Sunscreen SPF Test

School’s out and summer is just around the corner, which means tons of outdoor fun! Celebrate National Safety Month by taking a look at how you can keep your skin safe from the harmful effects of the sun. What SPF sunscreen really works to keep out those harmful UV rays?

Materials

• Various strength sunscreens (i.e., SPF 15, SPF 30 & SPF 70)
• One lotion with no sunscreen
• Squares of black construction paper
• Scissors
• Pen
• Coins
• A sunny day!

Activity

1. Set aside one paper square and apply the lotion with no sunscreen. This will be your “experimental control” or point of reference.
2. Coat the other squares of black construction paper with sunscreen, and rub into the paper until the sunscreen is absorbed. Make sure to label each square with which SPF you’ve applied!
3. Place the paper squares outside in direct sunlight and weigh them down with coins.
4. Repeat steps 1 – 3 with a second set of papers and place them indoors under regular light.
5. Leave the papers outside in the sun for at least a few hours (recommended = 5). To increase the effect, collect the papers at the end of the day and place them in the sun again the next day.
6. At the end of the day, compare your squares to the “fade-o-meter” to determine how much they’ve faded.

Explanation

The electromagnetic (EM) spectrum describes different types of light. Light is referred to as an EM wave because it is made up of both electric and magnetic waves moving together through space. The EM spectrum is arranged by wavelength with longer wavelengths to the left, shorter wavelengths to the right. We are most familiar with visible light and all EM waves in the spectrum are types of light. Did you know x-rays were a type of light?

Our eyes can only see the small portion of the EM spectrum called “visible light” which includes all the colors of the rainbow. Everything else in the spectrum is invisible to our eyes. For example, ultraviolet (UV) light is a part of the spectrum we humans cannot see, but other animals can see UV light, including bees, butterflies, and reindeer.. UV light has a smaller wavelength than visible light, which is why it is to the right of visible light. Other types of light we cannot see include radio waves, X-rays and microwaves.

Though we cannot see UV light, we can detect it in other ways. One way is sunburn! When your skin turns red from sitting in the sun, it is detecting the presence of UV rays. It also hurts! What are some ways we detect radio waves? How about X-rays?

Explore the EM spectrum in the Waves room in Space Chase with our new and improved Space Imaging exhibit!