Have you ever wanted to get one of those cool invisible ink pens from the store so you can write secret messages to your friends? Or maybe you need to use it to mark peoples hands for admission to a party. With this Instructable, you can easily do so, and do it for only 25¢!!

Step 1: Gather The Materials

There are very few materials needed for this Intstructable. These are listed below:

1 Highlighter (I got a pack of 4 different colors for only $1)
1 cup (plastic works best, so you don't have to worry about washing it out)
3 Tablespoons hot water
cotton swab

Step 2: Take Apart the Highlighter

-If you want to make the pen, be sure not to lose or break any parts.
Start by taking the cap off. set aside.
Using the pliers, grab and pull of the front plastic piece of the marker.
Next, slide the ink cartridge out of the back of the marker.
Then, also using the pliers, pull the tip of the marker out.

Step 3: Extract the Ink

This step is not hard at all.
Place the foam ink cartridge and marker tip in the plastic cup
Poor the 3 tablespoons of hot water over the cartridge
Let the ink cartridge soak for about 5 minutes
Squeeze all excess ink from the cartridge, then let soak a little more. repeat until the cartridge is a light color, and the water is dark.

Step 4: Test the Ink

Using a cotton swab, dip one end into the ink.
tap all excess ink off.
write something on your arm. I did a G for green.
if it you can see it on your arm, then you didn't get enough off the excess ink off. just dab the excess off your arm, and it will be fine.
Go into a dark room, turn on a black light, and watch the message glow!

From this point, you can use the ink for what you want; stamps, cotton swabs, fingers, etc.
Keep reading to see how to make the pen!

Step 5: Making the Pen

Take the Ink Cartridge from earlier, and squeeze it so that excess ink comes out. IT DOES NOT NEED TO BE DRY, JUST DAMP. You should be able to squeeze some out if you try hard.
Re-assemble the pen.
Start with marker tip, and slide it back into place.
Then, put the cartridge into the front part.
push the front piece onto the back piece.
put the cap on.

To use, write with it. to view, look at with UV light.

if you can see the marker when you write, then you need to squeeze more ink out of it.
If the marker isn't writing, then you need more ink in it.

Step 6: Storing the ink

To store the ink, poor into a small, watertight container. BE SURE ITS WATERTIGHT, UNLESS YOU WANT INK ALL OVER YOUR CARPET. I used a medicine bottle. Also, it might be a good idea to label it.

After your marker stops writing, simply soak it in the ink for a little more, and squeeze the excess out!

Step 7: Other Tips

the ink works best on skin
Don't where white clothes, and do it somewhere where you can wipe the ink up it it spills.
need a black-light? Home-Depot sells some Eco-bulbs for around $6, Walmart sells a lamp for around $10, and Amazon has a Chauvet Handheld Black light for around $6.
I have 2 of the lamps, one of the bulbs, and one of the handheld ones :) They all work great, especially for the price.

<p>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 &quot;Halloween black lights&quot; and they didn't seem to make the ink show up. Thanks!</p>
Make sure you use yellow!
How long does the ink last? And can you change its color?
<p>It lasts until you wash it off, it will not lose its glowing ability. To get a different color just use a different highlighter</p>
<p>How do you recommend storing the ink?</p>
<p>How much water do you need if you are using one of those thick highlighters, and not those thin ones? </p><p>Also, to make it better adapted to writing on paper, it helps to put in a few drops of dish soap.</p>
How long does the ink last? And can you change its color?
Very interesting!
<p><strong>I</strong> <strong>totally agree!</strong></p>
<p>can it work without uv, and would it work in a normal room instead of dark room?</p>
Can we take a marker instead of highlighter ???????<br> If not then can we use the other highlighter its a little bit fat....<br><br>Please answer and thnks in advance :)
<p>It only works with highlighters because of the neon color. But I suppose if the marker is neon it might would work. And yes, any highlighter will work, it doesnt matter the thickness</p>
why do you have one sock on and one sock off?
theres a black light leds, I would put one of those leds in a lighter so it wouldnt look that suspicious, it would be less bright but more stealthy.<br><br>heres a list of fuluorescent stuff by wikipedia<br><br>laundry detergents containing optical brighteners<br>soap<br>Body fluids (those are free)<br>sunscreen<br><br><br>
Body fluids (those are free) SICK!!!!!!!!!
In the good way, right?
I Hope So I Haven't Tried Jizz Yet Though
Honestly, tried with a black light, saw nothing, but I dunno.
What Using Jizz? It Shows Up Really Well
hey expertnoobz!<br> i need know one thing<br> <strong>the ink is visible under light of blue led?</strong>
I'm not sure, i don't think it would be. I would test it out, but I don't have any blue LED's at this time.
ok thanks <br>i will test it out when i go back to my house!<br>i'm travel and i still conected!
Cool, let me know what happens!
I know withought testing it that it does not work with a blue led.

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