Make amazing glowing fluorescent liquid at home using the insides of a yellow highlighter pen!

This is so easy to do!

Extracting the fluorescent liquid from a highlighter pen to make glowing fluorescent liquid is so easy, you should try it for an spooky themed science experiment.

This is so easy to do!


We did this at home recently and we were amazed at how bright the fluorescent liquid was. The kids loved it, just pouring it into the containers was really satisfying. We wrote secret messages with it and drew pictures too, which looked awesome under UV light! Fluorescein from these pens is safe to handle too – win:win! See how we did it and watch the video…..


Materials used

  • a yellow highlighter pen
  • water
  • pliers
  • protection for work surface
  • hand held UV blacklight (we have a UV lamp, but a torch worked too).




Here’s how I extracted fluorescein from a highlighter pen:

First I protected our work surfaces as this part was messy!

Using pliers I broke open the highlighter pen, removed the cartridge and popped it into the glass with some water.

After a few minutes, most of the ink had flowed into the water, but I gave the cartridge a good squeeze to make sure all the ink was out!

We switched on the blacklight and turned off the main light….and WOW! We had a lot of fun pour and playing with the fluorescein liquid n the UV lighting.



As you can see from the video we made some mess, but it was easy to clean up and left no stains.

This Glowing Goo can be used for more fun science – making fluorescent slime, glowing lava lamps, spooky orbeez


If you tackle this activity at home you do so at your own risk. If you have as much fun as we did, feel free to share your pictures with us on Facebook.

You could try other colours of highlighter pen, but we found the yellow ones worked best as they have a good quantity of fluorescein.


More free spooky science fun this Halloween

Head over to this tutorial to make Glowing Orbeez here or  Spooky Halloween Slime here (uses fluorescein), or gravity defying skeleton here, or you can BUY our Limited Edition Spooky Slime Kit here.

You can also check out the workshops we have coming up in Devon, why not book on?

Happy science-ing


Chief Scientist



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