To make oobleck, slowly mix 1 part water to 2 parts of cornstarch in a bowl until the mixture has a gooey texture. The oobleck mixture is ready when it behaves like a solid and a liquid. Food coloring may be added to the water prior to mixing.
Oobleck gets its name from the Dr. Seuss book “Bartholomew and the Oobleck,” which tells the story of a king who is bored with the weather until a green sticky substance falls from the sky. The oobleck will behave like a solid at times, as it can be picked up and rolled around in a person's palms. Once the person stops rolling, the mixture turns to liquid and pours through the fingers. Applying pressure to the mixture increases its viscosity, or thickness, so tapping the surface of the mixture quickly feels like a solid. This action forces the corn starch molecules together so the mixture feels hard.
The amount of pressure applied to the oobleck determines its behavior. Relax the pressure and the corn starch molecules spread so the mixture becomes a liquid. The surface tension of the water prevents it from completely separating from the corn starch granules. Oobleck is an example of a non-Newtonian fluid because it lacks a consistent viscosity.