The inks in highlighters are often fluorescent colours. That means they are bright and easy to see, and it also means that the ink glows under a black light. Highlighter ink can be used for many black light crafts such as glowing flowers, glowing water and even glowing fake blood for Halloween. To make highlighter ink glow in the dark without a black light, mix the ink with glow-in-the-dark powder and a little water. Removing the ink from the pen is a simple task, but can be a little messy on the fingers.
Remove the bottom of the highlighter pen. The bottoms of larger pens can be removed with your hands and fingernails by slipping your fingernail beneath the edge and prying off the bottom. Use a pair of pliers on smaller pens to break the bottom off.
Remove the long strip of foam from inside the pen. Sometimes the foam is coated in plastic, but not always. The foam absorbs the ink.
Squeeze the foam over a small container to release the ink. The ink will slowly drip out. Squeeze from the centre of the foam down to the bottom to release as much of the ink as possible. Turn the foam around to squeeze out the rest from centre to bottom. There is not a lot of ink highlighter pens. You will squeeze out a teaspoon or two at most.
Mix 2 tablespoons of water with the highlighter ink. Add 1/2 teaspoon of glow-in-the-dark powder and stir until it is fully dissolved. This mixture can be used as a watercolour paint and will glow after being in the sunlight and when under a black light.
Squeezing out the highlighter ink can be messy on the fingers. Be sure to wash your hands immediately after to prevent the ink from staining. One drop of highlighter ink is enough to colour 227gr of water. The water will glow under a black light. Place a carnation in the water and it will glow under a black light once it has absorbed some of the water.