“100” Fireflies in a Jar

This activity was chosen to celebrate our 100th straight day of STEM Play. When deciding how to mark this special occasion, there was no shortage of suggestions.

My husband wanted to make homemade sparklers. Although this is totally do-able, given that I have an unofficial rule against fire and explosives, I had no choice but to veto this idea. Such disappointment (for him, not me).

The next problem was our 100th day fell on a Monday, a school day. Only one idea made sense. Do something with GLOW STICKS!

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I wanted to stress the PLAY part of STEM Play Every Day. What could be better than playing with glow sticks, just because and DURING THE DAY!

We snapped them into action and played inside our dark room (aka our windowless bathroom) because the sun was still shining. The most challenging part was deciding which glow sticks to pick out of the package!

100th day celebration with glow sticks. Photo: © Susan P. Yates

Then we did our super short experiment, different temperatures and glow sticks. Does anything happen? Yep, it sure does! But today was all about the fun, so I’ll save that story for another day.

Fireflies in a Jar. Photo: © Susan P. Yates

So after playing, after our experiment, we had all these glow sticks, well, glowing. The next logical step was to cut them open, right? Learn how they work! We called this one “fireflies” in a jar. Because that’s what they looked like! Then my daughter yelled out “Fireflies are chemical bugs!”.  She’s definitely my child.

Needless to say when my husband came home to discover us making a mess in the “dark room” he just shook his head and walked away. We didn’t really notice because we were having WAY too much fun!


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Required Materials:

  • Glow sticks
  • Scissors
  • Gloves
  • Jar with lid
  • Paper towel
  • Dark room


  • Preparation/Experiment:  10 minutes
  • Observations and Results:  As long as you like (or until the glow fades)


  1. Set up your work space. It’s going to get messy. We put down lots of paper towels on a little table.
  2. Pick the glow sticks you want. Different colours are best.

    Our “unactivated” glow sticks. Photo: © Susan P. Yates
  3. Snap and shake your glow sticks to get them glowing!

    Glowing, glow sticks Photo: © Susan P. Yates
  4. With a pair of scissors (and gloves!), cut the plastic end off the glow stick. (The glow liquid may start to come out immediately so be sure to do this over the jar you are using).

    Cutting off the end of the glow stick. Photo: © Susan P. Yates
  5. You may need to shake the glow stick contents into the jar or just let it just drip out if you are patient.

    Letting the contents of the glow stick drip into the jar. Photo: © Susan P. Yates
  6. Be careful! Some of the glass from inside the glow stick may come out.

    View of the broken glass that came out of the glow stick. Photo: © Susan P. Yates
  7. Once you have collected the glow liquid. Close the jar lid tightly then SHAKE to splatter the glow liquid around inside the jar. You don’t need a huge amount of liquid to produce the firefly effect.

    (Left) After collecting the glow liquid. (Right) After shaking the liquid in the jar with lid. Photo: © Susan P. Yates
  8. Turn off the lights and enjoy the show!
Fireflies in a Jar. Photo: © Susan P. Yates

Tips and Tricks

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We had the long skinny glow sticks (you know the ones for making bracelets and necklaces). It was actually quite challenging to get the liquid out. I think the thicker ones might be better but we didn’t try those because that would mean a trip into town.

I didn’t wear gloves when cutting open the glow sticks. Big mistake. I won’t make that mistake again. The liquid squirted out much faster than I had anticipated. Good thing we were in the bathroom, so I could wash up very quickly. Definitely an adult step.

If you decide to “shake” or “flick” the glow stick liquid into the jar, do so VERY gently. You don’t want these chemicals splashing around or ending up on you or your walls or your floor. And be aware that there is glass inside, broken glass! I tried to keep everything contained in the jar. And clean up any spills immediately. This is no joke!

Speaking of chemicals and spills. If you get any on you, WASH IMMEDIATELY with soap and water. These are chemicals (read the label on your packaging!). Preparing outside would be a good idea. I would advise getting an adult to do all the steps until you reached the “jar is tightly closed with the lid” step.

Use a jar you can throw out. You shouldn’t use these jars again for anything else. We used old spaghetti sauce jars not my good mason jars.

Science Secrets Revealed

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Glow sticks are a smart design. Have a look at the glow stick BEFORE you activate it. When you invert it, or shake it, you will see the coloured liquid move around. This liquid is made up of two different chemicals. One is usually diphenyl oxalate and the other one is the dye. The type of dye decides which glow colour you will see.

Do you remember the CRACKING sound you heard when you SNAPPED the glow stick? Did you know you were breaking glass? There is a thin glass capsule inside the plastic glow stick! Can you see it? It might be hard to see! When you break the glass you release ANOTHER chemical, something called hydrogen peroxide, that was trapped inside this glass.

After you SNAP the glow stick, we all know to SHAKE it up to get the glow going. You are actually mixing all these chemicals! You are starting a chemical reaction!

Remember the diphenyl oxalate I told you about? Well, this chemical and the hydrogen peroxide when they get together will change into different chemicals. One of these new chemicals, called a peroxyacid ester, isn’t very stable, it’s not very happy being a peroxyacid ester. It would rather be something different. It’s like putting two cats together who do NOT like each other. These cats want to break away from each other and FAST.  The peroxyacid ester, splits itself in half ALL by itself (that’s how unhappy it is being this ester)! During this ‘split’ a gas called carbon dioxide is produced along with LOTS of energy! This energy finds the chemical dye inside the glow stick and gets the dye all excited.

If you read our experiment called (Glowing) Ice, Ice Baby, you already know all about what happens next – it’s fluorescence!

Some molecules, like our glow stick dye, absorb energy, when this happens they become excited. Think of a kid who has eaten way too much candy and is on a huge sugar rush and bouncing around the house like crazy! Thankfully, that kid will eventually return to ‘normal’ after the sugar wears off. So do excited molecules, they want to return to their normal low energy state (they want to be like a “couch potato”). Now the kid who ate way too much sugar probably got rid of the ‘extra’ sugar energy by releasing it in the form of high energy play. Molecules also need lose this extra energy. Fluorescent molecules, like our glow stick dye, release this energy in the form of light (which is actually a form of energy!). This light energy is the “GLOW” in glow stick! Amazing!

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One thought on ““100” Fireflies in a Jar

  • July 28, 2016 at 7:05 PM

    I can’t wait to try this on our next camping trip! I love the science lesson here too. I had no idea that the “cracking” sound was glass. 🙂


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