Ah, SPF they measure by seeing how long UVB rays take to burn skin with sunscreen versus without. PA ratings, those are for UVA—they test how much pigment darkens right after. Me, I learned this from my son's semester project printouts left on the table. But truthfully, I care less about the burn and more about the deep wrinkles I see on the fishermen who never used it, their faces like old leather against my own.
#life#career
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