Manufactured in Sweden, Kinetic Sand sure looks like regular sand, and in fact, 98 percent of this novelty product is just that - sand. It’s the other 2 percent that gives it its strange properties - an ingrediant called polydimethylsiloxane. This very common silicon-based compound also happens to be a key component of Silly Putty - that stretchy, bouncy, rubbery substance every kid loves until it gets irrevocably stuck in the carpet.
By adding just a tiny bit of polydimethylsiloxane to some ultra-fine sand, Kinetic Sand becomes what’s known as a non-Newtonian fluid. Unlike Newtonian fluids, which have a constant viscosity that only changes as temperatures or pressures fluctuate (such as water freezing) and take on the shape of the container they’re placed into, non-Newtonian fluids follow their own set of rules. Also known as ‘strange liquids’, non-Newtonian fluids can change their viscosity under stress, such as when you shake them or hit them with a mallet.
Honey, for example, is a non-Newtonian fluid because the more you keep stirring it, the more liquid it becomes. Cream, on the other hand, becomes thicker the more you stir it. If you shake - and therefore increase the stress on - tomato sauce in a bottle, its viscosity will decrease, allowing it to flow better.
As a non-Newtonian fluid, Kinetic Sand acts like a viscous liquid, but also like an elastic solid. This is because the molecular structure of polydimethylsiloxane is held together by hydrogen bonds, a few of which can be easily broken when small amounts of stress are applied, allowing the sand to flow freely. When more stress is applied - say, when you’re cutting it with a knife - lots of hydrogen bonds are broken apart, allowing the substance to ‘tear’ into very neat pieces.