Glowing Water Science Experiment – Fluorescence

Glowing Water Science Expertiment

Glowing Water Bottles

This simple glowing water science experiment will help teach children about light waves and fluorescence.

It’s great fun!

They will be mesmerized by the glowing water and the use of darkness to perform the reveal really adds to the ambiance of the overall results. The glowing light experiment can be accomplished in a variety of ways but for ease and safety considerations we will concentrate on my two favorite methods.

What Is Black Light?

For this experiment, we will need to use a Black Light. Sounds contradictory I know, but a black light is simply a small light or handheld torch, that emits light from the Ultra Violet A (UVA) spectrum.

A Black Light can be purchased online or via your local hobby or hardware store. The cost is low and is a very useful item to have around the home. Not only is it an essential part of a home scientists arsenal but it is very handy when checking for stains on household carpets, floors, and stairs.

Equipment Required For Our Experiment

For our experiments, we will need the following items

    • A Black Light
    • 3 Small Glasses
    • A Jug Of Water
    • Tweezers
    • 3 Highlighter Pens (Different Colors)
    • A Dark Room to show the results

Let’s Get Started!

Firstly we need to extract the ink filled felt from each of the highlighter pens. They can be a bit difficult to remove so in the interests of safety, I would suggest that the adult takes care of this task.

The felt can normally be removed by twisting the tip of the highlighter pen away from the main body. In some models, the end of the pen can be lifted off by levering it away with a small knife. If both of these methods yield no results, then take a sharp knife like a box cutter and carefully push the knife through the body of the pen. When the knife is inside, carefully pull the knife along the body of the highlighter to split the case.

Put the felts from the three pens aside, ready to be used during the experiment.

Creating A Glowing Solution

Put a small amount of water into each of the 3 small glasses and place each of the highlighters felts into each glass. The amount of water in each glass doesn’t need to be specific but it is a good idea to put just enough water to cover the felt in each glass.

If you put too much water in ink from the felt will take longer to be absorbed into the water and the ink will be diluted by the water. The result will be a weaker solution and therefore a less spectacular glow.

Leave the felts in the water for a few minutes to allow the ink to dissolve. You will notice that the colored ink start to make the water a deeper color.

After a few minutes remove the felt from the water with the tweezers and discard the ink felts.

Time To Glow

Place the three glasses in your darkened room and set the Black Light about 12 inches away from the glasses. Gather the audience around the glasses and switch of the Black Light.

When the suspense has built up to a breaking point, switch off the room light and watch the expression on your children faces. They will be amazed by the glow of the water!

But Why Does The Water Glow?

The ink from the highlighter pens contains chemical compounds that are fluorescent. Yellow and green highlighter pens contain a chemical call Pyranine which is highly soluble in water.

Fluorescent chemicals have an interesting characteristic, which allows them to absorb energy from Ultraviolet radiation (invisible to humans) and then radiate that light energy at a longer wavelength. The longer wavelength is part of the light spectrum that is visible to humans.

Because the ultraviolet light cannot be seen in our experiment, the water containing the fluorescent chemicals looks as though it is glowing on its own.

Under everyday lighting conditions, the visible light reflected by the ink is added to the light energy converted by the fluorescent material. The highlighter ink is therefore physically brighter than normal ink.

Fluorescent chemicals and compounds are all around us. From obvious uses, in highlighter pens, high visibility jackets and road safety signs to an additive in washing powders and soap,

This is how they make your whites, whiter than white! If you look at dark clothing in the darkened room with your black light, you will likely notice tiny fluorescent flecks.

Simple Alternative Experiment – What A Tonic!

Glowing Tonic Water

Glowing Tonic Water

If you don’t want to go to the trouble of extracting the felt from highlighter pens, there is a very simple alternative experiment that allows you to show the results of fluoresces without the mess.

Simply take a bottle of Tonic Water and place it in the darkened room with the Black Light in proximity. When the room lights are turned off you will notice that the Tonic Water glows with a slightly bluish color.

The fluorescent nature of the Tonic Water is due to the addition of Quinine as a flavoring. Quinine is compound that when added to Tonic Water to give it its distinctive bitter taste.

Is Light Always Visible?

A simple experiment like the Glowing Water Science Experiment is a fantastic way to help you explain a complex scientific theory in an easy to understand, visual way. The hands-on nature of this experiment make, it an enjoyable experience for children and parents alike, by bringing science to the home.

We learned that light has a wide spectrum and not all of that spectrum is visible to humans. In addition, we were able to understand that light waves can be absorbed by fluorescent materials and emitted as visible light, thereby physically making the material much brighter.

What Do You Think of This Experiment?

At, I endeavor to help adults and their children to get hands-on with science experiments. The aim is always to strike a balance between simple, result driven experimentation and the need to explain the result in an easy to understand way.

I really hope that you enjoy this experiment with children!

If you have any suggestions, feedback or questions, I would be more than happy to take the time to reply to your comments.

Best Wishes!



  • Love this idea, Nick! My 4 year old daughter may not understand the whole idea of fluorescence, but I think she’ll still appreciate the glowing water, and LOVE the actual process of doing the science experiment together!
    I’ve actually never seen a black light before – do I just find them in the lighting department at the local hardware store? Or can you recommend one I can purchase online? They sound fun, regardless!

    • Thanks for the comment Marlaine and welcome to my site! You picked up on the process of spending time with our children and that is really important. Promoting family time and sharing a learning experience is what really drive me to build this website.
      Black Lights can be picked up at your local DIY store or Walmart etc. A huge application for Black Lights is stain detection. Amazon has a large selection over a large price range.

