The recipe for this one is super easy...
2 parts cornstarch to 1 part water
food coloring as desired
This is a wonderfully fun substance to play with. It acts like a solid when you add pressure and a liquid when you don't. Adding the cornstarch to the water changed the reaction time of the liquid. Usually liquids move so quickly we do not notice how long it takes them to move. Oobleck has a finite reaction time. We can see how long it takes for it to react. We can make oobleck act like both a solid and a liquid. A liquid like this is called a non-Newtonian fluid because it does not follow the rules that Newton discovered most liquids follow. A non-Newtonian fluid has properties of both a solid and a liquid and reacts to stress with increased viscosity. Cornstarch (amylose) and water can be considered a colloidal suspension. A colloidal suspension is a two-phase system in which the starch and water are not dissolved but simply mixed into a permanent suspension that will not settle on standing.