oobleck and glurch

I came across this completely (well, to me anyway) fascinating clip on YouTube today: inauspicious beginnings with some bloke stirring a petri dish of cornstarch with a pencil, but it gets seriously weird towards the end. The crazy phenomenon in the last phase of the experiment is called the "Lovecraftian tentacle effect", apparently, a perfectly apt description (assuming you've read some Lovecraft).

It's all to do with non-Newtonian fluids, which display counter-intuitive effects like getting thicker when you stir them (and then thinner again when you stop). The cornstarch one (try mixing a load of cornflour with some water) is used in school science lessons to illustrate non-standard liquid behaviour. It's colloquially called oobleck, apparently, and is often used for teaching purposes in conjunction with another non-standard liquid called glurch. Great names! A note of caution though: section II of the article perpetuates the myth about glass windows thickening at the bottom over time because of the glass flowing like a (highly viscous) liquid. This is generally accepted not to be true - if you want an interesting example of a true super-viscous liquid try this.

If you make custard with cornflour, you can walk on it, as this clip proves. Just don't stop or you'll sink.