Have you ever made oobleck? It’s a wonderfully weird activity that kids love — part science experiment, part sensory play, and completely fascinating to watch. Oobleck behaves like a liquid one moment and a solid the next, and once your child gets their hands into it, they won’t want to stop.
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What is Oobleck?
Oobleck is what’s known as a non-Newtonian fluid. In simple terms, that means it acts like a liquid when you pour it, but behaves like a solid when a force is applied to it — squeeze it and it feels firm, but let it rest in your open hand and it will ooze straight through your fingers.
The unusual name comes from the Dr. Seuss book Bartholomew and the Oobleck, in which a strange green, gooey substance falls from the sky and causes chaos in the kingdom.
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How to Make Oobleck
Watch the video above for a quick, easy-to-follow guide, then gather your ingredients and get stuck in.
Ingredients:
- 1 cup water
- 1.5–2 cups cornflour (corn starch)
- Food colouring (optional)
What to Do:
1. Put the water in a bowl and start adding the cornflour, stirring with a spoon to begin with. As the mixture thickens, you’ll need to switch to using your hands.
2. Once you’ve added about 1.5 cups of cornflour, start adding the rest more slowly. You’re aiming for a consistency where the oobleck feels solid and liquid at the same time.
3. If the mixture gets too thick or crumbly, just add a little more water.
4. When you’re happy with the consistency, add a few drops of food colouring and mix it in with your hands.
5. Now let your child have a good old play with it!
Things to Try with Oobleck
- Grab a handful, squeeze it, and then let it ooze out of your fingers.
- Drag your fingers slowly through it.
- Roll some oobleck into a solid-looking ball — then watch it melt back into liquid the moment you stop moving it.
- Jab at the surface quickly, then try slowly sinking your finger in instead.
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Frequently Asked Questions
Is oobleck safe for kids to play with?
Oobleck is made from just cornflour and water, so it’s a non-toxic, taste-safe activity for children to explore with their hands. As always, supervise younger children during messy play.
How do I clean up oobleck once we’re finished?
Because it’s mostly cornflour, oobleck dries out and can be swept or wiped away once it hardens. Avoid pouring large amounts down the sink, as it can clog drains — scrape it into the bin instead.
Can I store oobleck and use it again later?
Oobleck doesn’t keep well once it’s been mixed and played with — it tends to dry out or separate. It’s best made fresh each time, and it’s quick and cheap enough to whip up whenever the mood strikes.
Why does oobleck act like a liquid sometimes and a solid other times?
It’s a non-Newtonian fluid, meaning its thickness changes depending on the force applied to it. Sudden pressure (like a punch or a squeeze) makes the particles lock together and feel solid, while gentle handling lets it flow like a liquid.
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Save This for Later
Loved this activity? Bookmark or save this page so you’ve got it handy the next time you need a rainy-day activity or a simple science experiment for the kids.
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