The diversity of skin types in Homo sapiens gives rise to a wide variety of responses to exposure to sunlight. This study aims to investigate the responses of a particular specimen, a 21-year-old female named Kate, whose sensitivity is distressingly binary. The vast majority of her existence is spent with an extremely pale skin tone. However, after a certain threshold of sun exposure, she becomes violently, painfully bright red. The anecdotal evidence of her history of sun exposure does not include any episodes where she can be described as the desirable “tan” – it’s albino or lobster for Kate.
The purpose of this study is to characterize the point at which the specimen switches from pale to burned, and to methodically determine if there’s any window for her to be tan in between. The study was prompted by the novel situation of being in sunny California for an entire summer, and also partially by being bored on a Sunday afternoon. By investigating a variety of circumstances under which tanning might occur via natural sunlight (no tanning salons!) the goal is to understand Kate’s skin’s sensitivity, and by the end of the summer, somehow engineer a tan.
The experiment took place by the pool of the Stanford Park Hotel, between about 1 pm and 3 pm on Sunday, June 16th. The subject was exposed to sun and shade in alternating 15-minute intervals. A smartphone was used as a timer. After each fifteen minutes, she switched between the lounge chair on the sunny side of the pool and the lounge chair in the dappled shade on the other side of the pool. The experiment lasted for 4 sun periods (a total of 1 hour) and 3 shade periods.
The temperature was about 70 degrees, and there was no wind in the shelter of the hotel courtyard, so it felt frickin hot! The sun was almost directly overhead. There were no clouds whatsoever. The weather record for that afternoon can be found on this shiny site: http://weatherspark.com/#!dashboard;a=USA/CA/Menlo_Park
The subject was provided with 40-inch size 1 circular knitting needles and 100g of Three Irish Girls McClellan Fingering (30% bamboo!) in the colorway Pixie Hollow, because sitting around by the pool would be boring if she didn’t have socks to knit. The subject was also provided with Cherry Coke. Duh.
Attire was shorts and a t-shirt. The subject did not turn because lying on her stomach sounded boring and she wouldn’t have been able to knit. While the subject’s face, arms, and legs were exposed to the sunlight, only the legs’ sensitivity was measured. Measurements were taken by photographing the subject’s legs three times during each sun period: at the beginning, about halfway through (this was not very consistent), and at the end. The photos were all taken on the sunny side of the pool to attempt to control the lighting. One shady-side picture was taken to show the dappled nature of the shade:
Against all her instincts born of a lifetime of dealing with painful sunburns, the subject did not wear any sunscreen whatsoever. These are the sacrifices you make for science.
(Okay, abandoning the third person thing because it’s getting awkward.)
The sun is really hot when you’re sitting in it on purpose. Usually when I get a sunburn I’m out playing, on the boat or somewhere else, doing something to keep my mind off how hot it is. This methodical business, by contrast, tends to focus me in on how hot it is.
I should have done this in a bikini–I will probably have an awkward shorts tan after this afternoon.
And one final data point: as I write this, the tops of my thighs hurt as though they are burned. Aaand… yes, I have a burn line where my shorts were:
I believe I just spent two hours methodically getting a sunburn.
It’s possible that sunburn only appears a while after you sit in the sun – even if you get out of the sun, it takes some time for the burn to appear. Anecdotally, this seems about right. However, it’s a harder theory to test – in order to have the duration in the sun as a variable, I’d have to spend multiple different days testing different amount of sun exposure before I get out of the sun and wait to see if a burn develops. This would present the problem of recovery time, too: suppose I burn myself in one trial. Obviously my next trial should be shorter, but how long do I need to wait for my burn to heal before trying again, to be sure that it won’t affect later trials?
Another possibility would be dipping in the pool every 15 minutes when I switch – and this would probably make it more comfortable. It would cool off my skin temperature, but would this affect the UV exposure, and eventually the color/tan-ness/burned-ness of my skin? This is also a more relevant test to engineering a way for me to get tan in real life, because most of my sunshine activity involves swimming or boating in some way.
Then, there are the obvious questions to answer. What if, instead of 15 minutes off, 15 minutes on, I went with a different schedule? 20 minutes on and 10 minute off? A longer or shorter period than 30 minutes?
The entire experiment is also victim to issues of controlling all the variables. I can control for things like the time of day, and probably even cloudiness, but I have a feeling that things like temperature have a pretty big effect, and I can’t control the temperature (that is, if I want to stick to only natural sunlight, which I do.) I’ll have to accept simply recording the temperature for all my data and trying to draw conclusions that way.
What if different parts of my skin tan differently? While I’m pretty sure at this point, given the pain they’re in, that my thighs are burned, and my face doesn’t feel so great either, my arms feel totally fine. As far as I know they were in just as much sunlight as my legs, so perhaps the skin there has different sensitivity? It would be interesting to investigate the relative sensitivity of my legs, arms, face, belly, etc. One possible application of this would be learning which parts need the most sunscreen or most frequent reapplication.
Speaking of sunscreen… how do different brands and SPF rating of sunscreen affect the tan (okay, time to stop kidding myself, burn) I eventually get? There are so many variable to investigate here: how long before sun exposure do I apply, when do I allow myself to get in the water, reapplication timing. And that’s not to mention all the brands, strengths, application methods (spray-on, aerosol, lotion), etc. (I’m kind of experienced at sunscreen.) In the other direction, they make tanning oil I could try—but I think I know better than that. It would be so fun to paint myself in stripes of different brands/strengths of sunscreen and see what happened. It would also be very dorky-looking the next day. Oh well. For science!