Easy Glowing Orbeez Halloween Science

Halloween is just around the corner so how about some easy Halloween Science you can do at home?! These glowing Orbeez are fab for Halloween Science or, to be honest, at any time of year! They are so easy to make at home using the ink from highlighter pens, which contains a compound called fluorescein that glows (fluoresces) under UV light. A safe and easy experiment that the children loved especially at this spooky time of year.

Watch the video here or read on for more hints/tips and video tutorial.

Halloween Science Glowing Orbeez


perfect for Halloween!



  • Glass jars with about 200mls of water in
  • Different coloured highlighter pens (we found yellow worked best)
  • Pliers or something similar to help you remove the ink cartridge from the pen
  • Protection for your work surface
  • Clear Orbeez (also known as water beads)
  • UV blacklight (torch or lamp – we used a UV lamp)





First we needed to extract the ink (the fluorescein) from the cartridges.

I protected our work surfaces and using pliers I broke open the highlighter pen, removed the cartridge and popped it into the glass with about 200ml of water, and let it sit for a couple of hours. I also squeezed the cartridge to help get as much ink out as possible. This ink contains the fluorescent compound, fluorescein. I used a separate container for each different coloured inks we were using. We tested yellow, green, orange and pink highlight pen inks.

You can use the extracted fluorescein in many way, not just with Orbeez, here are 2 examples that we have done recently: Spooky Liquid & Halloween Slime

Now we add the Orbeez to make Spooky Glowing Orbeez. This part is easy – I just added a handful or Orbeez to each container and let them sit overnight to swell up.

The next morning I found all the water had been absorbed, and the Orbeez were huge! However, I noticed that the pink and orange inks had left a deposit behind on the Orbeez and in the bottom of the jars, so I gave all Orbeez a rinse under running tap water in a sieve.


I popped them back into their corresponding jar, and took them to a darkened room where we switched on the UV lamp….and WOW!


We could see instantly that yellow fluoresced the brightest because the yellow ones have the highest quantity of fluorescein in. So we concentrated playing with our yellow Orbeez, and ended up mixing the others together to see what happened.


You can see the yellow Orbeez glowing the brightest

Check out the video below to see what we did and how!



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.

Make glowing slime with your fluorescein!

Check out how to do it here!

If you try these activities at home you do so at your own risk.

You can also check out our Online Science Clubs for children aged 5-11, start in November 2020. £45 for a 5 week course, and we send you the kit! Bookings for these close on 22nd October.

Happy science-ing


Chief Scientist


Bye for now


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