Fake Cloud
Every version of this experiment tells you it shows how rain falls from clouds. Every version is wrong — and that makes it twice as interesting. The colour trails are real. The science behind them is something completely different from rain,
5-12 yrs
Easy
15
min
Stage 1-3
Mission Briefing.
Designed by Darin Carr (BSc, DipEd)
NESA Accredited Teacher Chemistry & Physics Specialist
Creator of the LAB™ Learning System
Essy
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Fake Cloud
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NESA Accredited Teacher
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High school chemistry & physics specialist 30+ years
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The Crazy Scientist in primary schools — 15 years
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International conference presenter on science education
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Creator of the LAB™ Learning System
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Curriculum aligned: NSW Science & Technology K–6 (2024)
A picture is worth a thousand words — check this out and see if you can spot the science hiding in plain sight.
Mission Equipment
A tall clear glass or large jar
Water
Shaving cream (foam, not gel — the foam structure is essential)
Food colouring — at least 3 colours for the full visual effect
A dropper or pipette (for precise, slow drops)
A spoon to level the shaving cream surface (optional)
Let’s Investigate
1
Fill the glass
Fill your tall clear glass about two-thirds full of water. Set it on a flat surface where students can see through the side.
3
Add your first colour
Using a dropper or the tip of a food colouring bottle, release one small, slow drop of colour onto the surface of the foam.
Then stop. Watch it carefully — follow it from the moment it lands until it stops moving completely.
2
Add the foam
Spray a generous layer of shaving cream onto the surface of the water — about 3 to 4 cm deep.
Use a spoon to level the surface gently so it sits flat. The foam should float cleanly on the water with a visible boundary between them.
4
Add more colours
Now add more drops — different colours, different spots across the foam surface.
Use a slow, deliberate technique for each one. Watch each drop find its own path through the foam
Did it work? Share the science! Tag @the_crazy_scientist on Instagram — we love seeing your experiments!
The Crazy Scientist LAB Learning System™
Every experiment follows The Crazy Scientist Lab Learning System™ — a simple way to help kids think like real scientists.
We
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LINK to what they already know,
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ACTIVATE curiosity through hands-on discovery
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BUILD understanding that actually sticks.
You already know that rain comes from clouds. And if someone asked you how — most people would say something like: the cloud fills up with water until it gets too heavy to hold, and the water falls out as rain. That explanation sounds reasonable. It gets repeated everywhere.
Here's your prediction before you touch anything: you're going to drop food colouring onto shaving cream floating on water.
You're predicting two things: what you think will happen — and whether you think this experiment actually shows how rain forms.
Write both predictions down. Then do the experiment. And then ask the question nobody in the room is asking.
Watch a single colour closely from the moment it lands on the foam — follow it all the way until it stops moving
Try adding colours slowly and carefully to different spots on the surface — watch whether they interact
The colour didn't sit on top and suddenly fall when the foam was "full." Describe exactly how it moved — was it a sudden drop or a gradual journey through something?
Look at the foam layer itself while the colour is moving through it. What does it look like from the side? What does that tell you about the structure of shaving cream?
You've just watched a liquid move through a porous structure and emerge on the other side. That process has a name: percolation. And it's running the world in ways most people never think about.
When rain falls on soil, it doesn't stay on the surface forever — it moves downward through tiny gaps in the ground until it reaches rock layers it can't pass through. That's how underground rivers and aquifers form. How is that the same thing you just watched?
A coffee filter is a porous medium — water passes through but the coffee grounds stay behind. What was acting as the porous medium in your experiment — and what was being filtered?
"Want the full teacher guide? The Crazy Scientist Lab includes classroom delivery tips, how to manage the WOW moment, differentiation for Stage 2 & 3, — ready to teach tomorrow."
Think Like a Scientist
Scientists don't just do ONE experiment; they change one part of the experiment (independent variable) and then see how it affects another part of the experiment
(dependent variable)
Change ONE variable and test again.
Does the depth of the shaving cream layer change how long it takes for the colour to break through — does a thicker "medium" slow the percolation?
Does the concentration of food colouring change how it moves — does more concentrated (denser) colouring percolate faster than a diluted drop?
🧪 Try it! Change ONE thing and test again. What did you discover?
Dr Puddledrip’s Science Tip
Want to go deeper? Tap a section below to explore. ▼
The Science Behind It
Here's what every other version of this experiment gets wrong: shaving cream is not a cloud, and this is not how rain forms.
Real clouds are not sponges. They don't hold liquid water and release it when they get too full.
A cloud is a suspension of microscopic water droplets — or ice crystals — floating in air.
So what IS this experiment showing? Percolation.
Shaving cream is an aerosol foam: a porous matrix of tiny soap-coated air bubbles, packed together with small interconnected channels running between them. It's not solid — it's riddled with tiny gaps.
Food colouring is water-based and denser than the foam. When you place it on the surface, gravity begins pulling it downward through those tiny channels, squeezing between the bubbles, moving through the foam the way water moves through soil.
When the food colouring reaches the boundary between the foam and the water, it breaks through and streams downward — producing the colour trails that look so dramatic. The colour is heavier than the water it enters, so it sinks and diffuses as it falls.
Extension: G&T Years 5 & 6
Vocabulary
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READY TO TEACH THIS
TOMORROW?
Running the experiment is easy; however, teaching it well is another challenge.
Teachers often ask:
How do I adapt this for Stages 1,2 or 3?
What do I do with fast finishers?
What misconceptions will they have?
How do I structure this for a full class?
What syllabus outcomes does it cover?
What do I say when they ask WHY?
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