Science
Making Oobleck
Mix just two ingredients to make a mysterious goop that flows like a liquid but turns solid when you squeeze it—and discover the science of non-Newtonian fluids.
Easy · 20 minutes
Introduction
Oobleck is named after a sticky substance in a Dr. Seuss story, and it is just as weird and unpredictable as it sounds. It runs through your fingers like water, but the moment you squeeze or hit it, it goes hard as a rock.
This activity explores a fascinating class of materials called non-Newtonian fluids, and it only takes two ingredients and a few minutes to make a bowlful of science you can actually hold in your hands.
The Why
Most liquids like water and juice flow at the same rate no matter how hard you push them. Oobleck is different because it is a non-Newtonian fluid, meaning its viscosity—how thick or runny it is—changes depending on pressure. When you push or hit the oobleck quickly, the cornstarch particles lock together and it behaves like a solid. When pressure is released, the particles separate and it flows like a liquid again. This property is called shear thickening, and engineers study materials like this for things like body armor and pothole filler.
Step-by-Step Instructions
- 1
Pour the cornstarch into the large mixing bowl.
- 2
Add the food coloring to the water if you want your oobleck to be colorful.
- 3
Slowly pour the water into the cornstarch, stirring as you go—do not add it all at once.
- 4
Keep mixing until the oobleck has no dry lumps and feels strange to stir.
- 5
Try poking the surface fast with your finger, then dipping your finger in slowly and notice the difference.
- 6
Pick up a handful and squeeze it tight, then open your hand and let it drip.
- 7
Talk about what you notice: when does it feel solid? When does it flow like a liquid?