MUNDANE MYSTERIES: What does SPF stand for? How do they come up with the number?

MUNDANE MYSTERIES: What does SPF stand for? How do they come up with the number?

Summer is officially here and I hope you’re using the correct SPF sunscreen. But what does SPF stand for? And how do they come up with the number?

SPF stands for Sun Protection Factor, and the number beside it tell you how well the sunscreen protects your skin against sunburn. But there is a very specific formula they use to determine which SPF is for you.

Here is how it’s explained:  The number of seconds it takes a patch of skin to slightly redden when covered in sunscreen is divided by the number of seconds it takes to slightly redden when there is no sunscreen applied. Say it took 300 seconds for skin to burn with sunscreen, and 10 seconds to burn without it. 300 is divided by 10, which is 30. The SPF is 30.

Interesting! I’m usually an SPF 50 or higher. Have to keep these sunburns away.

 

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