The situation is frequent and familiar to most kids in the summer. You are at a picnic enjoying Cheetos. With no place to wipe your Cheeto fingers, you wipe them on your shirt. The question we try to answer in this experiment is, do Cheetos make an effective sunblock? Does wiping your fingers on your shirt increase the sunblock protection of the shirt?
To do this experiment, we first ground up some Cheetos into a powder.
Then we took the Cheeto powder, some 50 SPF sunblock, and some towels and headed to the back yard. We exposed our stomachs to the sun and put a strip of sunblock and a stripe of cheeto powder.
We tanned in the sun for 20 minutes. It is 97 degrees (36.6 C) outside.
Observations: Sister's skin was the most sensitive. After 20 minutes her face and belly were red. The stripe of sunblock was clearly visible. The Cheeto stripe looked more like reverse freckles where the thicker specks of cheeto dust had been. Dad and Brother did not have significant coloring in that time, and only the faint line of sunblock was visible. (Brother almost didn't make it the 20 minutes in the sun. He summed up his the experience commenting, "I'm dying to death!")
Conclusion: Cheetos do not make good sunblock unless you like a pokadot tan. But they do make great treats as you are passing the time in the sun.
Update: As we were getting ready for bed we were again comparing outcomes. The color had set in with time, and we all had red bellies. All of us had a pronounced line where the SPF 50 sunblock had been, and a less pronounced spotty line where the cheetos had been. We were suprised how red we all were after just 20 minutes in the sun. So if you are at a picknic or at the pool and don't have sunblock, smear yourself in Cheetos. It is definitely better than being unprotected.