How Do Blacklights Make Things Glow? 💡

Henry Belcaster
Henry Belcaster
3 min read

Morning Durd!

1) Why are you in your bedroom in the opening graphic? That’s weird and not how we do this.

2) Why do you look like you’re hiding something from us?


Black light him.

Oh my god.

I had a feeling you had a problem after the ‘how do twins happen’ newsletter.

But we’re here to learn, not judge.

So how do blacklights make things glow?

Cause surely you’ve been there too.

You’re seal team 6-ing some friday night laser tag with your pals:

It’s smoky in there so you huddle up.

And right when you get under that black light, your team sees it.


That’s last month’s chili stains, your uncontrolled dandruff problem, and a huge pee mark from that time you were on a roadtrip and mom asked you eight times if you had to stop to go to the bathroom and you assured her you didn’t because you had a ‘steel bladder’ and then you had to prove that you did, in fact, have a steel bladder so you started chugging every last liquid in the car and then mom stopped asking if you needed to stop because she also wanted to prove that she knew you had to go the fourth time she asked so then it was a game of chicken for who would crack first and you wouldn’t dare let your mom be right so you just let a rip all over yourself.


So what’s going on?

Well black light is like any other light, but it mostly emits ultraviolet (UV) light.

A part of the electromagnetic spectrum our eyes aren’t tuned to see.

So we just see a faint, purplish glow.

Now most things a black light shines on stay dark.

But some stains glow super bright.

And that’s because those stains contain compounds called phosphors.

A thing that absorbs UV electromagnetic energy, then ~fluoresces~.

Basically it emits the energy it absorbed right back.

So when you shine a black light on a phosphor, you’re getting that object to convert invisible UV light into visible light we can see!

Highlighter ink, neon paint, human teeth, (and whatever Durd was doing in his bedroom) all contain natural phosphors!

Stay Cute,
Henry & Dylan 🌈

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