You can make oobleck with just cornstarch and water, and it behaves like both a solid and a liquid when you play with it.

Quick Scoop

What you need

  • 1.5–2 cups cornstarch (cornflour)
  • 1 cup water
  • Food coloring (optional, for fun colors)
  • A mixing bowl and a spoon (or just your hands)

Basic recipe: how to make oobleck

  1. Pour the water into a bowl. If you want colored oobleck, stir a few drops of food coloring into the water.
  1. Start adding cornstarch slowly, stirring as you go. Aim for about 2 parts cornstarch to 1 part water overall.
  1. Switch to using your hands once it gets thick; it’s easier to mix that way.
  1. Adjust the texture:
    • Too runny: add a bit more cornstarch.
 * Too dry or crumbly: add a few drops of water.
  1. It’s ready when it feels hard if you squeeze or tap it quickly, but flows like a liquid when you relax your hand or move slowly.

A simple test: Roll some into a ball in your hand, then stop squeezing. It should suddenly melt and drip through your fingers.

Fun ways to play

  • Punch or tap the surface quickly: it will feel solid and “bounce” your hand or spoon.
  • Press slowly: your fingers or spoon will sink in like a liquid.
  • Let it ooze between your fingers like slime or “swamp goo.”
  • Add a Halloween twist with green coloring or toy eyeballs for a spooky effect.

Clean‑up and safety

  • Oobleck is for play, not eating.
  • Don’t pour big amounts down the sink; scrape it into the trash and rinse the rest with plenty of water so it doesn’t clog pipes.
  • If it dries out while you play, you can revive it with a few drops of water.

TL;DR: Mix roughly 2 cups cornstarch with 1 cup water (plus optional food coloring), adjusting until it’s stiff when you hit it but runny when you let it sit.