Protecting the Face/Skin

[KnottedYet]

Weeeeeellll, sort of.

You are still absorbing radiation. I can put on spf 2, and in 20 minutes I will have absorbed as much radiation as I would have in 10 minutes naked. So I will burn. If I reapply the spf 2 after 20 minutes, I will still be burned. Because I've absorbed that radiation already and in 20 minutes more I will absorb that much again.

10 minutes naked = burned Knot
20 minutes with spf 2 = burned Knot
2 1/2 hours with spf 15 = burned Knot

but:
10 minutes naked = burned Knot
20 minutes naked = painful peeling Knot
2 1/2 hours naked = blistered crying Knot

The spf cuts down on the amount of radiation you absorb, but you are still getting radiation. The rating is based on how much radiation is being cut off, not how long it will totally protect you.

You need to reapply chemical screens because they break down with exposure to radiation (the radiation destroys the screen instead of destroying you). You need to reapply just to maintain the spf you originally had with your fresh application.

Physical blocks don't break down with radiation, so reapplying them if the previous layer hasn't worn off CAN be cumulative. I always assume it's wearing off, so I end up wearing probably a lot more spf than the bottle says.