Water and oil, and some other simple fluids, respond in the same way to all levels of shear stress. These are termed Newtonian fluids, and their viscosity is constant for all stresses although it will ...

But for non-Newtonian fluids like oobleck, the viscosity changes when a shearing force is applied. Ketchup, for instance, is a shear-thickening non-Newtonian fluid, ...

Normal, Newtonian liquids, like water, ... Custard, meanwhile, has the pouring, flowing characteristics of a fluid until you tap it with a spoon, when it turns near solid: it is 'shear thickening'.