Sunblock Studies

Finally the sun is out and we can do our sunblock experiments!  Let me back up for a second.  The family was watching ‘Sid the Science Kid’ on PBS a few weeks ago and on the show they did an experiment with sunblock.  The kids were intrigued and wanted to do it themselves so we got the materials together and waited for a sunny day that we were free in the afternoon to do our experiment.  That was 3 weeks ago.   The anticipation of our sunblock experiment day is so high at this point that I hope the kids have as much fun as they are expecting.

On ‘Sid’ the teacher had the kids fingerpaint a colored piece of paper with sunblock and leave it out in the sun to see how the sunblocked part of the paper doesn’t fade like the rest of the paper in the sun.  I think that there should have been a control – a paper left inside to see the color change that the sun caused.  I also think that there was a great opportunity to talk about SPF and explain how sunblock works that was totally missed by this episode.  That being said, I still think it’s a good experiment – but I tweaked it a bit to make for a more informative experiment for my girls.

I start by explaining why we wear sunblock to the kids.  I tell them that sunblock makes most of the ultraviolet (UV) and visible light that hits us either bounce off or turn into heat.  We don’t want too much sunlight to hit our skin or it will burn us and that hurts.  I want to tell them that too much sun can cause skin cancer but I decide not to because I don’t want them to be scared to go outside either.

As an aside for my readers with older kids, the full story of sunblock, such as I understand it, is this –

Sunblock contains 2 types of ingredients, inorganic and organic.  The inorganic ingredients, usually zinc oxide or titanium oxide, reflect UV radiation.  The organic ingredients, usually octyl methoxycinnamate or oxybenzone, absorb the UV rays and dissipate them as heat.

While there are UV-A, UV-B, and UV-C rays, the SPF on your sunblock is a measure only of how well the sunblock gets rid of the UV-B rays.  UV-C  rays are absorbed by the atmosphere so they don’t reach our skin in natural ways.  If you are concerned with UV-A rays, which penetrate deeper than UV-B rays, and also can penetrate glass which UV-B rays can't (think sitting in your solarium), make sure your sunblock has the words “broad spectrum protection” or “UVA/UVB protection” or something to that effect on it.

I also tell the kids that each sunblock has an SPF number written on it.  SPF means sun protection factor.  I stop to let that information soak in because I want them to take away that when they see SPF on things it means how much it will protect you from the sun.  So I ask the kids, “What letter does sssssun begin with?” and when Briana says “S!” I write a big S on the kids’ chalkboard.  Then I ask about ppppprotection and fffffactor.  We’re left with the letters S-P-F written on the chalkboard.  Then I grab one of the sunblocks that we are going to use in our experiment and tell Briana to find the SPF label on the bottle.  She’s super happy to have “read the bottle all by myself”.  I show them that all of the sunblocks that we have out have numbers after the SPF and the bottle with the biggest number has the most blocking power.

A second aside -  Technically SPF is a measure of how much solar energy or UV rays it takes to sunburn the skin with that sunblock on it relative to the amount of UV rays it would take to sunburn skin with no sunblock on it.  SPF is not related to time.  I’ve heard people say that SPF 30 means you can stay out 30 times longer than you could without sunblock or twice as long as you can with SPF 15.  Not true according to the FDA.  SPF is a measure of amount of rays you can withstand, not how long you can withstand them.  They measure SPF this way because measuring based on time would be dependent on other variables like the intensity of the sun, which varies based on time of day and your location (ie. Texas versus Alaska).

Then I tell the kids that the FDA just said that any suncreen over SPF 50 doesn’t protect you significantly more than SPF 50 does.  We’re going to run our own experiment to see if the higher the SPF the better the protection.

We grab our supplies and head out to the deck-

1)   3 sunblocks – SPF 30, 50, and 110

2)   5 pages each of 2 colors (yellow and red) of construction paper

I give Briana the SPF 50, Abby gets the SPF 30, and I get the 110.  Why?  The SPF 30 that I had is in packet form so Abby wouldn’t get a whole bottle to make a giant mess with.  The 110 is a spray, which is better if I use so no one sunblocks their own or anyone else’s eye.  I know it’s bad experimentation to include form (spray vs. liquid) and amount applied as variables, but I did it anyway.

  

I try to make sure that the kids leave some of the paper unsunblocked so we can compare.

We each put our assigned sunblock on one sheet of red and one sheet of yellow paper each.  I label each paper with the SPF of the sunblock that went on it.  One of the 2 remaining sheets of paper in each color is left inside as a control.  The other sheet I write “mystery” on and I sunblock it with one of 3 options while the kids close their eyes.  We’re going to see if we can tell which sunblock is on the mystery sheet by how it looks after an afternoon in the sun.

We lay the sheets out on the deck bench, anchored by some rocks.

  

Then it’s naptime for the girls.  The sun can do its job while they sleep.  Since the girls tend to take 3-4 hour naps, by the time we get back outside we should be able to examine our papers to see the effects of the sun.

When the kids get up, and snacked, we head outside to examine our papers.

I took pictures of the sheets next to the control, but it kind-of all looks the same in the pictures.  In real life, however, you could easily tell the difference between which sheets had been inside and which had been outside.  Bree was really surprised by how much the sun faded the paper.  She insists, “I need to put on sunblock now, Mommy, so I don’t fade out here.”  I tell her that when the sun breaks down the color pigments on the paper it looks faded.  When the sun breaks down our skin, it burns and then our skin repairs and protects itself by adding extra melanin, which makes it look darker for a short time afterwards.  So when our skin gets too much sun it gets darker.  The word for that is “tan”. 

We looked at the yellow and red papers and noticed that the red paper faded more than the yellow paper.  Briana decides that, “the brighter the paper, the more that it fades.”  A great observation.  She also observes that “the sunblock soaked right through the paper even though we just put it on the top part”.

We also looked at the color of the spots on paper with the different sunblocks.  They all looked the same.  We conclude* that “it doesn’t matter what SPF you have on as long as you have some sunblock on”.  *This statement has not been evaluated by the FDA, who would likely not find this experiment scientifically sound.  Since they all looked the same, there was no way to guess at our mystery paper.  Too bad.

Before we stop thinking about sunblock, we talk about how to apply sunblock.  I tell them that there are 3 rules: 

1)   Put it all over your body – don’t forget your face or ears or toes.  Everywhere needs sunblock.  Briana amends this to say “Except your eyes.  No sunblock in my pretty eyes.”

2)   Put it on 30 minutes before going out so it can soak in and you won’t sweat it out as quickly.

3)   You have to put it on again after swimming, even if it says waterproof.  If you aren’t swimming you need to put more on every 2 hours.

The kids happily (for once!) cover themselves with sunblock, and then we go inside, put on our bathing suits, and head to the pool to enjoy the sunshine…safely.

Did you absorb all of that info?  I think blogging is making me way too into the pun - try not to burn me for it. J

<3 Pedigreed Housewife