How does photoluminescent (glow in the dark) ink work

You can find photoluminescent products everywhere: from the stars adorning your childhood bedroom to the emergency exit signs in buildings.

These all owe their eerie glow to phosphors – a type of chemical that absorbs energy and re-emits it as visible light. Zinc sulphide and strontium aluminate are two of the most commonly used phosphors for photoluminescent ink as they re-emit energy over a long period. They can be mixed in with plastics or ink to create glow in the dark stars or prints.

When you shine light on a glow in the dark object, the incoming photons (packets of light) excite the phosphor molecules. These molecules release the energy they’ve stored slowly by giving out photons, creating a dim glow.

Different phosphors release energy at different rates – the slower they release energy, the longer they will glow.

Why is glow in the dark stuff green?

Glow in the dark pigments can be produced in many colours. The human eye is however most sensitive to green light, meaning that green glow in the dark stars appear brighter and so are generally favoured by manufacturers. This is also why night vision goggles typically colour things in green.

 

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