Turn your phone into a black light

Martyn Casserly reveals how to transform your smartphone’s flash into a black light

Black lights can be a lot of fun, causing teeth, white clothes, and neon colours into glow-inthe-dark. They’ll give your party a seventies or nineties (depending on your age) feel, and the

kids will be mightily impressed. It’s incredibly easy to make a black light with your phone and we’ll show you how.

What you’ll need

The requirements for this particular project are very minimal. You’ll obviously need a smartphone with a flashlight capability (pretty much every one built in the last few years), some clear tape, plus blue and purple markers. You might also want some highlighter pens to create artwork that the black light can bring to life. We found yellow, pink, and orange worked the best.

Creating the Black Light

Take a small strip of clear sticky tape and place it over the flashlight LED on the back of your phone. Now gently colour the area directly above the LED blue. Place another piece of tape over the first one, being careful not to smudge the ink. Repeat the first step but this time using the purple marker. Now do the same thing again, alternating between the blue and purple colours.

With those layers complete your Black Light is ready to test. Try drawing a simple pattern with your highlighter pens or writing a message on some plain white card. Then hold the phone above your work and turn on the flashlight.

‘What is this sorcery?’ we hear you cry, but fear not. Your phone now has UV-A light emitting from its flash and not much else. This means fluorescent colours will leap out whenever you shine your light upon them, and you could probably take some very weird low-light photographs.