Measuring SPF Levels with UV Beads
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troublewithscience
- Posts: 1
- Joined: Sat Nov 08, 2008 7:29 pm
- Occupation: Student
- Project Question: Which sunscreen or sunblock is most effective?
- Project Due Date: 11/30/08
- Project Status: I am finished with my experiment and analyzing the data
Measuring SPF Levels with UV Beads
I ran an experiment testing the effectiveness of various sunblocks on UV beads. I chose the same brand of sunblock with various SPF's. The problem I am having is that all of the beads changed color so quickly so there wasn't much to measure. I used a scale of 1 to 5 and used a control bead that wasn't covered by sunblock, and ran the test 3 times. I'm in 7th grade and just don't feel like I've done enough of an experiment. Is there any other way to measure the effectiveness of the sunblocks using the UV beads?
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rmarz
- Expert
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Re: Measuring SPF Levels with UV Beads
Dear TroubleWithScience...
I hope your 'handle' hasn't made you cynical about the scientific method. Although I don't know much about UV beads, I did a little research and came to the conclusion that they are quite sensitive to UV exposure in a very short time interval. Many indicators and reagents in experiments react quite fast to stimulus, and perhaps your experiment allowed all test beads to effectively 'saturate' with UV radiation making it difficult to observe a differential between the various SPF level screens compared to the unprotected control sample. The experiment I read suggested that the various 'test' beads be allowed to dry after immersing them in the sunscreen, obviously in a UV free environment. Then the dried beads (and the control sample) would be exposed to about 10 seconds of UV radiation. If your method or time was different (longer) than this description, it would be like overexposing a sensitive photographic film to a light source beyond it's ability to be developed with a white-to-black gradient. In essence, it would be developed as black. It's possible that the beads were exposed well beyond their sensitive limit. If this example relates to your experience, perhaps you could rerun the experiment for a very short interval, then observe any change in a non UV lighted area, and if need be, re-expose them for a longer period until you saw some changes occur, especially in the non-protected control beads. You can always continue to re-expose them and get a cumulative absorbtion of UV radiation, but once overexposed, or 'cooked', no results will be observable. Perhaps some other experts that have had real experience with UV beads can add to this. Good luck.
Rick
I hope your 'handle' hasn't made you cynical about the scientific method. Although I don't know much about UV beads, I did a little research and came to the conclusion that they are quite sensitive to UV exposure in a very short time interval. Many indicators and reagents in experiments react quite fast to stimulus, and perhaps your experiment allowed all test beads to effectively 'saturate' with UV radiation making it difficult to observe a differential between the various SPF level screens compared to the unprotected control sample. The experiment I read suggested that the various 'test' beads be allowed to dry after immersing them in the sunscreen, obviously in a UV free environment. Then the dried beads (and the control sample) would be exposed to about 10 seconds of UV radiation. If your method or time was different (longer) than this description, it would be like overexposing a sensitive photographic film to a light source beyond it's ability to be developed with a white-to-black gradient. In essence, it would be developed as black. It's possible that the beads were exposed well beyond their sensitive limit. If this example relates to your experience, perhaps you could rerun the experiment for a very short interval, then observe any change in a non UV lighted area, and if need be, re-expose them for a longer period until you saw some changes occur, especially in the non-protected control beads. You can always continue to re-expose them and get a cumulative absorbtion of UV radiation, but once overexposed, or 'cooked', no results will be observable. Perhaps some other experts that have had real experience with UV beads can add to this. Good luck.
Rick