How to use sunlight to paint a picture

AUSTIN, Texas - This experiment is a fun, colorful way to illustrate how sunlight heats up different colored surfaces differently. 

Here’s what you’ll need:

• One black poster board or foam board
• One white poster board or foam board
• Two boxes of crayons
• Superglue
• A little patience, this experiment takes a few hours

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To start, you’ll superglue one box of crayons to each poster board. After the glue has a moment to dry, you’re ready to go outside.

Find a place for the poster boards where they’ll be in full sun for a few hours. I did the experiment on an afternoon where the daytime high warmed to 88 degrees.

Place the posters side-by-side and wait.

After about 4 hours in the sun, the crayons on the black poster will have melted much more than those on the white poster board. 

Here’s the science behind it: When the sun’s rays hit a surface, some of the rays are absorbed and some are reflected. The color our eyes see are the rays that are reflected. Black surfaces absorb all of the sun’s rays while white surfaces reflect all the sun’s rays. 

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But where do the rays go when they’re absorbed?

In this case, they’ve turned from light energy to heat energy.

Since the black poster board absorbs more of the sun’s rays, it has more light energy to turn into heat. This resulted in the black poster getting hotter than the white poster, something we can see by how the crayons melted.

This is also why you hear meteorologists encouraging people to wear lighter colored clothing on hot days. They’ll help you stay a little cooler!