These creams have some chemical that blocks the UV with some capacity, say a factor of 50. Why can’t I apply two layers of this cream to now get a 100 factor equivalent protection?
I asked the chemist at the store and they said it’s not how it works and that the highest protection factor they have is 75 (which was super expensive).
What gives?
Edit: Thank you for those super informative answers.
Be aware light clothing can still transmit enough light to burn. My bullshit test is “can I look at the sun through this fabric or does it hurt?”. It’s a little conservative, but it’s good enough for me if I plan to be out for 8 hours. I actually just got burned shirtless last week on one side. With a light, black, sports shirt the next day, I was in mild burning pain when the sun hit my burned side. It wasn’t just heat, as lifted the fabric off my skin still hurt the same.