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Experiment

The Slime Lab

Cornstarch and water make a goo that acts solid when you punch it and liquid when you rest your hand in it.

Ages 3–1015–40 min1–3 kids

Mix cornstarch and water in a tray until it forms oobleck — a substance that resists a fast hit but flows around a slow, still hand. Punch it, squeeze it, let it drip through your fingers. There's no wrong way to play with it, and the physics is genuinely strange even to adults.

What you need

  • cornstarch
  • water
  • a shallow tray or bin
  • food colouring (optional)

How to do it

  1. 1Mix roughly two parts cornstarch to one part water in the tray, stirring until it thickens but still pours slowly.
  2. 2"Punch it as hard as you can — then try to just rest your hand in it." Let them feel the difference for themselves.
  3. 3Let it drip, scoop, and squeeze between fingers — the goo re-forms differently every time.
  4. 4Add a drop of food colouring partway through if attention starts to dip; it resets the novelty without changing the activity.

Variations

  • If they're hesitant to touch it: start with a spoon, then let them poke it with one finger before committing a whole hand.
  • How it ends: let it dry out on the tray overnight and crack it into pieces the next morning — a second, shorter activity that closes the first one naturally.

💡 Parent tip

Keep a towel under the tray from the start — it will end up on the floor, and prevention beats cleanup.

What your child develops

  • Non-Newtonian physics — a hands-on encounter with a substance that behaves differently under different forces
  • Cause and effect — fast force versus slow force produces opposite results, learned by feel rather than explanation
  • Sensory regulation — the resistance and give of the material is calming for many children

Safety notes

  • Not edible — keep away from children who still mouth objects. Wipe off skin with water, not soap, if it dries and tightens.

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