Some science activities make kids stop what they’re doing and stare in awe.
This is one of them.
At first the jar looks calm.
Just oil floating over water.
But then the color begins to fall.
Tiny glowing streams drift downward through the jar,
stretching,
swirling,
bursting apart like fireworks underwater.
Under blacklight, the effect becomes even more dramatic.
The colors begin glowing brightly under blacklight, and the movement becomes slow enough for kids to really watch the reaction unfold.
This glowing fireworks experiment is simple to set up, incredibly captivating to watch, and perfect for summer science play, glow activities, or 4th of July learning fun.
If you love hands-on glow science, be sure to explore our glow activities for kids and oil and water experiments collection for even more glowing reactions and liquid density fun.
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Why Kids Love This Experiment
There’s something mesmerizing about watching the color slowly break apart and move through the jar.
The reaction feels almost magical under blacklight,
especially because the fireworks effect happens gradually instead of all at once.
Kids naturally begin asking questions:
- Why does the oil stay on top?
- Why does the paint fall through?
- Why do the colors spread like fireworks?
That curiosity turns this into both a sensory activity and a meaningful science invitation.
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Supplies for Glowing Fireworks in a Jar
You only need a few simple materials:
- Clear jar or cup
- Water
- Cooking oil or baby oil
- Neon liquid watercolors or fluorescent paint for blacklight play
- Small bowl
- Spoon
- Blacklight
Optional:
- Multiple neon colors
- Extra jars for color comparisons
How to Make Glowing Fireworks in a Jar
Step 1: Fill the jar with water
Fill your jar about 3/4 full with water.
Set it aside while you prepare the glowing color mixture.
Step 2: Mix the Oil and Neon Colors
Add 2–3 tablespoons of oil to a small bowl.
Then add several drops of neon watercolor paint or fluorescent liquid paint.
Use a spoon to gently stir the mixture.
The paint will not fully combine with the oil, and that’s exactly what you want.
Breaking the paint into smaller droplets helps create the fireworks effect later.
Step 3: Pour the oil into the water
Slowly pour the oil mixture into the jar.
At first the oil will float quietly at the top.
Then the magic begins.
The neon color slowly separates from the oil and drifts downward through the water in glowing streaks and bursts, creating a glowing density experiment kids can actually watch in motion.
Under blacklight it looks almost like underwater fireworks.
Our glowing oil and water experiment explores this same separation effect in a simpler but equally mesmerizing way.
Watch the Fireworks Spread
The glowing color continues falling through the water little by little, creating swirling patterns, soft bursts, and glowing clouds of color.
Every jar turns out slightly different.
Some create soft cloudy bursts while others form long drifting trails of color.
Some colors fall quickly, while others stretch and spiral slowly through the water.
That unpredictability is part of what makes this experiment so captivating for kids.
If your kids enjoy watching liquids separate and move, they’ll also love our homemade lava lamp experiment where colorful bubbles rise and fall through oil and water in a completely different way.
The Science Behind the Glowing Fireworks
This experiment works because oil and water have different liquid densities.
Oil is less dense than water,
which is why it floats on top.
The neon paint, however, is heavier than the oil.
As the paint separates from the oil, it sinks through the water below, creating the glowing fireworks effect.
This activity is a wonderful introduction to:
- liquid density
- oil and water science
- color mixing
- glowing sensory exploration
If your kids enjoyed this experiment, they’ll also love our:
Tips for the Best Glow Effect
- Use neon liquid watercolors for the brightest color payoff
- Dim the lights before turning on the blacklight
- Stir gently instead of aggressively
- Use clear jars with smooth sides for better visibility
- Try combining multiple neon colors in separate jars
Baby oil also works beautifully for this activity and creates a slightly different movement effect than vegetable oil.
You can also try this setup with our glowing water beads for an even more immersive blacklight sensory experience.
Extend the Play
Once kids finish observing the fireworks effect, try experimenting with:
- different oil types
- warm vs cold water
- additional neon colors
- larger jars
- glitter accents
- glow sensory trays or glow sensory bins nearby
Kids often continue experimenting long after the fireworks effect slows down, especially when the jars are paired with other glowing sensory materials.
More Glow Science Activities Kids Love
If your kids enjoyed this activity, try these next:
- Glowing Tornado in a Jar
- Glow Water Beads
- Glow Chalk Paint
- Glow-in-the-Dark Slime
- Glowing Ice Experiments
- Glowing Ice Paint
These activities work beautifully together as part of a larger glow science or blacklight sensory play unit. You can explore even more glowing sensory play, blacklight activities, and hands-on glow experiments in our full Glow Activities for Kids collection.
✨ Pin these glowing fireworks in a jar experiment for later and try it during your next glow science night, summer activity day, or blacklight sensory play setup!
