How well does your favorite lotion protect against sunrays? Test suntan lotion to find out.
Sunscreen and tanning lotions screen out radiation. It's the UV (ultraviolet) waves in sunlight -- not the sun's heat -- that browns skin and can cause sunburn or skin cancer. Many people use sunscreen to prevent UV damage.
What You'll Need:
- Stiff cardboard
- Safe scissors
- Light-sensitive paper (such as Sunprint brand paper)
- Plastic wrap
- Various suncreens and tanning lotions
- Keys or other flat objects
- Paper clips
- Flat pan
To test sunscreen and tanning lotions, make testing frames from cardboard and plastic wrap. Cut a square of cardboard four inches wider and longer than the light-sensitive paper sheets. Cut a hole in the center of the cardboard the same size as the light-sensitive paper. Cover the hole with plastic wrap and tape in place. Cut a second square of cardboard the same size as the first to go under the frame.
Make as many testing frames as you need to test the various brands of lotion you have.
Put a dab of sunscreen on the plastic wrap of one frame. Spread it thinly and evenly over the entire surface.
Lay a sheet of light-sensitive paper in the middle of the solid cardboard square. Set a key or similar flat object in the middle of the paper, and cover with the testing frame. Paper clip the frame to the cardboard to hold everything together.
Set the stack in bright sunlight for exactly three minutes. Bring indoors. Remove the paper and soak it in a flat pan filled with water for exactly one minute. Let the paper dry completely.
Repeat the process with a clean frame for each lotion. Do one test using just the frame and no lotion at all for comparison. Which lotion worked best? Remember, the darker the paper, the more sunlight came through.
Learn more about how perspiration can cool you off on a hot, sunny day on the next page.