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.

  • Lasherz@lemmy.world
    6·
    5 months ago

    If you’ve ever used a UV camera it’s pretty clear that much like lotion not absorbing after a certain point, there’s a limit to how dark your skin gets with a given sunscreen. Also that there’s a massive difference between brands and formulas. I had some photos I took with one but can’t find them. If I do later I’ll update.

    Searched but couldn’t find them. Did find a conversation though where I used it to show most cars in a parking lot have UV blocking windshields but every other window is transparent unless they have tint