      For experiments, a small hand held torch is adequate and can cost under $10.
      I will be reviewing Black Lights with a few recommendation in the coming few days, so please come back and take a look. Thanks again for your great comment.

  • hi Nick,wow what a fantastic experiment can’t wait to try it out with my kids

    • Hi Hamid,

      Many thanks for stopping by and taking the time to comment. A really important part of the experiments is the quality time we spend together with our children.

      Please come back again to see our new experiments! A lot more to come.

      Many Thanks

  • Great experiment Nick. I’m continually looking for fun activities to with my kids and we’ll be trying this one on the weekend.
    Are black lights readily available at the hardware store?

    • Hi Vince – Thanks for the comment! I hope you enjoy the experiment and get some real quality interaction with it.
      Black lights are available at hardware & DIY store or from Walmart & Target. You should be able to get a small handheld one for under $10, you don’t need to spend a lot of money. Please let me know if you need a recommendation.

      Come back and see my Black Light review in the coming days.

      Appreciate you stopping by!

  • What a great experiment! I’d love to do this with my daughter. She is also too young to understand what’s going on, she’s 3.5 years old but she will love it. So thank you.

    By the way do you have any experiments that would be suitable for her age? Thanks.

  • This is so cool! I am happy to have stumbled upon it. I am going to check out the rest of your site now, thanks!

    • Thanks for the dropping in Tara and appreciate your comment.
      Please check back in the next few days as I will be adding more experiments every week.

      I will also be performing reviews of science equipment and kits that are suitable for the home. If you would like to see something specific or have any questions please either comment here or contact me directly.

  • Fantastic site your experiments are a great introduction into science for young curious minds. Keep me coming, Because my grandchildren first words after they complete there first project will lets do another one.

    • Hi Maurice, great to hear from you and so glad your grandchildren enjoyed the experiment. I will be adding more experiments regularly so please check back often. Check out my other posts on Growing Crystals and Floating Eggs. Both are very simple and engaging at the same time. Would love to hear how much they enjoy those too!

  • Wim Bollen

    Cool, enlightening!

  • What an amazing experiment, can’t wait to try it with my 7 year old nephew. Educating children with such experiments encourages the child to learn more. It will help them understanding the subject better.
    Thank you Nick for sharing this experiment, it’s really helpful for a lot of children.

    • Thank you so much for taking the time to comment.
      I hope your nephew enjoys it and you come back to read about our other experiments.

  • Fun experiments! I will pass on to some teacher friends of mine.

  • Nick, I found this experiment fascinating – wish I could have shown this to my daughter when she was a child. But wait, I do have grandsons who are young. Maybe I’ll have a chance to show this to them. They will be awed by it, I’m sure. Nice blog site with some very cool information. Well done. – Shirley

    • Hi Shirley, thanks for stopping by and taking the time to make a comment.
      It’s great that you can do this experiment with your grandsons! They will love it!

  • Ronnie Jordan

    Very good experiment to show the kids. Gets their interest peaked in science. I do have a question. Are you telling me after you put the ink in the water it is clear or is it distorted and glows with the black light being added?

    • Hi Ronnie, Thank you for the comment and that’s a great question! The color of the water changes to a similar color as the ink but it will only glow with the addition of the black light. The fluorescent particles in the ink actually glow brighter.

  • Damn this is impressive and quite simple! I might show my brother this as he’s still in school and may need to do a scientific experiment soon, i’ll show him this as he may be interested!

    Thanks for the great article:) I like the easy to follow steps too!

    • Hi Jeremy, thank you for the comment. I think it’s important that the steps are simple. Long form instruction can lead to boredom and loss of interest. They are supposed to be fun after all. Please come back and check as I add more experiments.

  • This is an interesting post. I learn something new today. I had no idea about what is black light and how the water glow. Thank you for filling me up today and keep it up. Cheers!


    • Hi Jaden – Thank you for connecting and leaving a comment. Glad to hear that you learned something about a Black Light.
      They are really useful around the home!

  • This is a wonderfully simple and expertly explained science experiment
    amazingly enough I hadn’t heard of the concept of black light so I’ve learned something new

    science experimentation was never a strong favourite of mine during my school days [maybe it had something to do with a crazy and wicked teacher]

    congratulations Nick

    • Thank you for your kind words Oliver and thank you for taking the time to comment. It does seem to happen quite often that children haven’t enjoyed experiments so much in the past, due to a teacher. We are trying to change that and bring the fun back to science for kids!

  • Hi Nick, I can imagine the expression on my nephew’s face if we can try this one day. He’s very curious about things and would love these experiments, although sure it’s gonna be messy. I’ve watched a video from astrophysicist Neil DeGrasse Tyson where he was talking about kids being born scientists, but their curiosity and dream of exploration were suppressed by parents who’d rather keep the order in their household. Parents can start reviving that curiosity through your experiments here. Very worth sharing. 🙂

    • Hi, King Kong’s Girl – Thank you so much for the feedback! You are right, it’s can be difficult for parents to let go and embrace the need to focus on the enjoyment and learning, rather than need to keep order.

      At we like warn readers where there is likely to be some mess or spillage and perhaps advise that an experiment should be performed outdoors. For instance, the Mentos Soda Science Experiment (

      Even so, it is disheartening for a child than to have that enthusiasm and desire to explore science suppressed in favour of order. Exploration and examination is the cornerstone of learning.

      Interestingly, I am halfway through an article on Neil’s work to be posted here at the end of June. I hope you enjoy it!

  • You explain the experiment so well, even I can understand. The scouts will love this one, can’t wait to show them. Thanks you for sharing this.

    • Hello Irene, Thank you for your comments!
      If there are any science topics you particularly like to see included in your scout group, please let me know.

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