Oobleck (Cornflour Slime)

Supplies

• Cornflour (about 1 cup per child)

• Water (½ cup per child, approx.)

• Food colouring (optional)

• Large mixing bowl or tray

• Spoon or spatula (optional — kids will mostly use hands)

• Table covering or trays to reduce mess

Steps

1. Pour the cornflour

1. Tip about 1 cup of cornflour into a mixing bowl or tray.

2. Break up any lumps with your fingers.

2. Add water slowly

1. Slowly add ½ cup of water, a little at a time.

2. Mix with your hands as you go.

3. Stop adding water once the mixture:

   • Feels solid when you squeeze it, but

   • Flows like a liquid when you let go.

You may need to adjust slightly — more water if too powdery, more cornflour if too runny.

3. Add colour (optional)

1. Add 2–3 drops of food colouring to the water before adding it to the cornflour (to avoid stained hands).

2. Mix until the colour is even.

4. Play time

Kids can:

• Squeeze it to make it go hard

• Drop it and watch it splash

• Punch it (it becomes solid!)

• Let it drip through their fingers

Other Information

• Science link: Oobleck is a non-Newtonian fluid — it doesn’t behave like a normal liquid or solid. Pressure makes it hard; relaxing makes it flow.

• Clean-up:

  • Let any spills dry, then sweep/vacuum.

  • Never pour large amounts down sinks — it can clog. Bin it instead.

• Safety: Food colouring can stain surfaces; use trays or table covers.

• Extender ideas:

  • Add spoons, cups, or cookie cutters

  • Try walking across a large batch (older kids LOVE this!)

  • Try adding glitter for “galaxy oobleck”