How to Make Invisible Ink


Introduction: How to Make Invisible Ink

About: One of humanity. Alike, but apart.

So I came upon this amazing formula for making an invisible ink , with could only be seen under UV/Black light.

Glad you asked!

Black lights are not that different from any other type of light, whether incandescent, fluorescent, or just the age old candle flame. The difference is that black lights emit most of their light waves just outside the range humans can perceive, in the Ultraviolet (UV) part of the spectrum. When a UV light wave hits an object containing substances known as phosphors, those phosphors will naturally fluoresce, and glow.

Phosphors are present in many daily use objects like Vaseline, tooth whiteners, body fluid (you know, the gross ones...), bank notes, laundry detergent etc.
So, when you know, let's start.

Step 1: Stuff Needed

Get :
A Highlighter (Any, really, absolutely any)
Hot Water
Empty Cup
A UV/ black light
A Water tight Jar.

Step 2: Take It Out

Depending on what kind of highlighter you have you can usually open them up with pliers. Don't destroy the highlighter trying to get it open. Once you get it open take out the tube of ink that is inside, and pull the tip (the part you write with) out of it with pliers.

Step 3: Microwave

Put the tube and tip into a cup of water. Put it in the microwave until it starts boiling.

Step 4: Into the Water!

Take out the tube with the pliers and squeeze all of the ink out into the cup. Do the same thing with the tip.

Step 5: Fin!

Add enough water so that you can see through the water clearly but it is still dark. Put the tube and tip back into the cup and put it in the microwave until it boils again.

Step 6:

Put the parts back into the highlighter and you have your invisible pen! Dip the pen into the ink and write with it! To save the ink put it in a water tight jar so you can refill your pen. Your ink will show up under a UV light or black light.

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2 People Made This Project!


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21 Discussions

how much water do you use?

Nope, didnt work for me either. Tried different brands and colours of highlighters. By the time the stuff is dilute enough not to be seen in day light, it doesnt show up under UV either. If its strong enough to show up under UV, it can be seen in daylight....It could possibly be that the UV im using is in the 390 - 405 nm band. It may work with shorter wave UV......

However, whilst doing the experimenting, i've found something in the kitchen that glows wonderfully, well, I found many things actually, but trying to narrow it down to something that wont go/isn't rancid, and is water soluble and kiddie safe. Once dried, my coffee seems to glow a nice sickly green yellow, probably the milk and sugar...but dont fancy the likely smell of the pen/ink after a day or so....

Is this toxic or unsafe by any means (excluding eating it, of course)? because I don't want to put something on my skin and then it ends up burning and giving me a rash.

1 reply

Its Fine I Have it All Over My Hand

It is a cool idea and I am going to get mine out right now and try it ,I like this idea and I made it

I didnt work.
No matter how I try.
I really need help.

Worked great - thank you!

Just to be clear, if I go down to Walmart and buy a Halloween black light-bulb, would that work? I've tried another set of "Halloween black lights" and they didn't seem to make the ink show up. Thanks!

2 replies

use any flashlight with blue marker pen and tape(like on this video - )

I tried this and I love it! It works perfectly. Thank you so much for coming to my rescue! I am making a huge project, that is becoming very costly and I found this website and am totally stuck on it! I will try and post my pics when the project is completed. Once again, thank you for sharing your brilliance!

I'm guessing it was diluted so that it would appear invisible. Visible highlighters would show under a black light (guessing) but wouldn't be invisible. Did you try it with the dollar store highlighters?

That cover image belongs to you? That's unlikely. A reverse image search shows it going around the internet for years along with articles around blacklight tattoos.

Here's one from 6 years ago.

1 reply

Okay, well.
My brother is an artist living in Nevada. He is, coincidentally, a tattoo artist. He did the image above for his store a decade ago. I used the image with his permission.


3 years ago

So, are you actually watering down the highlighter ink, so that it is only visible under UV light? Nothing special added?

And second, could you simply pour boiling water over the pieces, rather than nuking them? Just curious if I could avoid microwaving those items ;)

Lastly, looks awesome and I am going to pick up some dollar store highlighters and give this a go. I think zentangling with this ink, on a larger scale, could be a whole lot of fun XD

1 reply

No, nothing special added. ;)

I don't really know that, cuz i didn't try that. Maybe you could make 2 batches and tell me what worked better?

Thanks, means a lot.
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