Are All Similar Strength SPF and UPF Sun Protection the Same at Decreasing UV Light Exposure?

Overview

Here in sunny SoCal, sun protection is important for all outdoor activities including youth sports to decrease the risk of skin cancer. I hypothesize that a lotion sunscreen that can be spread more evenly will afford better sun protection and lower UV light exposure. Also, both UPF 50+ and SPF 50 should afford similar over 98% sun protection. Sun Beads and Cyanotype Sun Paper change color when exposed to UV light.1,2 In my pilot experiments, there was minimal color change in the Sun Paper, so only Sun Beads were used. The 1st experiment tested 3 types of SP 50 sunscreen, the 2nd experiment added 3 shirt types with UPF, and the 3rd experiment added 2 UPF items and UV400 sunglasses. Interestingly, the results showed that SPF 50 spray sunscreen had the best sun protection with the Sun Beads, only allowing 0.5 UV index exposure. SPF 50 lotion and roll-on stick allowed 1.0 and 1.5 UV index exposure, respectively. All the UPF and UV 400 items afforded 0 UV index exposure, similar to the + control. In conclusion, the spray type sunscreen offers the best sunscreen protection. In repeated experiments using the same clear wrap, possibly due to the spray sunscreen evaporating, the lotion type sunscreen became better.  The roll-on stick type sunscreen which I use, had the worse sun protection.  All the UPF items and UV 400 sunglasses afforded better sun protection than all the SPF 50 types of sunscreen, possibly due to the items being solid.

Competition history

• CSEF 2026 Product Science (Junior Division) · Entry J-19-16

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