Originally Posted by Abbey32
I didn't know you could get a tan with a SFP. Interesting. How is that?
Because an SPF only blocks part of the rays - the lower the SPF, the less protection it affords.
SPF Number x Time to Burn Without Sun Protection = Time to Burn while wearing sunscreen
Example: If your skin would burn in 10 minutes in the afternoon sun without any sun protection, and you applied a sunscreen with an SPF 15, you would have 15 x 10 = 150 minutes (2.5 hours) before you would burn.
Percentage of Protection from damaging UV rays:
SPF 15 = 92%
SPF 30 = 97%
SPF 40 = 97.5%
All sunscreens protect from UVB rays, but only “Broad-Spectrum” sunscreens protect from both UVB and UVA rays. UVB rays affect the top layers of the skin and are responsible for burning. UVA rays affect the lower layers of the skin and are responsible for aging.