Put enough water into a bowl of cornstarch ('cornflour' in the UK) so that it takes on the kind of consistency of that white glue you used in school. You now have a substance with some very odd properties. Specifically, it flows like a liquid normally but acts just like a solid when you put it under pressure. So, for instance, if you try to quickly jab at it with your fingers, it will stop you at the surface. But if you just push your fingers slowly, they'll sink in and you'll be able to touch the bottom of the bowl easily. You can take a bit of it between your two hands and start moving them. The stuff will react like a doughy solid, rolling into a firm tight ball. But as soon as you stop the rolling and hold it in the palm of your hand, the ball melts and runs out between your fingers.

This is because the finely ground particles don't actually dissolve in water the way that sugar or salt would. Instead, they remain dispersed in the water as particles. It's a 'suspension' not a 'solution.' It's still counter-intuitive and therefore really prim to play with.

Well, Kottke pointed to a YouTube video the other day of something I've always wanted to do. For a foreign television show, somebody made up a huge container of the stuff. Large enough for a person to jump into. Here's what happened.