What Are Glow-in-the-Dark Crayons?


Quick Answer

Glow-in-the-dark crayons glow because a substance known as phosphor is added to them when they are manufactured. Phosphor possesses photoluminesce, which means that when energized, it can radiate visible light.

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Full Answer

The two most common phosphors are zinc sulphide and strontium aluminate; of the two, strontium aluminate is the stronger phosphor. To be able to glow, the crayons must first be energized or charged. As with most glow-in-the-dark toys, charging can be done by shining a light on the crayons for a few moments. Stored within the phosphor molecules, the photons of light release at a slower rate than when originally charged.

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