AM
Excellent info---thanks much----being a Minnesota farm boy I got a few bad burns and lots of great tans!!!!
Now I spend about 15-20 min in the sun and thats it.
Stay safe
rrgg May 16th 2008 6:50PM
Side note--- The SPF rating *ONLY* applies to UVB rays which causes burns. It does not apply to UVA which is more responsible for skin cancer and wrinkles.
To block UVA better, look for newer products containing mexoryl, or else ones containing zinc oxide. Neutrogena claims their helioplex blocks UVA longer too.