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Tweaks & Hacks

Turn Your Phone into a Black Light Hack

Black lights come in all shapes and sizes, and they’re useful in a variety of ways. They can help you spot fake currency, urine stains, interesting rocks, and deadly scorpions, and they can even help you view cool fluorescent artwork.

Most black lights work using a filter or coating over the bulb that filters out most of the visible light and produces mostly long-wave ultraviolet (UVA) light. Filters that do it create a dim violet glow, while coated bulbs product blue color. With a black light, you can see fluorescence, the radiating glow emitted by certain substances when exposed to ultraviolet light.

While no smartphone is technically capable of emitting UV light currently, you can mimic the effect of a black light using your phone’s LED flash, a few markers, and some transparent tape. It won’t work as well as a commercial LED black light, but if you’re just looking to show off some cool fluorescent art or mutant-looking plants, it’ll definitely do the trick.

Note: Black lights cannot help you see germs, bacteria, viruses, or proteins themselves. They can only highlight fluids and surfaces that contain fluorescence or fluorescent proteins. Whether those substances contain bacteria, viruses, or proteins is impossible to guess without proper lab gear such as a transmission electron or scanning electron microscopes. Some at-home microscopes can view bacteria at 400x or more, but viruses and proteins require higher magnification.

What You’ll Need

Image by Neil Gonzalez/Gadget Hacks

How to Turn Your Smartphone into a Black Light

The project can be be done in seconds if you have all of the materials in front of you. It’s that easy. And if you don’t plan on taking any photos or videos with your device’s camera, then feel free to tape over that part also — if you’re afraid of getting ink on your camera lens.

  1. Place a small piece of tape over the LED flash on the back of your iPhone or Android smartphone, which should be close to your rear camera. (It will also work on tablets with built-in flashes.)
  2. Color on top of the tape with a blue marker so that it covers the flash.
  3. Place another piece of tape over the flash, on top of the blue tape, and color it with the blue marker as well.
Image by Neil Gonzalez/Gadget Hacks
  1. Place a third and final piece of tape over the flash, on top of the blue ones, but this time, color over the flash with your purple marker.
Image by Neil Gonzalez/Gadget Hacks
  1. You’re done! Seriously, that’s it.

Using Your New Smartphone ‘Black Light’

On a piece of white paper, write or draw anything down with the highlighter, then turn on your device’s flashlight feature in a dark room and shine the purple/blue-tinted light at it.

Image by Neil Gonzalez/Gadget Hacks

The writing on the paper, in my case, yellow, will come to life thanks to your brand new DIY black light, giving it a prominent look in complete darkness.

Image by Neil Gonzalez/Gadget Hacks

Depending on the type of highlighter you use, your results will vary. Below are several examples, each from different highlighters, under my makeshift black light.

Image by Neil Gonzalez/Gadget Hacks

If you want to take photos with the black light on, just make sure that you don’t tape over the camera lens or lenses (like I did in my video up top), or you’ll have a pretty blurry picture. Likewise for videos, though, you’ll also want to keep tape off of your microphone, too.

Don’t Miss These Other Cool Fluorescent Hacks:

Just updated your iPhone? You’ll find new emoji, enhanced security, podcast transcripts, Apple Cash virtual numbers, and other useful features. There are even new additions hidden within Safari. Find out what’s new and changed on your iPhone with the iOS 17.4 update.

Cover image by Neil Gonzalez/Gadget Hacks



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