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So we recently purchased a subscription to TheHappyScientist.com and we’re loving it (and the subscription was cheap!)
TheHappyScientist.com is full of short videos with all kinds of neat, simple science experiments that don’t require any special (read: expensive) items. We watched a video about making sun prints last week and we decided to take it a step further and test out the sunscreens we have around the house. Which one would provide the best protection?
To perform this experiment you need the following:
-a piece of brightly colored construction paper
-a large piece of glass (a cheap photo frame works well, ensure your glass doesn’t have a protective coating)
-a dry erase marker
-a solid control object
-several different types of sunscreen (we live in Florida ergo we have a lot!)
-a sunny day
Place the construction paper under the glass.
Use the dry erase marker to mark off 1 square for each sunscreen and 1 more for the control.
Place the control object in the first square, as you can see we used a seashell.
Apply sunscreen to the other squares. This is hard to get exact but don’t stress out over it! It’s equally difficult to apply sunscreen evenly on a person, it doesn’t have to be perfect.
Place the entire experiment in a sunny spot. I put a cork placemat under ours so it would be easier to carry.
Check the experiment in 30 minutes to get early results, just be careful not to dislodge the control object or smear the sunscreens.
When 2 hours have passed collect up the experiment and bring it inside. Allow your eyes some time to adjust to the indoor lighting, place the construction paper under a bright light and analyze your results.
(It proved very difficult to get a photo that is as good as the real thing. Some of the blotches here look a little lighter than they do in real life, what follows is our analysis based on viewing the paper in real life)
#1 – Sunglasses – This was a lens from a cheap pair of kid sunglasses purchased for less than $5
#5 – Neutrogena Ultra Sheer Dry-Touch Sunblock with Helioplex, SPF 70
Active ingredients: Avobenzone 3%, Homosalate 15%, Octisalate 5%, Octocrylene 2.8%, Oxybenzone 6%
#2 – Banana Boat Kid’s Sunblock Lotion, SPF 50
Active ingredients: Homosalate 15%, Octinoxate 7.5%, Octisalate 5%, Titanium Dioxide 2.4%
#4 – Ocean Potion Face, Clear Zinc Oxide, SPF 45 — 1 fl oz
Octinoxate 7.5, Zinc Oxide 7%, Octisalate 5%, Octocrylene 2%
#6 – Ocean Potion Suncare Cool Dry Touch Sport, SPF 50 (ours was sold under the Margaritaville Floridays name)
Active ingredients: Homosalate 15%, Octisalate 5%, Octocrylene 7%, Avobenzone 3%
#7 – Coppertone Ultra Guard Broad Spectrum SPF 50
Active ingredients: Avobenzone 3%, Homosalate 13%, Octisalate 5%, Octocrylene 7%, Oxybenzone 4%
#3 – Nivea Invisible Protection Broad Spectrum Transparent Spray, 50 SPF. (This product is only available in the UK, I had a friend ship it to me in my quest to find the perfect sunscreen)
Active ingredients not listed.
How this experiment works:
Construction paper gets its color from something called pigment. Pigment is also present in our skin, it’s what colors our skin and gives us freckles.
The sun produces all kinds of crazy energy, and one of the kinds we know the most about is ultraviolet light. This type of energy is responsible for discoloring the construction paper, and also for giving us sunburns! To learn more about what ultraviolet light is check out this cool link.
Just like the control object blocks the sun’s rays, so does sunscreen. All sunscreens provide basic sun protection but they each vary in how much of the sun’s rays they block and for how long. Each type of sunscreen is made from different ingredients and some just work better than others.
Ways to expand this experiment:
-Compare different sunglass lenses
-What happens if you reapply the sunscreen every hour?
-Try this on a cloudy day
-Try using traditional, natural sunscreens (mud, coconut oil, etc.)
-What can you do to make the results more reliable?