Science Buddies: "Ask an Expert"

I am considering to a science fair project testing the effectiveness of different levels of spf in sunscreens. My problem is coming up with the proper medium on which to test the sunscreens. One book suggested using newspaper as ultraviolet light turns newspaper yellow.

Can anyone tell me why UV light turns newspaper yellow? Without knowing this I don't think it makes sense to use newspaper in the experiment. Any other ideas for mediums that I could use?

Thanks

mcdomzal wrote:I am considering to a science fair project testing the effectiveness of different levels of spf in sunscreens. My problem is coming up with the proper medium on which to test the sunscreens. One book suggested using newspaper as ultraviolet light turns newspaper yellow.

Can anyone tell me why UV light turns newspaper yellow? Without knowing this I don't think it makes sense to use newspaper in the experiment. Any other ideas for mediums that I could use?

Thanks

Hello, mcdomzal!

I love your choice of projects. This is a very interesting area of investigation.

Light damage to documents is an issue of high concern for libraries and other institutions that are interested in preserving documents - most of which are printed on paper. Doing some research for how documents are protected and preserved will probably yield an answer for what happens to newspaper and why it happens.

You might also consider running a quick experiment of your own right now just to see. For example, you could place two pieces of newspaper in a sunny window, covering one with a thick cloth or piece of cardboard. The covered piece would be your control. Periodically you could compare the color of the samples to get some idea of how long it will take for your experiment to run.

Have fun with this project!

McDomzal:

My son did a variation on this exact science fair project last year. Your question is an excellent one, as he spend a large amount of time finding materials that don't transmit ultraviolet light, while really searching for ones that transmitted almost all the ultraviolet light.

Much to his dismay, he learned that many transparent materials absorb much if not all ultraviolet light. We were able to discover this because a friend was an optician who had a device that measured UV transmission through sunglasses. Perhaps you could find a local optician who could help you out to find/test materials.

Finding a suitable material will likely be one of your hardest tasks. But when the lightbulb goes off, you will find some household items that are perfect. That's as big a hint as I will give you.

You could also do a google or ask.com search on different materials and look up their UV transmission rates. This will provide you with some information as to which type of glasses might work for you, and which wouldn't. There is a government organization in the US that tests sunscreens. You can also learn a lot of useful information by searching their website once you learn who does that.

The UV testing equipment was rather expensive, which you also might want to consider before embarking on this project. We also got considerable sunburns while doing the tests, so don't forget to put the best sunscreen on yourself before doing the experiment. Your safety is what's most important.

Good luck with your project. It is a complicated one, with many unseen pitfalls, but will also provide you with some unexpected results. Always a good outcome in a science project