Turn Your Phone Into a Black Light Hack




About: We're a couple thats obsessed with all things geeky! And we make You Tube videos!

Turn Your Phone Into A Black Light Hack. Its super easy to do!

All it takes is a smartphone with a light, three pieces of small tape and two sharpies. One blue, one purple.

Take the first piece of tape, put it over the camera flash on the back of your phone. Color that tape blue. Repeat this step again. After you've put both layers of tape onto the flash or light of your camera, put the third and final layer on top of that one. This is where you pull out your purple Sharpie and paint that sucker in.

Things You Need:
-Smart Phone

-Scotch Tape

-Blue Sharpie

-Purple Sharpie

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Step 1:

Step 2:

Step 3:

Step 4:

Step 5: Turn Flashlight On

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    16 Discussions


    1 year ago on Step 5

    Hi, I have also determined that some phones are better than others.

    A good test is to see if the LED makes things fluoresce, notably blue/green EL wire or other nearby white LEDs. If so them this will work very well.

    If not then some phones let you increase flash power to 100% and there's actually a hack to boost it at the cost of LED lifetime, or even just replace the diode with a dedicated blacklight microLED and white phosphor external add-on array (cough SMD soldering is REALLY difficult and needs steady hands and 63/37 solder /cough) I've since found them for sale for about 60p a unit.


    2 years ago

    Thank You for posting this hack. I needed a cheap and easy solution to see which of my on hand materials would react under uv. This worked a treat, Thanks again.


    3 years ago

    I made this, I might've done it wrong because it didn't work. At all. I tried with just the torch on and I tried taking pictures with flash, nothing worked, it just looks like a cool filter on the flash rather than a "black light"/UV light. Damn.


    3 years ago

    Your not making a blacklight. A blacklight is a UV-A bulb. No cell can produce uv light. Your just making the led camera light cobalt. Blue light will make things fluoresce a little but, no where near what uv-a, uv-b, or uv-c bulb will. It's a waste of time. Just go buy a real blacklight blue UV-A light about 24 inches long. There like 15 bucks.


    4 years ago on Introduction

    You are basically making a "Wood's Glass" filter just like the glass on an incandescent Black Light, light bulb. It might work but not much power will be emitted at the ultraviolet wavelength from most white LEDs used for cell phone flashes. You need energy in the 100nm to 400nm wavelengths and most will be in the 300nm to 400nm.

    I'm going to give it a try, I'm betting finding the exact right the markers will make a pretty huge difference.


    4 years ago on Introduction

    Saw this on Facebook and doubted its validity, but I researched it anyways. First, in order for something to fluoresce, it needs to respond to UV light at the following wavelengths: Long-wave315-400nmLWUVA, Mid-wave
    280-315nm or Short-wave
    100-280nm. The graph below shows the emissions of a White LED used in a smartphone. 400nm and shorter (to the left), there are NO emissions. Hence no UV. Second, all that plastic tape would absorb UV light if there were any. Lastly, the odds of creating a UV bandpass filter with sharpies and scotch tape, pretty much don't exist. Not being mean, just stating the facts. The video "proof" was probably shot with a true UV lamp as the light source.

    The Manic Puppeteer

    4 years ago

    This is not a "black light". What you know as "black light" is ultraviolet light, which is unproducable with a standard camera flash. These operate within the visible light spectrum, which is far too low to emit UV. In addition to this, you are filtering out the blue band of the spectrum, not the violet (which would at the very least be closer). Check your information before submitting.

    1 reply

    In addition to this, the source of your pictures is dubious. They appear to be from an external source (and a poorly-informed one, at that).


    4 years ago on Introduction


    "Blacklight" is UV light, something not emitted at all by a phone's flash.

    All you are doing here is filtering out the red of the phone's white light, leaving the blue end of the spectrum. OK as a prop for cosplay or Hallowe'en, but it is not a working blacklight.

    I'm also very tempted to call "foul" on the still images, which had been around the web for months before you published the video.

    4 replies

    Reply 4 years ago on Introduction

    There are technically two common types of black lights. This one creates a light very similar to the "black lights" you buy at party stores.


    Reply 4 years ago on Introduction

    There's no "technically" about it. Blacklights emit UV, camera torches don't.

    Any comment on the provenance of the photos?


    Reply 4 years ago on Introduction

    I'm not looking to argue but feel free to google "Black Light" and types of black lights. You can see that I'm correct. As I mentioned above, this hack is similar to the blacklights you buy at Party Stores.


    Reply 4 years ago on Introduction

    A black light is a lamp that emits the longer end of the UV spectrum, but not much visible light. I don't need to google that, I know that, I'm a physicist, I teach this stuff.

    The long end of UV-A is around 400nm. The short end of a white LED's spectrum is about 25-30nm longer than the longest UV-A wavelength. See the attached spectrum - see the flat bit of the graph, with no emission? That's the UV-A part of the spectrum.

    All your "hack" does is cut the red end of the LED's spectrum, and leave the visible blue and violet end. A small number of phosphor-based dyes might fluoresce under the blue light, but you are not creating an actual black light. You are not adding UV to the emission spectrum of the LED, you are subtracting red from it. The only LEDs which emit UV light are UV LEDs, and they are not used in phones.

    It makes a fun bit of cosplay, but not an actual blacklight. Technosasquatch's comment shows clearly that the effect is not that of a true blacklight.

    I suppose one positive thing from this is that you removed the copyright-violating images and substituted your own, so well done for that, but fake projects like this, when presented as true, are not good for anybody, and could cause actual financial losses to somebody who relies on your hack to check the cash coming through their business. They certainly harm the learning of anybody who reads your hack before they are exposed to the facts in school.


    Might be good for a prop where you don't want unnecessary UV exposure.

    Try if for yourself, $5 and up bills have a security thread that fluoresces under UV.


    4 years ago on Introduction

    Wow! That works really well. Looks just like a black light. My phone took forever to load the video though :( Can you put up some more pics so that everyone can see how well your hack works?

    1 reply