Oobleck is a fascinating, yet simple, mixture made from combining ordinary cornstarch with water. It is recognized for its unique texture: it flows like a liquid but instantly resists movement when struck or squeezed. This strange behavior has made it a favorite subject for classroom science demonstrations and popular household experiments. Understanding this material requires examining both the history behind its memorable name and the physics that governs its duality.
The Literary Origin of Oobleck
While the cornstarch and water mixture existed previously, the name “Oobleck” was popularized by American author Theodor Geisel, better known as Dr. Seuss. Geisel introduced the term in his 1949 children’s book, Bartholomew and the Oobleck. This literary work provided the familiar moniker for the strange substance.
The book tells the story of the young page boy Bartholomew Cubbins, who must save his kingdom from a sticky, green goo summoned by the King’s royal magicians. This fictional Oobleck fell from the sky, wreaking havoc on the Kingdom of Didd. The imaginative story popularized the term, which eventually became the common name for the real-world cornstarch and water suspension.
The Scientific Identity
Scientifically, Oobleck is classified as a non-Newtonian fluid, meaning its resistance to flow, or viscosity, changes when shear stress is applied to it. Unlike water, which maintains a constant viscosity, Oobleck’s consistency is dependent on force. Specifically, it is a shear-thickening fluid, sometimes called a dilatant material.
The material acts like a liquid when the force applied is gentle or slow, allowing it to pour easily. However, when a sudden, high-impact force is applied, such as a punch or a rapid squeeze, the mixture quickly becomes rigid, acting like a temporary solid. This dual nature is caused by the cornstarch particles, which are solid and remain suspended in the water.
When force is applied quickly, the starch particles are pressed together, causing them to jam and form frictional contacts. This transient clustering locks the water into the gaps between the particles, momentarily preventing the mixture from flowing. Once the external pressure is removed, the particles relax, the water flows again, and the mixture reverts back to its liquid-like state.
Creating the Compound
Making Oobleck requires only two common household ingredients: cornstarch and water. The ideal consistency is achieved using a ratio of approximately 2 parts cornstarch to 1 part water by volume. For instance, a good starting point is mixing 2 cups of cornstarch with 1 cup of water in a large bowl.
The ingredients should be mixed thoroughly, initially with a spoon and then with hands, until a uniform slurry is formed. If the mixture is too fluid and does not solidify when squeezed, add more cornstarch incrementally. If the mixture is too stiff or powdery, a few drops of water will loosen it.
Disposal Warning
Oobleck should never be poured down a sink drain, as the cornstarch particles can settle and harden, causing clogs. The safest disposal method is to allow the mixture to dry out completely and then sweep the powder into the trash.