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Title: Do Different SPF's Make A Difference When Using Same
Brand Sunblock? Does Price Affect The Way Sunblock

Grade: 7

I. Statement of Purpose and Hypothesis:

I wanted to know if SPF matters when you buy sun block. For
example, does a CVS brand 30 sunblock work better than a CVS
brand 15 sunblock? I also wanted to know if higher priced
sunblock works better than lower priced sunblock of the same
SPF? My hypothesis was that the higher the SPF the better it
would protect and that higher priced sun block would work better
than lower priced.

II. Methodology:

For the first part of my project, I bought four types of CVS
brand sunblock. Each of these sunblocks had a different SPF.
The different SPF's were 30, 15, 8, and 4. I also bought a pack
of developing paper at a local photography store and 4 clear
plastic report folders. I then got some distilled water and a
dish pan. I asked my science teacher for sodium thiosulfate.
The first thing I did was divide the report folder in 4 equal
squares using masking tape. I then labeled each sun block 1, 2,
3, or 4. I labeled each square 1, 2, 3, or 4. I then applied
the numbered sunblock to the appropriate square. I put the same
amount of sunblock on each square making it as even as possible.
After I put the sunblock on, I dimmed the lights very low. I
carefully took out a piece of developing paper, making sure to
close the case afterwards to keep the light away from the other
sheets. I put the developing paper, glossy side up, inside the
report. I then quickly took it outside on the driveway where it
was very sunny. I left it there for exactly 5 minutes. While
it was in the sun I made the mixture of the sodium thiosulfate
and distilled water in the dish pan. When the 5 minutes was up
I brought the report folder back inside to the semi-darkened
room. There I carefully took out the developing paper from the
report folder and layed it glossy side down in the mixture for
three seconds. Then I immediately rinsed it with cold water and
let it dry for 15 minutes. When it was dry I observed it.
For the second part of my experiment I did the exact same thing
except I used the sun blocks that varied in price, but had the
same SPF.

III. Analysis of Data:

On the developing paper, the sunblock which allowed the least
amount of sun to penetrate, turned the whitest. When I observed
the data from my first experiment I was very surprised at what I
saw. I noticed that the SPF 30 sunblock was darker than the SPF
4 sunblock. This was very strange because I surely thought that
30 was better than 4. What I then saw was that in some places I
had put more sunblock on the number 4 square than others, also
the places where I had put more sunblock were the lightest and
where I hadn't put much on it was the darkest. For trial one
SPF 4 was the best, then SPF 8, then SPF 15, and last SPF 30.
For trial two, SPF 8 was the best, then SPF 4, then SPF 15, and
last SPF 30.

For the second part of the project my results were not as
strange, but were not what I expected. For trial one, "Bain de
Soliel", which was the highest priced, worked the best. "Banana
Boat", which was the least expensive, was second. "Bio Sun",
the second highest priced was next, and then the second lowest
priced, "Neutrogena" came in last.

IV. Summary and Conclusion:

I was very surprised when I saw the results of
both tests. They did not agree with my hypothesis at all. For
the first experiment, it seemed to me that it did not matter
what SPF you used, but how much you put of each one. That is
why I think SPF is irrelevant, if you put a lot of sunblock on
and keep reapplying it.

For my second experiment, I think it mattered how thick the
sunblock was. Bain de Soliel was the thickest and then Banana
Boat. But Neutrogena which came last was not thick and was very
light. So, for my second experiment, I feel price does not
matter, but thickness does.

V. Application:

I can apply the results of this experiment in many ways to my
life now. I now know I can use any type of sunblock and the SPF
will not matter. I will just have to remember to put a lot on
and keep reapplying it. I also know that if I buy a sunblock
and it has a thin texture to find another brand. These results
can be critical for many people. With the depletion of our
ozone layer, skin cancer is a common problem. People need to be
aware of the SPF confusion and be informed about thick
application of sunblock to prevent the damaging effects of the